Group Title: study of molecular compound formation between dinitrogen tetroxide and some sulfur-containing Lewis bases
Title: A Study of molecular compound formation between dinitrogen tetroxide and some sulfur-containing Lewis bases
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Title: A Study of molecular compound formation between dinitrogen tetroxide and some sulfur-containing Lewis bases
Alternate Title: Molecular compounds formation between dinitrogen tetroxide and some sulfur-containing Lewis bases, A study of
Dinitrogen tetroxide and some sulfur-containing Lewis bases
Lewis bases, A study of molecular compound formation between dinitrogen tetroxide and some sulfur-containing
Physical Description: v, 97 l. : illus. ; 28 cm.
Language: English
Creator: Whitaker, Robert D
Publication Date: 1959
Copyright Date: 1959
 Subjects
Subject: Nitrogen compounds   ( lcsh )
Sulfur   ( lcsh )
Chemistry thesis Ph. D
Dissertations, Academic -- Chemistry -- UF
Genre: bibliography   ( marcgt )
non-fiction   ( marcgt )
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Thesis: Thesis - University of Florida.
Bibliography: Bibliography: l. 95-97.
Additional Physical Form: Also available on World Wide Web
General Note: Vita.
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Bibliographic ID: UF00098005
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: alephbibnum - 000424002
oclc - 11062892
notis - ACH2407

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A STUDY OF MOLECULAR COMPOUND

FORMATION BETWEEN DINITROGEN

TETROXIDE AND SOME SULFUR-

CONTAINING LEWIS BASES









By
ROBERT DALLAS WHITAKER









A DISSERTATION PRESENTED TO THE GRADUATE COUNCIL OF
THE UNIVERSITY OF FLORIDA
IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE
DEGREE OF DOCTOR OF PHILOSOPHY










UNIVERSITY OF FLORIDA
August, 1959

















ACKNOWLEDGMENTS


In a very real sense, all of the author's associates and

friends have aided him in the completion of this work. However,

there are a few individuals whose help has been indispensable.

Dr. Harry H. Sisler, the author's advisor, has directed this

work from the outset. For his patient guidance, gratitude is

sincerely expressed.

Mr. P. J. Thompson and Mr. Cal Workinger are responsible

for the construction of the special glass and mechanical equipment

used in this work. Their ingenuity is reflected in many of the

experiments described in this work.

Mr. Nathan L. Smith has, upon many occasions, made helpful

suggestions concerning laboratory techniques and has often aided in

lifting the sometimes slightly sagging morale of the author.

















TABLE OF CONTENTS

Page

ACKINOTWLEDMETS ... . . . . . . . . . .o ii

LIST OF TABLES. .o . . . . . o o o * * * * iV

LIST OF FIGURES . . . . . . . . . . . . v

INTRODUCTION. . . . . . . . o . o .. o o o o o 1

HISTORICAL REVIEW . . . .. * a * 5

EXPERIMENTAL PROCEDURES . . .. . . . . . . . 15

RESULTS o . . . o o o .o .. o o o * * * * 35

DISCUSSION. . . . . . . . . . . . * 50

SUMLIEART ..... . . . . . . . 82

APPENDIXES. .. s. o o o o o o o o o a o o o o o e o s o o 86

LITERATURE CITED. . . . . o o o s o o o o o o o o 95










LIST OF TABLES


Table

1. Compounds Obtained Commrcially. * * * * *

2. System: Dimethyl Sulfide Dinitrogen Tetroxide. . .


System: Bis-(chloromethyl) Sulfide Dinitrogen Totroxide.

System: Diethyl Sulfide Dinitrogen Tetroxide . *

System: Di-n-propyl Sulfide Dinitrogen Tetroxide . *

System: Di-n-butyl Sulfide Dinitrogen Tetroxide. . .

System: Di-isoaryl Sulfide Dinitrogen Tetroxide. . .

System: 1,4-Dithiane Dinitrogen Tetroxide. . . .

System: n-Butyl Ether Dinitrogen Tetroxide . .* .

System: Tetrahydrepyran Dinitrogen Tetroxide . .

System: 1,h-Dioxane Dinitrogen Tetroxide . . .

Freezing Point Depression. * * * * * *


13. Relative Polarizations of the Sulfide Dinitrogen
Tetroxide Addition Compounds at -60o. . . .

14. Electric Moment Data for Some Sulfides and Ethers .

15. Apparent Stoichiometry of the Sulfide Dinitrogen
Tetroxide Compounds in Chloroform Solution from
Dielectric Constant Measurements . . .


. .

*000



* .


Page

19

36

36

37

38

39

4o

41
hIi

42

42

46


62

63



73


3.

4.

5.

6.

7.

8.

9.

10.

11.

12.

















LIST OF FIGURES


N2OL Transfer Cell. . . . . .

Dielectric Constant Measuring Cell. ..

Top of Dewar Flask. . . . . .

Apparatus for Preparation of Standard N20

Freezing Point Cell . . .

Glass Reaction Apparatus . . .

Dimethyl Sulfide-Dinitrogen Tetroxide .

Diethyl Sulfide-Dinitrogen Tetroxide. ..

Di-n-propyl Sulfide-Dinitrogen Tetroxide.

Di-n-butyl Sulfide-Dinitrogen Tetroxide

Di-isoanyl Sulfide-Dinitrogen Tetroxide


SSolutions....
. . . . .









. . .


Figur<

1.

2.

3.

U.

5.

6.

7.

8.

9.

10.

11.


Page

17

22

24

25

30

33

43

43

1k

14

45
















INTRODUCTION


It has been known for many years that the products of reactions

between dinitrogen tetroxide and various organic compounds vary

according to the solvent used. For example, in the absence of a

solvent, or with petroleum ether, the following reaction leads to

the formation of approximately equal amounts of products I and II.


CH3 CH3 CH3

C = CH CH3 N20 CH3 C--- CH CH3 + CH3 C---- H CH

CH3 ONO2 NO ONO NO2

I II

However, if diethyl ether is used as a solvent for the reaction,

product II is predominant. Similar differences in products are noted

with other solvents (1).

Since many common solvents are Lewis bases, and since dinitro-

gen tetroxide is a Lewis acid, it was reasonable to think that molecu-

lar addition compound formation between Lewis base solvents and dinitro-

gen tetroxide could perhaps be at least partially responsible for the

observed facts.

During the last decade, there has been considerable work

on the formation of addition compounds of dinitrogen tetroxide with
1











2

ethers, amines, and aromatic hydrocarbons and their derivatives. It

has indeed been found that such molecules form addition compounds with

dinitrogen tetroxide (2). From the work that has been done, it appears

that dinitrogen tetroxide functions as a Lewis acid in one of two ways:

(a) as an undissociated molecule,

o 0

0' 0.

where one or two doner molecules, B:, can attack the nitrogen atoms,
+B

N-N
-0t *a+0
or, (b) as an ionic species after dissociation,
or, (b) as an ionic species after dissociation,

N201 --- NO+ + NO3-

where the ) + ion may be attacked by one or two donor molecules,

+ +
Bt_ N' :O or Bf-> I:p^

B

The nitrogen nitrogen bond distance i.n dinitrogen tetroxide
0
is 1.64 A, as compared to 1.47 2 in hydrazine (2). Thus unusually

long nitrogen-nitrogen bond distance in dinitrogen tetroxide affords

a favorable steric condition for the increase in the coordination

number of nitrogen from three to four when dinitrogen tetroxide forms

addition compounds as in (a) above. Since donor molecules may approach

either end of the dinitrogen tetroxide molecule, it is a simple matter

for two donor molecules to unite with one molecule of dinitrogen










3

tetroxide when the addition compound contains dinitrogen tetroxide in

molecular form. It is to be expected, then, that addition compounds

in which the undissociated molecule of dinitrogen tetroxide functions

as a Lewis acid will usually show a ratio of two moles of Lewis base

to one mole of dinitrogen tetroxide.

If, however, dinitrogen tetroxide first ionizes before accepting

electrons, as in (b) above, the situation is altered. Since only the

NO+ ion can accept electron pairs from Lewis bases, steric considera-

tions strongly suggest that a 1:1 mole ratio for addition compounds

should lead to greater stability than a ratio of two moles of Lewis

base per mole of dinitrogen tetroxide. Likewise, electronic considera-

tions indicate much greater stability for a 1:1 mole ratio. Thus it

is to be expected that addition compounds in which dinitrogen tetroxide

functions as a Lewis acid after first dissociating into NO+ and NO 3

ions will usually show a mole ratio of 1:1.

In an effort to elucidate further the formation of addition

compounds of dinitrogen tetroxide with Lewis bases, the present work

was undertaken. The addition compounds of ethers, amines, and some

aromatic electron donor systems having been fairly well investigated,

it was decided to extend the investigation to some aliphatic and

alicyclic sulfides.

The choice of the sulfides was made for several reasons:

first, the ether complexes had been characterized, and it was desirable

to compare them with the addition compounds where the next member of











4

the oxygen family acts as the donor atom; second, the influence of the

relatively large size of the sulfur atom was of interest; and third,

information was sought concerning the mode of reaction, whether com-

pound formation would occur as in (a) above or by an ionic mechanism

such as (b) above. There were strong indications from previous work

that some type of compound was formed between aliphatic sulfides and

dinitrogen tetroxide.

It was indeed found that some sulfides do form addition

compounds with dinitrogen tetroxide. These sulfide addition compounds,

though relatively stable solids at low temperatures, oxidize immediately

upon melting, thus making impossible the construction of phase diagrams.

The method of study involved measurement of the change in dielectric

constant in chloroform when solutions of dinitrogen tetroxide and the

various sulfides were mixed in varying molar proportions. Dielectric

constant measurements were used because they are easily made on

systems at low temperatures and because they give an insight into the

electrical properties of the systems.















HISTORICAL REVIEW


Physical Properties of Dinitrogen Tetroxide. Dinitrogen

tetroxide freezes at -11.5$, and boils at 21.20. It has a specific

conductivity of 1.3 x 10-12 ohm-lcm-1 at 17 (3), a dielectric con-

stant of 2.42 at 180, which shows little variation with temperature

(4), and a dipole moment equal to or nearly equal to zero for both
liquid and gaseous phases (5).

Addition Compounds of Dinitrogen Tetroxide with Ethers.

Addition compounds between dinitrogen tetroxide and the following

ethers have been studied by construction of phase diagrams: ethyl

ether, tetrahydrofuran, tetrahydropyran, l,4-dioxane, 3- /-dichloro-

ethyl ether (6), n-propyl ether, isopropyl ether, n-butyl ether, t-

butyl ether, ethylene glycol ethyl ether, 1,3-dioxane, trioxane,

perfluorotetrahydrofuran, a-methyltetrahydrofuran (7), trimethylene

oxide, 2,5-dimethyltetrahydrofuran, and 1,3-dioxolane (8). Most of

these molecules give addition compounds with a 2:1 mole ratio of

ether to dinitrogen tetroxide. A few, particularly some cyclic

ethers, are capable of forming 1:1 addition compounds. The system

1,3-dioxolane-dinitrogen tetroxide shows a mole ratio of two moles

of ether to three moles of dinitrogen tetroxide.
-('-dichloroethyl ether, perfluorotetrahydrofuran, and

5










6

t-butyl ether do not form addition compounds with dinitrogen tetroxide.

The presence of the highly electronegative groups on the former two

molecules apparently decreases the basic strength of the oxygen atom

so that no electron donation can occur. The failure of the latter

molecule to form an addition compound is presumably caused by steric

hindrance.

The usual stoichiometry of the ether addition compounds is

2:1 for ether to dinitrogen tetroxide. The compounds are white solids.

Magnetic susceptibility data show the addition compounds to be

diamagnetic. The absence of nitrogen dioxide radicals is clearly

indicated since nitrogen dioxide radicals are brown in color and are

paramagnetic. The characteristics of the ultra-violet spectra of

these compounds show that ionic species like NO+, NO3-, NO2+, or NO2-

are absent. These facts indicate strongly that the addition compounds

are of the molecular type. That is, dinitrogen tetroxide apparently

functions as a Lewis acid while retaining its molecular identity (2).

Dinitrogen tetroxide and l,U-dioxane form an addition compound

where they are in a mole ratio of 1:1. This compound has a melting

point of 450, which is far above the melting points of any of the

other ether-dinitrogen tetroxide addition compounds. The reason for

this unusual stability lies in the fact that a small activation

energy suffices to convert l,l-dioxane from its more usual "chair"

form to the "boat" form. In the "boat" form, the two oxygen atoms

approach each other closely enough to donate electrons to both nitrogen










7

atoms in a single molecule of dinitrogen tetroxide. A cyclic structure

results which accounts for the 1:1 stoichiometry. The compactness of

the structure apparently allows favorable packing in the crystal

lattice and leads to the relatively high melting point. With 1,3-

dioxane this same phenomenon is observed, though the steric factors

are not as favorable as with l,4-dioxane. The melting point of the

1,3-dioxane addition compound is 20, which is still far above most

of the ether-dinitrogen tetroxide addition compounds. The fact that

tetrahydrofuran and trimethylene oxide can also form 1:1 addition

compounds remains unexplained. These molecules have but one basic

center, so that no cyclization can occur as with the dioxanes. The

explanation for the 2:3 mole ratio of 1,3-dioxolane to dinitrogen

tetroxide is not known.


Addition Compounds of Dinitrogen Tetroxide with Amines.

Addition compounds between dinitrogen tetroxide and the following

tertiary amines have been studied: pyridine, quinoline, isoquinoline,

ao-picoline, r-picoline, acridine, 2,6-1utidine, 2-methylquinoline

(9), triethylamine (9), (10), trimethylamine, dimethylmesidine,

dimethylaniline, and N-methyldiphenylamine (10). These compounds are

yellow or red crystalline solids at low temperatures and are analogous

to complexes with nitrosyl chloride, with respect to ultra-violet

spectra. Since such addition compounds with nitrosyl chloride increase

the conductivity of solvents in which they are dissolved (10), (11),

it is felt that they are ionic. By analogy, it is assumed that such










8

complexes of dinitrogen tetroxide are also ionic. In support of this

idea is the fact that the solid complexes of dinitrogen tetroxide have

very low solubilities in ethers and hydrocarbons, but are more soluble

in more polar solvents like chlorinated hydrocarbons. If dinitrogen

tetroxide does dissociate into NO+ and NO3- ions, it would be reasonable

to expect 1:1 addition compounds to predominate. It is found that the

1i1 type addition compound is usually formed for tertiary amines and

dinitrogen tetroxide, though a 2:1 mole ratio of amine to dinitrogen

tetroxide is also sometimes formed with heterocyclic amines. Pyridine

gave a mole ratio of 2:3 for pyridine to dinitrogen tetroxide, as well

as the more usual ratios of 1:1 and 2:1.

It has been suggested that addition compounds with strong

electron donors such as the aliphatic tertiary amines exist as ionic

compounds in both the solid and liquid state, whereas the weaker

electron-donating heterocyclic amines give molecular compounds in the

solid state, but undergo dissociation to some extent to give some of

the ionic type compound in solution (12). Sterically hindered 2,6-

lutidine and 2-methylquinoline give no compounds with dinitrogen

tetroxide. When a great excess of dinitrogen tetroxide is added to

aliphatic tertiary amines, unstable solid compounds result which

contain very high mole ratios oi dinitrogen tetroxide to amine.


Compounds with Other Oxygen-Containing Lewis Bases. Other

oxygen-containing Lewis bases which have been studied include the

following: dimethyl nitrosamine, diethyl nitrosamine, methyl phenyl










9
nitrosamine, ethyl phenyl nitrosamine, pentamethylene nitrosamine,

methyl phenyl ketone, acetic acid, ethyl benzoate, acetone, benzal-

dehyde (12), ethyl acetate, benzophenone, and acetic anhydride (13).

All give addition compounds with a mole ratio of Lewis base to

dinitrogen tetroxide of 2:1, except benzophenone and acetic anhydride

which also give 1:1 addition compounds, benzaldehyde, which gives

only a 1:1 compound, and pentamethylene nitrosamine which gives 1:1

and 3:1 compounds, but no 2:1 compound. The usual mole ratio of 2:1

of nitrosamine to dinitrogen tetroxide indicates that in the solid

phase at least, these compounds are perhaps molecular in character.

However, solutions of diethyl nitrosamine in liquid dinitrogen tetroxide

of the 2:1 ratio at 00 have a specific conductivity of 3.5 x 10"- ohm-1

cm-1 (14), indicating considerable ionic dissociation of the nitrosanine

addition compounds in solution, at this temperature.

The appearance of 1:1 addition compounds with benzophenone

and benzaldehyde, both of which would have only small donating power

through the oxygen atoms, can be explained on the basis of the fact

that orbital of the aromtic rings overlap with vacant p orbitals

on the nitrogen atoms in dinitrogen tetroxide. Support is given this

idea by the fact that 1:1 compounds are formed between dinitrogen

tetroxide and the following aromatic compounds: benzene, toluene,

mesitylene, tetrahydronaphthalene, phenyl cyanide, benzyl cyanide,

nitrobenzene (12), and p-tolyl cyanide (13). Most of these addition

compounds are either orange or red. Dinitrogen tetroxide forms no










10

solid phase compounds with p-xylene, cyclehexane, chlorobenzene, or

bromobenzene, although solutions of p-xylene in dinitrogen tetraxide

at -20o have a deep red-brown color (12).

Acetonitrile and (-chloropropionitrile give solid phase

compounds with dinitrogen tetroxide of the 2:1 type, though a 1:1

compound is also formed with acetonitrile (12).


Structures of the Dinitrogen Tetracide Addition Compounds.

Nitrosyl chloride usually functions as a Lewis acid after dissociation

into NO+ and Cl" ions. The NO+ ion can accept electrons from Lewis

bases. Nitrosyl chloride does not form solid phase compounds with

benzene, 1,4-dioxane, phenyl cyanide, or pyridine (12). This fact

lends support to the belief that the addition compounds which dinitrogen

tetroxide does form with these substances are primarily molecular

rather than ionic.

The melting points of the various addition compounds correlate

approximately with the proposed structure type. Ionic type addition

compounds have higher melting points than molecular types although

the melting points of both types, as a rule, are somewhat below 0o.

The most notable exception to this generality is the very stable

cyclic 1,l-dioxane-dinitrogen tetroxide molecular type addition compound.

In light of all the evidence concerning the above dinitrogen

tetroxide addition compounds, it is reasonable to assume that in solu-

tion, the following equilibria exist:










11

(BnNO+)(N3") nB + N20 N204OnB

In the case of the strongest donors, such as aliphatic tertiary

amines, the equilibrium is shifted considerably to the ionic side,

even in the solid state. With somewhat weaker doners, like nitros-

amines or heterocyclic amines, the solid compounds are predominately

molecular. In solution, however, some ionic dissociation probably

occurs. With the weak donors, like the ethers or aromatic hydrocarbons,

the equilibrium probably lies almost totally to the right, both in

solution and in the solid state.


Classification of Addition Compounds of Dinitrogen Tetroxide

with Electron Donors. Donor molecules with their unshared pairs of

electrons in an s or 2 orbital, or some hybrid of these, have been

called "onium donors," while donors with available electrons in a

molecular orbital have been called "Tr donors." There arise four

possible general classifications for the dinitrogen tetroxide addition

compounds on the basis of the type of donor molecule: (a) molecular

compounds with "onium donors," like the ethers; (b) ionic compounds

with "onium donors," like the tertiary amines; (c) molecular compounds

with t" T donors," like the aromatic hydrocarbons; (d) ionic compounds

with Tr donors," of which type none have been observed (12), (2).

There are, of course, overlapping cases such as the heterocyclic amines,

which are intermediate between types (a) and (b) in solution, but shift

to type (a) to a large extent in the solid phase.









12

Prior Work with Dinitrogen Tetroxide and Sulfur-Containing

Lewis Bases. The first work with aliphatic sulfides and dinitrogen

tetroxide was reported by Addison and Sheldon in 1956 (15). These

workers found that dinitrogen tetroxide and aliphatic sulfides give

red solids at temperatures near -70, but that the red solids melt

with immediate oxidation-reduction a little above this temperature.

The product of the oxidation was found to be the corresponding sulfoxide,

in almost quantitative yield. None of the corresponding sulfones

were found as products. This fact suggests that dinitrogen tetroxide

and the aliphatic sulfoxides form stable compounds which inhibit further

oxidation of the sulfur. Indeed, it was found that dimethyl sulfoxide,

diethyl sulfoxide, and di-n-propyl sulfoxide all give solid compounds

with dinitrogen tetroxide, which have a 1:1 stoichiometry. Di-iso-

propyl sulfoxide and dinitrogen tetroxide give a 2:1 compound as well

as a 1:1 compound. All of these addition compounds are fairly stable,

with melting points of 380, 14, and 200 for the former compounds,

respectively, while that for the 2:1 di-isopropyl sulfoxide-dinitrogen

tetroxide compound is -3o and that for the 1:1 compound, -100

Addison and Sheldon further found that diethyl sulfone gives

no compound with dinitrogen tetroxide. The conclusion they drew is

that electron donation occurs primarily from the sulfur atom rather

than from the sulfoxide oxygen atom. The compounds were formulated

as molecular in character; the 1:1 stoichiometry is explained on the

basis of sulfoxide oxygen participation with the other nitrogen atom.












++
R2S -0

/4 Z,-0
-o

The existence of a 2:1 compound with di-isopropyl sulfoxide

may be caused by steric factors which place the sulfoxide oxygen atom

at too great a distance from the nitrogen atom for interaction. If

such is the case, the second nitrogen atom would then be free to accept

a pair of electrons from the sulfur atom of another sulfoxide molecule.


Job's Method of Continuous Variations. If some physical property

which is specific to an addition compound is measured as a function of

the mole ratio of the components of that compound, keeping total

moles of components constant, it is easily showr'that a maximum or a

minimum in the property should result when the mole ratio of the

components corresponds to that of the compound. The usefulness of this

fact was first realized by P. Job (16), and the method is now usually

referred to as "Job's method of continuous variations." Any convenient

physical property may be used, but it should be specific to the com-

pound under study, or at least the contribution to the property by

the individual components must be known. Spectrophotometric studies

(17), (18), (19) are usually used in "Job's method," but other properties

have also been used, for example, conductance (20).

When spectrophotometric analysis is employed, the usual pro-

cedure is to pick a suitable wavelength and measure optical density

1See Appendix I.










1l

as a function of mole ratio of components, keeping the total number

of moles constant. The difference between the observed optical density

and the sum of the optical densities of the individual components

in solution, had there been no interaction, is calculated. This

difference is then plotted as a function of the mole ratio of the

components, and a maximum indicates a compound of the formula in-

dicated by the mole ratio of components at that point.

There are complications when more than one compound is formed.

It has been shown (21) that when two compounds are formed, the physical

property first reaches a maximum at a mole ratio which is below the

actual mole ratio of the first compound, while the physical property

reaches a second maximum at a mole ratio which is above the actual

mole ratio of the second compound. The displacements are usually

small, however, and introduce little error if the mole ratios of the

two compounds are not close to each other.

Dielectric constant measurements have been used to study the

formation of molecular addition compounds. For example, McCusker,

et al. (22), (23), (2) measured the dielectric constants of solutions

of various inorganic halides in dioxane. They did not, however, use

the variations method in interpreting their results. Apparently,

dielectric constant has not previously been used as the physical

property for a variations study.

















EXPERIMENTAL PROCEDURES


Methods of Analysis of Sulfide-Dinitrogen Tetroxide Systems.

The primary method of analysis of the aliphatic and alicyclic sulfide-

dinitrogen tetroxide systems employed in this work was that of "Job's

method of continuous variations" using dielectric constant as the

physical property measured. Chloroform was used as the solvent. A

few ether-dinitrogen tetroxide systems in chloroform were also studied

using this method.

Cryoscopic measurements were made on two of the more stable

sulfide addition compounds in chloroform solutions in order to get a

measure of the degree of dissociation of the compounds.

Solubilities of the addition compounds in several solvents

besides chloroform were determined.

Finally, the oxidation of dithiane and trithiane by dinitrogen

tetroxide was investigated.

Purification of Materials. Dinitrogen tetrexide was prepared

by condensation of commercial nitrogen dioxide. Traces of nitric

oxide are usually present in commercial nitrogen dioxide. Nitric

oxide combines with nitrogen dioxide to form dinitrogen trioxide,

which is deep blue in color in the liquid or solid state (B. P. 50).

The presence of an impurity from this source in nitrogen dioxide is

15










16

thus easily detected by condensing the nitrogen dioxide to liquid or

solid dinitrogen tetroxide. Any blue or greenish-blue coloration

indicates the presence of dinitrogen trioxide. At first, the dinitro-

gen trioxide was converted into dinitrogen tetroxide by bubbling oxygen

gas through the impure dinitrogen tetroxide at 0 until the greenish

solution became brown. However, it was later found that the traces

of nitric oxide could be removed by passing the gas at a moderate

rate from the cylinder directly through a short glass tube (10 cm.

leng and 1.5 cm. in diameter) filled with phosphorus (V) oxide and

sand. The nitrogen dioxide was condensed to snow white solid

dinitrogen tetroxide in a glass trap cooled by a chloroform-carbon

tetrachloride-dry ice mixture. Freezing point measurements indicated

that the dinitrogen tetroxide obtained from this treatment was quite

pure. Exactly how the purification was effected by the phosphorus (V)

oxide and sand is unexplained. Complete drying of the dinitrogen

tetraxide was obtained by warming the trap to room temperature and

slowly distilling the dinitrogen tetrsxide through a longer glass tube

(40 cm. long and 2 cm. in diameter) filled with phosphorus (V) oxide

and sand into a transfer cell (Fig. 1) cooled by the dry ice mixture.

The transfer cell was kept in a refrigerator at about 50 until the

dinitrogen tetroxide was needed. The pure dinitrogen tetroxide could

be conveniently stored for several months in this manner. Gl ss

apparatus was used as far as possible in handling the dinitrogen

tetroxide, but some connections were made with thin-walled Teflon
















































Fig. 1 120L Transfer Cell










18

tubing. The Teflon showed no signs of decomposition after two -ears

of use.

The aliphatic sulfides investigated in this work were:

bis-(chloromethyl) sulfide, dimethyl sulfide, diethyl sulfide, di-n-

propyl sulfide, di-n-butyl sulfide, and di-isoamyl sulfide. The

alicyclic sulfides studied were l,-dithiane and trithiane. The

following ethers were also investigated: l,h-dioxane, n-butyl ether,

and tetrahydropyran. All of these substances with the exception of

dithiane were obtained fro- commercial sources. The liquids were

dried and distilled; the constant boiling middle cut was retained.

A list of the compounds obtained coamercially is found in Table 1.

Dithiane was synthesized by a method similar to one reported

in the literature by lesson (25), in which dithiane is prepared by the

reaction of potassium sulfide with ethylene dibromide in alcohol

solution. A mixture of 600 ml. of 95 per cent ethanol and 250 .. of

potassium hydroxide was saturated with hydrogen sulfide as-. This

mixture was then placed in a large round bottom flask fitted with

dro jis.o fu.iel, stirrer, and reflux condenser. -ith rail stirring,

282 g. of ethylene dibromide was added dropwise at a rate E -icic..t

to maintain gentle reflux, the heat of reaction being sufficient to

accomplish this. After all the ethylene dibromide had been added,

the mixture was warmed to maintain a gentle reflux for two more hours.

At the end of that time, the mixture, which was a white paste, was

steam distilled. About 500 ml. of a clear, colorless alcoholic














TABLE 1
COMPOUNDS OBTAINED COI1ERCIALLY


Substance Source* Drying Agent B.P. of cut Lit. B.P.
(uncorr.)

C1CH2SCH2C1 S Antyd. CaC12 156-70 1560

CH3SCH3 CZ Na 37.20 37.1-.20

C2H5SC2H5 D Aniyd. CaC12 90.3 92.10

C3H SC 3H E Na 140-10 142-3

C4H9SC4H9 E Anhyd. CaC12 185-6 182

C5H1SCJ5H1 E Anbyd. CaC12 216-70 2160
SCH2SCH2SCH2 E (M.P. 216-80) (M.P. 2160)
L I
OCH2CH20CH2CH2 C Na 101 101.4

C4H90OCH9 C Na 1400 142.h-
OCH2CH2CH2CH2CH2 EN Na 87.5-.60 88
I I


- Stauffer Chemical Co.

- Crown Zellerbach Corporation

- Eastman Chemicals

- Carbide and Carbon Chemicals Co.

- Eastern Chemical Co.










20

forerun was obtained. It was diluted to two liters with water and

placed in a refrigerator. Solid dithiane crystallized in a short time.

Continued steam distillation of the reaction mixture carried over

solid dithiane. The total amount of dithiane produced was about 18.g.

The yield was only 20 per cent, but the product was of high purity.

One recrystallization from 95 per cent ethanol produced a snow white,

almost odorless product. M. P. 111.2-112.0, Lit. 111-12.

Chloroform of U.S.P. grade was obtained from Fisher Chemical

Company. It was allowed to stand for at least a week over anhydrous

calcium chloride. Following this treatment, it was fractionated in

a 121 cm. heated column, packed with gles helices, at a reflux ratio

of about 50l1. The alcohol azeotrope distilled at 590. When the head

temperature became 610, the reflux ratio was decreased and the chloro-

form collected. The 610 fraction was immediately fractionated in an

87 cm. heated column, pRtked with small saddles, at a reflux ratio

of about 5 1. After removal of a small forerun, chloroform boiling

at 61.2-.30 was collected. The literature value is 61.20. Since

chloroform which has had the alcohol removed is susceptible to oxida-

tion, the fractionations were carried out immediately prior to using

the chloroform.


Dielectric Constant Measurements. The dielectric constants

of the various solutions of the addition compounds were measured by

the heterodyne beat method. The instrument used consists essentially

of a fixed quartz crystal oscillator operating at 250 kilocycles in









21

conjunction with a vacuum tube oscillator of variable frequency con-

trolled by the adjustment of a precision condenser. The resistance

and inductance remain substantially constant. A one kilocycle tuning

fork is beat against the difference between the fixed and variable

oscillators. An oscilloscope was used so that visual as well as

audible means were employed to determine when the constant difference

of one kilocycle obtained between the quartz and variable oscillators.

After such balance of the system was obtained without the measuring

cell containing the solution under study, the cell was connected in

parallel with the precision condenser and balance then re-established

by manipulation of the precision condenser. The difference in

capacitance to the nearest tenth of a micro-micro farad between the

balanced system without the measuring cell and the balanced system

with the measuring cell was read directly from the precision condenser.

This difference gave the capacitance of the measuring cell. The

dielectric constants of the solutions were calculated by dividing the

capacitance of the measuring cell with the particular solution as the

dielectric by the capacitance of the cell with dry air between the

plates (26).

The measuring cell (Fig. 2) used in these studies was obtained

from J. C. Balsbaugh, Marshfield Hills, Massachusetts, type 2TN50.

It was constructed of pyrex type glass. The capacitance of the glass

and wire leads was obtained by measuring the dielectric constant of

a constant boiling fraction of Eastman spectral grade iso-octane, at








22












-600. A temperature correction to the dielectric constant of iso-

octane was applied by the relations

Et 1.940 0.00142(t 20) (27)

The temperature of the measuring cell was controlled by means

of a Dewar flask fitted with a calibrated toluene-in-ga ss ther-

mometer (Fig. 3). A chloroform and carbon tetrachloride solution was

cooled to the temperature at which the measurements were to be taken

and small pieces of dry ice added from time to time as necessary to

maintain the low temperature. Most of the measurements were made at

-600.

Standard solutions of dinitrogen tetroxide in chloroform were

prepared using an all glass apparatus (Fig. W). Receiver A was filled

with approximately 15 ml. of chloroform. With ball joint B sealed,

the entire receiver was weighed to the nearest milligram. The female

bridge was then attached to ball joint B so as to connect the dinitro-

gen tetroxide transfer cell. With stopcock C open and stopcock D

closed, receiver A was cooled to -$50 to -600. Stopcock D was then

opened and dinitrogen tetroxide allowed to distill into receiver A.

The rate of distillation could be controlled by regulating the height

of the cooling bath and warming the dinitrogen tetroxide transfer

cell with the hand. From time to time, stopcocks C and D were closed

and the transfer cell was removed and weighed in order to get an

approximate measure of the dinitrogen tetroxide which had distilled.

When the desired amount, plus a small excess, had distilled, the




















Opening for
iMeasuring Cell


Opening for
Thermometer


Openings for
Dry Ice


----


Fig. 3 Top of Dewar Flask



























f+-4
0

o ol
0
P4 0










0 C
o




Ca-

















O
O O

I











26

cooling bath was removed, stopcock D closed, and the transfer cell

removed. As the receiver A warmed to room temperature, some of the

dinitrogen tetroxide would unavoidably be lost by volitilization.

From experience, this loss could be estimated and the necessary excess

added as mentioned. After the receiver A had warned to room tempera-

ture, ball joint B was again sealed and the receiver weighed to the

nearest milligram. By difference, the weight of dinitrogen tetroxide

added to the chloroform was obtained. Cap E was then removed and the

standard taper male joint inserted into a volumetric flask containing

about 50 ml. of chloroform. By careful pouring, the dinitrogen

tetroxide-chloroform solution in receiver A was transferred to the

volumetric flask. The receiver was rinsed several times with chloro-

form and these washings added to the volumetric flask. The volumetric

flask was then diluted to the mark with chloroform, at room temperature.

The standard sulfide and ether solutions in chloroform were prepared

by directly weighing the components of the solutions.

The concentrations of solutions employed were about 0.05 -

0.06M since, at such sall concentrations, the dielectric constant

of the separate dinitrogen tetroxide and sulfide and ether solutions

at -60o was essentially that of pure chloroform at -600. Also, at

these concentrations, loss by evaporation of dinitrogen tetroxide is

slight and was shown to introduce only small error.2


2See Appendix II.










27

Provided volumes are additive, the varying of mole ratios of

the components of a compound, as required in the method of continuous

variation, may be accomplished by varying the relative volumes of

solutions which contain each of the components at equal concentrations

while always holding the total volume constant (16), (28). This method

was employed since volumes certainly are substantially additive at a

concentration of 0.06M.

Total volume in the cell was held at 50 ml., measured at room

temperature. At -60, the volume was approximately 45 ml. The observed

volume contraction is in good agreement with the expected contraction

for pure chloroform at the same temperature, which reinforces the

assumption of additivity of volumes. A typical experiment was carried

out as follows: 20 ml. of a 0.06M solution of the sulfide was

pipetted into the glass measuring cell, and the cell was then fitted

with a drying tube filled with phosphorus (V) oxide and sand. Next,

30 al. of a 0.06M solution of dinitrogen tetroxide was pipetted into

a cylinder bent at the top and equipped with a male joint which would

fit into the dielectric constant measuring cell. This cylinder was

likewise fitted with a drying tube filled with phosphorus (V) oxide

and sand. Both the mBasuring cell and the cylinder were then immersed

in a cooling bath at -78 for about two minutes. At the end of this

time, the drying tubes were removed, the cylinder was fitted into the

measuring cell, and the cooled solutions were mixed. The cell, with

the cylinder still attached, was then returned to the cooling bath










28

for a little longer and shaken occasionally to insure thorough mixing.

In the case of the sulfide-dinitrogen tetroxide systems, the colorless

solutions of the two components form a red solution upon mixing.

Finally, the measuring cell, with the cylinder, was placed in the Dewar

flask containing chloroform and the carbon tetrachloride at the tempera-

ture at which the measurement was to be made. The cylinder was then

removed and the nickel condenser fitted into the measuring cell. The

system was alleged to stand twenty minutes to establish temperature

equilibrium. Small pieces of dry ice were added to the Dewar flask

as necessary. At the end of twenty minutes, the capacitance of the

cell was measured. Determination of the temperature of the solution

in the cell immediately after taking the capacitance measurement in

every ease showed its temperature to be equal to that indicated by

the thermometer in the cooling bath of the Dewar flask. Theoretical

calculations3 also predict that temperature equilibrium was reached.

From experiments such as that just described, the dielectric constant

of a solution in which the mole ratio of sulfide to dinitrogen tetroxide

is 2:3 was obtained. The dielectric constants of solutions with other

mole ratios were obtained in the same way by using different volume

proportions; e.g., using 25 ml. of each solution would give data for

a 1:1 mole ratio.


Measurements of Freezing Point Depression. The lowering of

the freezing point of chloroform solutions of two of the more stable

3See Appendix III.










29

sulfide addition compounds was measured. Using solutions in which

the sulfide to dinitrogen tetroxide mole ratio was that as indicated

for the addition compound by the dielectric constant studies, a cal-

culation of the degree of dissociation of the addition compound was

possible. The molal freezing point depression of chloroform was

determined from solutions of known concentrations of dinitrogen

ttroxide.

A variable range, variable zero Speedomax, Type G, Leeds

and Northrup Recording Potentiometer fitted with a copper-constantan

thermocouple was used to measure temperature. The freezing point

cell (Fig. 5) was equipped with a thermocouple well filled with

iso-octane to insure good thermal contact. The solutions were stirred

constantly as the temperature was lowered in a chloroform-carbon

tetrachloride-dry ice bath. The stirring was accomplished by a glass

spiral, the top part of which was connected to a sealed glass tube

containing an iron slug. A solenoid was placed around the upper part

of the freezing point cell in such a manner that by alternate activa-

tion and deactivation, the stirrer was agitated. Alternate activation

and deactivation of the solenoid was obtained by means of a small

constant-speed motor which turned a split ring commutator on brushes

in series with a rheostat which powered the solenoid.


Attempts to Isolate Solid Complexes. Many attempts were made

to precipitate the sulfide-dinitrogen tetroxide addition compounds

out of solution. The compounds are very soluble in chloroform,

giving yellow-red to red solutions. They are also quite soluble in
























r










31

ethyl ether, giving yellowish solutions. In ether solutions, they

seem to be fairly susceptible to oxidation-reduction, the solutions

often becoming greenish in color after a few minutes, even at -78o.

The compounds are very soluble in acetone, giving colors similar to

the chloroform solutions except darker. In hexane, yellow solutions

result, though the compounds are only moderately soluble. At -78,

in hexane solutions, a tar-like substance settles out after a few hours.

The color of this tar-like substance depends upon the concentrations

of the dinitrogen tetroxide and sulfide solutions. When dilute solu-

tions are mixed, the tar is brownish green, whereas with more concen-

trated solutions, the color is red. No well-defined crystalline solid

could ever be isolated, however.

As soon as the temperature of any of these solutions is

allowed to rise much above -$0, the solutions containing aliphatic

sulfides and dinitrogen tetroxide turn green. Cooling does not re-

store the original color. If, however, trithiane or dithiane is

used as the sulfide, warming the solution, even to room temperature,

does not produce a green color, but simply the brown color of nitrogen

dioxide. Brown fumes can be seen above the solution. Upon cooling

these solutions to around -50, the original purple to red color is

restored. This reversible color change can be made to occur several

times before oxidation-reduction renders the change impossible.

Numerous attempts were made to isolate pure solid addition

compounds by adding a given sulfide to a large excess of dinitrogen










32

tetroxide at -50 to -55. The solid mixture of addition compound

and excess dinitrogen tetroxide was then subjected to reduced pressure

in an attempt to remove the excess dinitrogen tetroxide, which has a

vapor pressure in excess of one millimeter of mercury at -55. The

dry, red solids which result were hydrolyzed with a O.5M NaOH in

50 per cent ethanol solution. Total nitrogen and sulfur analyses

were obtained to determine mole ratios of addition compound con-

stituents, assuming only dinitrogen tetroxide and the particular

sulfide to be the components. No consistent results could be obtained.

Relative excesses of dinitrogen tetroxide and length of vacuum applica-

tions were varied considerably in different experiments. Apparently

the sulfide-dinitrogen tetroxide addition compounds are not stable at

pressures around one millimeter of mercury, even at -500 to -55$

Most of these experiments were carried out in a specially

designed all-glass reaction apparatus (Fig. 6).


Oxidation of Dithiane and Trithiane by Dinitrogen Tetroxide.

A large excess of dinitrogen tetroxide mas distilled directly onto

solid dithiane in the reaction apparatus. The temperature of the

mixture was brought to 00 and held for about 12 hours. At the end

of that time, the solution was blue with a white solid on the bottom

of the container. Excess dinitrogen tetroxide was removed by vacuum.

The solid residue decomposed at 225-30. After recrystallization from

95 per cent ethanol, the resulting solid decomposed at 263-5. Sub-

























































Fig. 6 Glass Reaction Apparatus











3h

limation of the solid which decomposed at 225-300, gave another -rite

solid, which, after recrystallization from 95 per cent ethanol,

melted at 205-70. It was found that addition of excess ainitrogen

tetroxide at 00 for a few hours to the solid decomposing at 263-50,

followed by removal of excess dinitrogen tetroxide, reforms the

white solid decomposing at 225-300. Lle-ientary analyses for nitro =

and sulfur were performed on these white solids. A quantitative

carbon and hydrogen determination was made on the solid neltiil at

205-70.

A similar treatment of trithiane with liquid dinitrogen

tetroxide resulted in the formation of an amorphous, yellow solid,

which was insoluble in all ordinary solvents. The substance contained

some free sulfur, but no crystallization could be induced after ex-

traction with carbon disulfide. Sublimation of the substance led to

its complete decomposition with the production of gaseous products

with foul sulfide-like odors.
















RESULTS


Dielectric Constant Measurements. Results for all systems

studied by means of measurement of their dielectric constants in

chloroform solutions are presented in tables 2 through 11. Listed

in these tables are the following: the temperature in degrees

Centigrade, T, at which the measurement was made; the molarity, M,

of both the sulfide and dinitrogen tetroxide solutions before mixing;

the color of the solution after mixing, i.e., the color of the addition

compound in solution; the volumes in milliliters of the sulfide and

dinitrogen tetroxide solutions; the mole ratio of sulfide to dinitrogen

tetroxide in the solution after mixing; and, finally, the dielectric

constant, E of the solution.

For those sulfide-dinitrogen tetroxide systems which show a

significant increase in dielectric constant over the dielectric con-

stant of chloroform, and hence are amenable to analysis by Job's

method of continuous variations, the data, for -60.00, are also

presented graphically in figures 7 through 11.

The dielectric constant of pure chloroform at -600 was found

to be 6.75.








36
TABLE 2

SYSTEM: DIMETHYL SULFIDE DINITROGEN TETROXIDE


Mls. Mls. Mole Ratio
T M Color Sulfide N204 Sulfide/N204 (
Soln. Soln.

-60.0 0.062 Pale yellow 10.0 40.0 1:I 7.04

-60.00 0.062 Light orange 15.0 35.0 1:2.3 7.13

-60.00 0.062 Light orange 20.0 30.0 1:1.5 7.20

-60.0 0.062 Light orange 25.0 25.0 1:1 7.27

-60.0 0.062 Light orange 30.0 20.0 1:0.67 7.23

-60.0O 0.062 Light orange 35.0 15.0 1:0.43 7.19

-60.00 0.062 Pale yellow 40.0 10.0 1:0.25 7.10

-56.00 0.065 Light orange 25.0 25.0 1:1 6.95
-52.0 0.065 Light orange 25.0 25.0 1:1 6.86


TABLE 3
SYSTEM: BIS-(CHLOROMETHYL) SULFIDE DINITROGEN TETROXIDE


Mis. Mis. Mole Ratio
T M Color Sulfide N204 Sulfide/N204
Soln. Soln.

-60.00 0.096 Colorless 10.0 40.0 1:4 6.76

-60.00 0.096 Colorless 20.0 30.0 1:1.5 6.75

-60.00 0.096 Colorless 25.0 25.0 1:1 6.74

-60.0 0.096 Colorless 35.0 15.0 1:o.43 6.75

















TA BLE I
SYSTEM: DIETHYL SULFIDE DINITROGEN TETROXIDE


Mis. Mis. Mole Ratio
T M Color Sulfide N204 Sulfide/N204O
Soln. Soln.

-60.00 0.060 Pale orange-red 5.0 45.0 1:9 7.24

-60.00 0.060 Orange-red 10.0 40.0 1i4 7.41
-60.00 0.060 Orange-red 12.0 38.0 1:3.2 7.43

-60.00 0.060 Orange-red 15.0 35.0 1:2.3 7.45

-60.0 0.060 Orange-red 17.0 33.0 1:1.9 7.42

-60.00 0.060 Orange-red 20.0 30.0 11.5 7.41

-60.00 0.060 Orange-red 2 5.0 25.0 1:1 ?.31

-60.0 0.060 Orange-red 30.0 20.0 1:0.67 7.31
-60.0 0.060 Pale red-orange 35.0 15.0 1:0.43 7.22



















TABLE 5

SYSTEM: DI-n-PROPYL SULFIDE DINITROGEN TETROXIDE


.s. 1is. Mole Ratio
T M Color Sulfide N204 Sulfide/N204 E
Soln. Soln.

-60.00 0.060 Orange 10.0 40.0 1:4 7.58

-60.0o 0.060 Red-orange 12.0 38.0 1:3.2 7.70

-60.00 0.060 Red-orange 15.0 35.0 1:2.3 7.77

-60.00 0.060 Red-orange 20.0 30.0 1:1.5 7.70

-60.00 0.060 Orange-red 25.0 25.0 1:1 7.68

-60.00 0.060 Orange-red 30.0 20.0 1:0.67 7.62

-60.00 0.060 Orange 35.0 15.0 1:0.h3 7.53

-60.00 0.060 Pale orange 40.O 10.0 1:0.25 7.33


















TABLE 6

SYSTEM: DI-n-BUTYL SULFIDE DINITROGEN TETROXIDE


Mis. Mls. Mole Ratio
T M Color Sulfide N204 Sulfide/N20h
Soln. Soln.

-60.00 0.05 Orange-red 15.0 35.0 1:2.3 7.56

-60.0o .0O5 Orange-red 20.0 30.0 1:1.5 7.56
-60.00 0.045 Orange-red 25.0 25.0 1:1 7.56

-60.0 0.045 Orange-red 34.O 16.0 1:0.47 7.48
-60.00 0.062 Dark orange-red 10.0 40.0 1:4 7.51

-60.00 0.062 Dark orange-red 15.0 35.0 1:2.3 7.71

-60.00 0.062 Dark orange-red 17.5 32.5 1:1.9 7.68

-60.00 0.062 Dark orange-red 20.0 30.0 1:1.5 7.72

-60.00 0.062 Dark orange-red 22.0 28.0 1:1.3 7.71
-60.0 0.062 Dark orange-red 25.0 25.0 1:1 7.65

-60.00 0.062 Orange-red 30.0 20.0 1:0.67 7.63

-60.00 0.062 Orange-red 33.0 17.0 1:0.52 7.47

-60.00 0.062 Red-orange 40.O 10.0 1:0.25 7.29

-56.0 0.065 Dark orange-red 20.0 30.0 1:1.5 7.58

-52.5 0.065 Dark orange-red 20.0 30.0 1:1.5 7.41


















TABLE 7

SYSTEM: DI-ISOAMIL SULFIDS DINITROGEN TETROXIDE


Mis. Mis. Mole Ratio
T M Color Sulfide N20g Sulfide/N204 E
Soln. Seln.

-60.00 0.060 Orange-red 5.0 45.0 1:9. 7.26

-60.00 0.060 Dark orange-red 10.0 40.0 1:4 7.40

-60.00 0.060 Dark orange-red 15.0 35.0 1:2.3 7.60

-60.00 0.060 Dark orange-red 20.0 3040 1:1.5 7.68
-60.00 0.060 Dark orange-red 25.0 25.0 1:1 7.61

-60.00 0.060 Orange-red 30.0 20.0 1:0.67 7.42

-60.00 0.060 Red-orange 35.0 15.0 1:0.43 7.27

-60.00 0.060 Red-orange 4O.0 10.0 1:0.25 7.22

-60.0 0.060 Yellow-orange 45.0 5.0 1:0.11 6.9








4l

TABLE 8

SYSTEM: 1,h-DITHIANE DINITROGEN TETROXIDE


Mis*. Ms. Mole Ratio
T M Color* Sulfide N20h Sulfide/N204
Soln. Sool

-60.00 0.046 Pale yellow 1.0 49.0 lsh9 6.84

-60.00 0.046 Pale red-orange -5.0 45.0 1:9 6.86

-60.00 0.0O6 Pale red-orange 10.0 40.0 1:4 6.82

-60.00 0.0O6 Pale red-orange 15.0 35.0 1:2.3 6.79

-60.00 0.046 Very pale orange- 25..0 25.0 1:1 6.74
yellow

-60.00 0.0h6 Very pale yellow 44.O 16.0 1:0o.1 6.69

-60.00 0.060 Very pale yellow 25.0 25.0 1:1

*There was an induction period of about a minute after mixing
the colorless solutions before the color appeared as described.


TABLE 9
SYSTEM: n-BUTYL ETHER DINITROGEN TETROXIDE


Mls. Mls. Mole Ratio
T M Color Ether N204 Ether/N204
Soln. Soln.

-60.00 0.05 Colorless 15.0 35.0 1.2.3 6.82

-60.00 0.05 Colorless 25.0 25.0 1:1 6.85

-60.00 0.05 Colorless 35.0 15.0 1:0.43 6.82








42

TABLE 10

SYSTEM: TETRAlIDROPYRAN DINITROGEN


TETROXIDE


Mls. Mls. Mole Ratio
T M Color* Ether N204 Ether/N204
Soln. Soln.

.-60.00 0.057 Colorless 10.0 40.0 l:l 6.87

-60.00 0.057 Colorless 15.0 35.0 1:2.3 6.89

-60.00 0.057 Colorless 20.0 30.0 1:1.5 6.93

-60.00 0.057 Colorless 25. 25.0 0 1:1 6.93

-60.00 0.057 Colorless 30.0 20.0 1:0.67 6.95

-60.0 0.057 Colorless 33.0 17.0 1:0.52 6.90

-60.0o 0.057 Colorless O4.O 10.0 1:0.25 6.87

-60.0o 0.057 Colorless 45.0 5.0 1:0.11 6.85

*At the end of the experiments, the solutions were very pale
blue.


TABLE 11

SYSTEM: 1,4-DIOXANE DINITROGEN TETROXIDE


Mls. Mis. Mole Ratio
T M Color* Ether N204 Ether/N204 E
Soln. Soln.

-60.0O 0.056 Colorless 20.0 30.0 1:1.5 6.70

-60.00 0.056 Colorless 25.0 25.0 1:1 6.69

-60.00 0.056 Colorless 30.0 20.0 1:0.67 6.72

-At the end of the experiments, the solutions were extremely
pale blue.


















7.75




7.25


10.0


20.0


30.0


40.0


Mls. 0.062i Dimethyl sulfide

Fig. 7 Dimethyl Sulfide-Dinitrogen Tetroxide


7.75 -


7.25- e e



I --
10.0 20.0 30.0 40.0
iHs. 0.060M Diethyl sulfide
Fig. 8 Diethyl Sulfide-Dinitrogen Tetroxide


I I -0


__


*T .-. -- - -
















7.75

C


10.0 20.0 30.0 40.0
Nis. 0.0601G Di-n-propyl sulfide
Fig. 9 Di-n-propyl Sulfide-Dinitrogen Tetroxide


4



/

/


IIL~




0U


10.0 20.0 30.0 14.0.0
Mis. 0.0621, Di-n-butyl sulfide
Fig. 10 Di-n-butyl Sulfide-Dinitrogen Tetroxide


7.25


__ _

















7.75




7.25


10.0 20.0 30.0 40.0
His. 0.060M Di-isoamyl sulfide
Fig. 11 Di-isoanyl Sulfido-Dinitrogen Tetroxide










46

Measurements of Freezing Point o ression. The results of

the measurements of freezing point depressions on the s Ft .. di-n-

butyl sulfide-dinitrogen tetroxide and di-isoamyl sulfide-dinitro :en

tetroxide are presented in Table 12.

~he molal freezing point depression constant, Kf, was deter-

mined using a 0.029m :3'oL-in-chloroform solution. A depression of

1.hl was noted for this solution, which, when substituted into the

relation:

ST = Kf*m

gives a value for .' of h8.6. Usii this value and the measured

freezing point depression, AT, for these solutions, the molality,

m, of total species in solution was calculated. The solutions on

which the measure ents were made contained the sulfide and dinitro en

tetroxide in the mole ratio corresponding to the mole ratio at the

maximum in their dielectric constant curves, viz., a ratio of sulfide

to dinitrogen tetroxide of 2:3. With the assumption that the 1..I

species in these solutions are the addition compounds and uncombined

sulfide and dinitrogen tetroxide molecules, the degree of dissociation,

o was calculated and is included in the results.

TALkT 12


System AT m <

Di-n-butyl sulfide-dinitrogen tetroxide 1.h7 0.030 0.

Di-isoamryl sulfide-dinitrogen tetroxide 1.25 0.026 0.h7












Oxidation of Dithiane with Dinitrogen Tetroxide. The reaction

between 1,4-dithiane and dinitrogen tetroxide gave a solid product,

which decomposed at 225-300, and was found to contain sulfur and nitro-

gen. After recrystallization, the white solid decomposed at 263-S0,

and was found to contain sulfur, but no nitrogen. This latter product

was identified by its decomposition point and crystal structure (29)

as mostly dithiane c<-disulfoxide (trans form) and a small amount of

dithiane -disulfoxide (cis form)*4 Addition of dinitrogen tetroxide

to some of the dithiane o(-disulfoxide again gave the substance de-

composing at 225-30. This product is absolutely white at room

temperature and has little or no odor. It is apparently an addition


Sincere appreciation is expressed to Miss Geraldine Westmoreland
for her detailed study of the oxidation of dithiane by dinitrogen
tetroxide in chloroform solution to give a mixture of the e<- and -
disulfoxides of dithiane. Her study included a comparison between
this method of preparation and the older method using hydrogen peroxide
(29). It was her conclusion that the oxidation of dithiane to the
disulfoxides of the dinitrogen tetroxide method is superior to that
of the hydrogen peroxide method for the following reasons: (a)
dinitrogen tetroxide produces only the disulfoxides in 100 per cent
yield, whereas a slight excess of hydrogen peroxide is likely to
cause further oxidation of the disulfoxides to the trioxide or
disulfone; (b) the dinitrogen tetroxide method is less time consuming,
requiring at most 12 hours, whereas the hydrogen peroxide method
requires about two days; (c) the laboratory manipulations are simpler
using dinitrogen tetroxide, since, if commercial dinitrogen tet-
roxide is used, the only laboratory operation beyond the very simplest
is the removal of excess dinitrogen tetroxide with a water pump at
the end of the experiment; use of hydrogen peroxide requires repeated
steam distillations and evaporation of aqueous solutions to dryness.
Both methods produce predominately the ao- or trans-
disulfoxide and relatively little of the or cis-disulfoxide.








48

compound of dithiane o<-disulfoxide and dinitrogen tetroxide, though
a few quantitative determinations failed to show a definite mole

ratio of sulfur to nitrogen. However, the ratio of sulfur to nitrogen

was always high.
Tne white solid obtained from the sublimation of the dithiane
o<-disulfoxide-dinitrogen tetroxide addition compound contained sulfur,

but no nitrogen. This compound was identified by its melting point
of 205-70 to be dithiane monosulfone. The melting point of this
compound has been reported variously in the literature as 2000 (30),

and 2030 (31). Calculated for CHH8S202: C, 31.6 per cent; H, 5.2

per cent; found: C, 31.7 per cent; H, 5.4 per cnt.5

These results may be summarized as follows:


,CH2-CHI2\S

Sublime __ S S
i 0/150 190 > GCH2*CH2/ 0




20N204
/CH2-CH2 / CH2*CH2\ Recryst, from
S S *N20 + S S *1204 95$ htoH
- 'CH2*CH2 0 n CHI2CH / 0 n 4


/CH2OCH2 0\ CH2CH2\
S C + \
0/ CH2.CH2/ 0 CHI{2.CH2 \0


5Analyses performed by Galbraith Microanalytical Laboratories,
Knoxville, Tennessee.










49

Mixing dinitrogen tetraxide with dithiane disulfone, under

conditions similar to those for the reaction between dinitrogen

tetroxide and dithiane o(-disulfoxide, gave no reaction. The dithiane

disulfone was recovered unchanged in 100 per cent yield.
















DISCUSSION


Type of Addition Compound Formed Between the Sulfides and

Dinitrogen Tetroxide. Addition compounds of dinitrogen tetrcxide

usually contain the dinitrogen tetroxide either in an essentially

molecular form or in an essentially ionic form. We mut consider

which form is the more likely for the case of the sulfide-dinitrogen

tetrocide addition compounds.

The donor atom in the sulfide Lewis bases is, of course, the

sulfur atom. Since sulfur is a member of the oxygen family, it cou3d

perhaps be inferred that addition compounds of dinitrogen tetroxide

involving sulfur as the donor atom should resemble addition compounds

of dinitrogen tetroxide involving oxygen as the donor atom. From such

an analogy, it would be concluded that the sulfide-dinitrogen tetroxide

addition compounds contain dinitrogen tetroxide in the form of un-

dissociated molecules. On the other hand, the sulfur atom is much

larger than the oxygen atom. Mainly because of this size difference,

the unshared electrons of sulfur are less strongly attracted by its

nucleus than are the unshared electrons of oxygen. Consequently,

sulfur should be a stronger electron donor than is oxygen. On this

basis, it could be argued that the sulfides may be strong enough Lewis

bases to lead to the dissociation of dinitrogen tetroxide into some

50










51

ionic species. It thus becomes evident that an attempt to predict

the nature of the sulfide-dinitrogen tetroxide addition compounds

by analogy with previously studied addition compounds of dinitrogen

tetroxide is of little value.

Experimental evidence strongly suggests that the solid sulfide-

dinitrogen tetroxide addition compounds are unstable under reduced

pressures even at low temperature. If the sulfides are strong enough

Lewis bases to lead to the dissociation of dinitrogen tetroxide into

ions, it mould be reasonable to expect that the resulting addition

compounds would, under reduced pressure, be stable with respect to

dissociation into free acid and base. Thus, amines form addition

compounds with dinitrogen tetroxide which are stable with respect to

dissociation into free acid and base at quite low pressures, provided

the temperature is low. Some of the heterocyclic amine-dinitrogen

tetroxide addition compounds are thought to contain undissociated

dinitrogen tetroxide in the solid state (12), dissociation occurring

only in solution. It would seem unreasonable to think that the sulfide

bases should be stronger electron donors than the heterocyclic amine

bases and yet form addition compounds with dinitrogen tetroxide which

show less stability under reduced pressure than the heterocyclic

amine-dinitrogen tetroxide addition compounds. If, then, the sulfide

bases are no stronger, and are probably even weaker, electron donors

than the heterocyclic amine bases, it is reasonable to assume that in

the solid state, the dinitrogen tetroxide in the sulfide-dinitrogen











52

tetroxide addition compounds is not dissociated into ions.

However, we must consider the possibility that even tloou h

the solid sulfide-dinitrogen tetroxide addition compounds contain

molecular dinitrogen tetroxide, some dissociation into ions could occur

in solution. The heterocyclic amine-dinitrogen tetroxide addition

compounds are, as a rule, only sparingly soluble in ethyl ether.

The sulfide-dinitrogen tetroxide addition compounds, however, are all

soluble in ethyl ether, and, as a matter of fact, are apparently

somewhat soluble in hexane. At least, they are very difficult to

precipitate from this solvent. This evidence suggests that ionic

species are not present to the significant extent in solutions of

sulfide-dinitrogen tetroxide addition compounds.

One further possibility which must be considered is that in

chloroform solutions, dissociation of the dinitrogen tetroxide into

ions may occur. It is a fact that predominately ionic addition com-

pounds of dinitrogen tetroxide with aliphatic amines show increased

solubility in chloroform and other chlorinated i. irocar.ons as compared

with less polar solvents. It could be argued from this fact that perhaps

chloroform is polar enough to cause the dissociation of dinitrogen

tetroxide into some ionic species. From the data presented in Table

12, it can be seen that the freezing point depression is far less than

that which would be expected on the assumption that either of these

sulfides gives an addition compound with dinitrogen tetroxide in some

ionic form. The formation of a 1:1 ionic type compound-the usual










53

stoichiometry for addition compounds where the dinitrogen tetrrxide

is ionic-should lead to a freezing point depression of about 2.20,

at the concentration employed, for both of the sulfide-dinitrogen

tetroxide addition compounds. The degree of dissociation of an ionic

type compound into free sulfide and molecular dinitrogen tetroxide

should have no influence on the depression of the freezing point.

The removal of a molecule of dinitrogen tetroxide and molecule of

sulfide through the formation of an ionic type addition compound would

lead to no reduction in total number of species present since a cation

and an anion must be formed each time a molecule of dinitrogen tetroxide

dissociates. The formation of addition compounds containing molecular

dinitrogen tetroxide would, however, lead to a reduction in the total

number of species present. There could, of course, be some equilibrium

between a molecular type addition compound and an ionic type addition

compound. As given in Table 12, the freezing point depressions of

chloroform produced by the addition compounds of di-n-butyl sulfide

and di-isoamyl sulfide with dinitrogen tetroxide are 1.470 and 1.250,

respectively. These depressions are fairly small for the concentration

employed, and any such equilibrium could be expected to lie far to the

side of the molecular type addition compound.

In ummnary, three types of evidence indicate that ionic species

are absent, or at least unimportant, in the sulfide-dinitrogen tetroxide

addition compounds. These are as follows: (a) the instability of

the addition compounds under reduced pressure even at quite low










54

temperature with respect to dissociation into free acid and base;

(b) the relatively high solubility of the addition compounds in sol-

vents of low polarity; (c) the relatively small depression cf the freez-

ing point of chloroform caused by these addition compounds.

The possibility that nitrogen dioxide radicals may be involved

in the addition compounds is remote. Certainly the equilibrium be-

tween dinitrogen tetroxide and nitrogen dioxide radicals in chloroform

solutions at the temperatures at which the dielectric constant measure-

ments were made would be displaced far to the dinitrogen tetroxide

side. The dinitrogen tetrcxide-ohloroform solutions were absolutely

colorless before mixing them with the sulfide-chloroform solutions.

The phase diagram for the system chlorofora-diuitrogen tetroxide (32)

shows that no solid state compound exists between these substances,

and the mole number calculated from the cryoscopic data is consistent

with the dinitrogen tetroxide formulation. Studies of volume changes

occurring on mixing dinitrogen tetroxide and chloroform, at 00 and

below (33), show that the solutions are almost ideal. A very slight

positive deviation from ideality is noted, but even this deviation

decreases with decreasing temperature. It is recognized that the

absence of nitrogen dioxide radicals before mixing the dinitrogen

tetroxide-chleroform solutions and the sulfide-chloroform solutions

does not absolutely preclude their formation and subsequent reaction

after mixing the solutions. However, such a supposition lacks the

slightest support from any of the previously studied addition compounds










55

of dinitrogen tetroxide and Lewis bases. Accordingly, the existence

of nitrogen dioxide radicals in these addition compounds may be

considered to be highly improbable.

The conclusion most consistent with the facts is that the

sulfide-dinitrogen tetroxide addition compounds which were studied

contain molecular dinitrogen tetraxide. It is upon this basis that the

significance of the dielectric constant studies will be evaluated.


Dielectric Constant Studies. The capacitance, C, of a con-

denser is the ratio of the charge, Q, on one of its plates to the

difference in potential, V, between its plates.
Q
C --
V

The capacitance is a function of the physical dimensions of the

particular condenser which is used as well as the nature of the

dielectric, or insulation, between the condenser plates.5

The ratio of the capacitance of a condenser with some par-

ticular substance as the dielectric, CD, to the capacitance of a

condenser with no material dielectric, i.e., a vacuum between the

plates, CV, is the dielectric constant, E

C. D
CV


5Capacitance and, therefore, the dielectric constant are also
functions of pressure and temperature. However, since these inten-
sive variables are usually controlled, they do not represent additional
degrees of freedom in a given experiment.










56

In practice, dry air is usually used instead of a vacuum, since in

most work the difference in capacitance between dry air and a vacuum

is negligible. If the same condenser, under identical conditions, is

used to determine both CD and CV, the effects of the physical dimensions

of the condenser on these quantities will cancel when the ratio is

taken. It is thus unnecessary to know the condenser dimensions when

measurements are made with the same instrmen. The dielectric

constant is independent of the particular condenser used and is a

function only of the dielectric.6

The well-known Clausius-Mosotti equation relates the dielectric

constant to the total molar polarization, P, of the dielectric.


p E 1 M where, M is molecular weight
S+ 2 d d is density


This relation applies best to gases. When solutions are studied in

which one of the components is a non-polar substance, the assumption

is usually made that this relation still holds. If the mole fraction

of component 1 be denoted as N1 and the mole fraction of component 2

as N2, then the Clausius-Mosotti equation assumes the form:


p E 1 NjlM + N2M2 = N1iP + N2P2
S+2 d

If component 1 is taken to be the non-polar substance, then P1 is its

total molar polarization and is a constant throughout, and the quantity










57

N1Plvaries linearly with Nl. The quantity N2P2, and hence P2, is

then evaluated by difference. The changes of P2 with N2 are used to

analyze the association process which occurs in such solutions (34).

There are several reasons why the chloroform solutions of the

sulfide-dinitrogen tetroxide system which were studied are not amenable

to a treatment such as that just described. Chloroform is itself a

somewhat polar substance. Yet, it was necessary to find a solvent

which does not form a compound with dinitrogen tetroxide or with the

sulfides, and at the same time, the solvent had to have a low enough

freezing point to be a liquid at the low temperatures required to

prevent oxidation-reduction. A consideration of these two factors

strongly indicated use of chloroform as the solvent.

Even if a suitable non-polar solvent could have been found,

an investigation over a large concentration range would have been

impossible using the experimental technique previously described.

Dinitrogen tetroxide is far too volatile to make even moderately con-

centrated solutions by the relatively simple direct weighing method

used in this work. Even 0.1 molar solutions of dinitrogen tetroxide

in chloroform (a very good solvent for dinitrogen tetroxide) are quite

difficult to handle at room temperature without significant losses

of dinitrogen tetroxide. To investigate a wide concentration range,

more elaborate equipment would have been necessary. Should such

equipment have been made, there would still have been an element of

uncertainty in the interpretation of the results since three components










58

would have been involved-the solvent, dinitrogen tetroxide, and the

sulfide. Since one of the purposes of this study was to try to deter-

mine the stoichiometry of the sulfide-dinitrogen tetroxide addition

compounds, the necessary information to reduce the three variables

to two variables-solvent and addition compound--would have been

lacking. Whether one would have been studying the association of the

sulfides with dinitrogen tetrcaide, or the association among the re-

sulting addition compounds themselves, would not have been clear.

Undoubtedly, both of these effects would have manifested themselves

in the dielectric constant measurements. The separation of these

effects would pose a formidable, if not impossible, theoretical problem.

The fact that chloroform is somewhat polar has an advantage,

however. Its polarity gives rise to a dielectric constant, at the

temperatures employed, high enough to mask completely the contribu-

tions of the dinitrogen tetroxide and the sulfides in the separate

chloroform solutions. It is felt that the increase in dielectric

constant above that of the separate solutions (essentially pure

chloroform) is therefore attributable almost completely to the resulting

addition compound. The maximum concentration used was 0.065 molar

for the separate solutions of the sulfides and of dinitrogen tetroxide.

The formation of an addition compound can only lead to a final con-

centration of the addition compound which is less than the original

concentration of the separate solutions. It is reasonable to conclude

that the concentrations of all the addition compounds studied were small











59

enough to preclude significant interaction among the addition compound

molecules themselves.

Some interaction must occur between chloroform and the

addition compounds. To deny such an interaction would be completely

unjustified. Yet, it seems altogether justifiable to assume that

such solvation of the addition compounds by the chloroform is of a

similar nature for all of the compounds since the studies involved

an essentially homologous series of sulfides reacting with dinitrogen

tetraxide. If we proceed upon such an assumption, then, even though

a quantitative argument is of doubtful value, qualitative and semi-

quantitative trends shown by the dielectric constants of the various

sulfide-dinitrogen tetroxide systems can be interpreted in terms of

trends to be found among the addition compounds alone.

At the relatively low frequency used for the dielectric con-

stant measurements, the total molar polarization of any species is

composed mainly of two factors. First, there is the contribution

from the presence of any permanent electric moment or permanent

dipole moment. Second, there is the contribution from transitory or

induced dipoles which arise from the imposed electric field, and which

also may possibly arise from an electric field created by the nearby

presence of another molecule possessing a permanent or an induced

dipole. All molecules exhibit this second type of polarization to

some degree. Only in those molecules where there exists a permanent

asymmetry of charge distribution is the first type of polarization,











60

that caused by a permanent moment, exhibited.7

The magnitude of the permanent polarization is dependent

upon the temperature. The higher the temperature the greater the

thermal agitations of the polar species. This thermal agitation pre-

vents an efficient alignment of the dipole in the imposed electric

field, thus lowering the measured polarization. Induced polarization

does not show this temperature dependence.

Induced polarization is caoposed primarily of electronic

asymmatry produced by the imposed electric field or by the presence

of a field established by a neighboring species. The atoms of a

molecule may also have their nuclei slightly displaced by an imposed

electric field and hence contribute to the induced polarization.

However, since electrons are relatively mobile compared to the nuclei

of atoms, by far the more important factor of induced polarization is

the electronic effect. It will be assumed that electronic polarization

is the only induced polarization effect that need be considered in

the discussion of the sulfide-dinitrogen tetroxide addition compounds.


7A definite time, the relaxation time, is required for per-
manent dipoles to revert to a random distribution after the removal
of the impressed field. If the frequency of the alternating field
is of the same order of magnitude as the relaxation time, the dipole
cannot re-orient itself, and only induced polarization is measured.
Since the relaxation time for a wide variety of polar molecules is
of the order of 10-11 seconds, this effect does net appear until the
frequency of the field approaches 1010 cycles/second and almost
certainly is not present when the frequency is less than 10o cycles/
second.













We may write:

P P + PE where, Pu is the permanent polarization
PE is the induced (electronic) polar-
isation

and, as before:

p 1 M
u +E 6 +2 d

Since the assumption of non-interaction between chloroform and the

addition compounds cannot be made, there is no way to obtain a simple

relation for Pu + PE which would apply to the addition compounds

alone. However, if the assumption, previously discussed, that trends

in the total polarization may be largely ascribed to changes in the

addition compounds alone is valid, then we may say:


(Pu + PE) addn. O ( 1)
comp. (E + 2)


In Table 13, are listed values (multiplied by 103 for convenience) of

the quantity, ( E- 1) for the maximum dielectric constant measured
(E + 2)
for the sulfide-dinitrogen tetroxide systems. Also listed are the

relative changes in this quantity (and hence in the quantity Pu + PE)

in moving from addition compound to addition compound in the essentially

homologous sulfide series.

Basically, three points must be considered in discussing

the sulfide-dinitrogen tetroxide addition compounds and their electri-

cal behavior. These points are the following: (a) the trends













TABLE

T30LL.. RIZL ATIONS)
TEERIZDLAj)'.;T^ -I


T I, -6
. AT -60


System [ ( 1) ]l3
System 2) x 103 (P + P ) x 103
+ T X + 2


Dimethyl sulfide-dinitrogen 676
tetroxide

Diethyl sulfide-dinitrogen 683 +7
tetroxide

Di-n-propyl sulfide- 693 +10
dinitrogen tetroxide

Di-n-butyl sulfide- 692 -1
dinitrogen tetroxide

Di-isoamyl sulfide- O0 -2
dinitrogen tetroxide


presented in Table 13; (b) the reasons why not all the sulfide-

dinitrogen tetroxide addition compounds studied show a significant

increase in dielectric constant, and hence in polarization, over and

above that of chloroform, and the reason why none of the three

analogous ether-dinitrogen tetroxide systems studied produces much

change from the dielectric constant of chloroform alone; (c) the

significance of the stoichiometries indicated by the maxima of

figures 7 through 11. These three points will be considered in

order, as listed. Electric moment data, relative to the future

discussion, for some ethers and sulfides are presented in Table l1










63

(35), (36), (37). Included in these data are permanent dipole

moments in Debye units for the ethers and sulfides, and the induced

electronic polarization in cubic centimeters for the sulfides.


TABLE 14

ELECTRIC MOMENT DATA FOR SOME SULFIDES AND ETHERS


Substance u (Debye units) PE (c.c.)


Hydrogen sulfide 1.10 -

Dimethyl sulfide 1.40 19.1

Diethyl sulfide 1.57 28.46

Di-n-propyl sulfide 1.55 37.6

Di-n-butyl sulfide 1.57 46.9

Water 1.87 -

Methyl ether 1.29-1.32

Ethyl ether 1.10-1.1 -

n-Propyl ether 1.16 -



It has been recognized for some time that the replacement of

a hydrogen atom by a methyl group in a molecule has two chief effects

on a functional group in the molecule (38). The permanent polarization

and the polarizability of the molecule in question are likely to be

affected. Table 14 shows that as methyl groups successively replace

hydrogen atoms in the sulfides, there is a sharp increase in the











61

permanent dipole moment until diethyl sulfide is reached, after which,

further substitution of methyl groups has no significant effect. The

usual explanation for this behavior is that the greater polarizability

of methyl groups over hydrogen atoms allows the sulfur atom to draw

electrons to itself more efficiently. This effect is one of a permanent

induction along the hydrocarbon chain, which results in a greater degree

of permanent polarization within the molecule. However, this effect

dies out as soon as there is more than one saturated carbon atom

between the sulfur atom and the additional methyl group. This pheno-

menon is referred to as the "insulation effect" of saturated carbon

atoms. This effect explains why the permanent dipele moment remains

constant when diethyl sulfide is reached. In addition to increasing

the permanent polarization of the molecule, the substitution of rethyl

groups for hydrogen atoms also causes the functional group to display

greater polarizability. When the sulfides act as Lewis bases, there

must be present, of course, some Lewis acid-in this case, dinitrogen

tetroxide. An increase in the permanent polarization of the sulfide

would increase its strength as a Lewis base toward dinitrogen tetroxide,

by making the electrons more available to the dinitrogen tetroxide.

However, an increase in the polarizability of the sulfide would also

increase its strength as a Lewis base by making it easier for the

dinitrogen tetroxide to attract to itself the unshared electrons on

the sulfur atom. This greater polarizability does not manifest itself

until the sulfur atom is under attack by the dinitrogen tetraxide.










65

Naturally, the polarization and polarizability effects which

were discussed in the preceding paragraph would operate whenever a

sulfide-dinitrogen tetroxide addition compound is formed, regardless

of whether one happened to be measuring the dielectric constant of the

compound or not. However, that the presence of a methyl group in

place of a hydrogen atom does lead to a greater polarizability is

reflected in the PE term. The imposed electric field distorts the

molecules still more as methyl groups are substituted for hydrogen

atoms. Table 14, indeed, shows that the PE term continues to increase

regularly as methyl groups are substituted in the molecules.

It is now possible to suggest an explanation for the trend

in Table 13. The in rease in polarization of the diethyl sulfide-

dinitrogen tetroxide addition compound as compared with the dimethyl

sulfide-dinitrogen tetroxide addition compound reflects the increased

permanent moment of diethyl sulfide over dimethyl sulfide. The greater

dipole moment of diethyl sulfide probably leads to a greater separation

of charge, or permanent dipole moment, in the diethyl sulfide-dinitrogen

tetroxide addition compound. Furthermore, the greater pelarizability

of diethyl sulfide may allow dinitrogen tetroxide to cause greater

distortion of the eslfur atom in diethyl sulfide than in dimethyl

sulfide. Such an increased distortion of the sulfur atom should also

help to increase the permanent dipole moment of the diethyl sulfide-

dinitrogen tetroxide addition compound.

The increased distortion of the sulfur atom by dinitrogen











66

tetroxide in the diethyl sulfide addition compound as compared with

the dimethyl sulfide addition compound may also lead to a greater

induced polarization by the imposed electric field. At first, it may

seem unreasonable to suggest that increased displacement of the electrons

on the sulfur atom may make it easier to displace electrons even more

by application of an external field. But it must be remembered that

this discussion does not involve molecule s of diethyl or dimethyl

sulfides alone, but rather these molecules as they exist in an addition

compound with dinitrogen tetroxide. Attention can no longer be centered

on the sulfur atoms alone. It is simply being suggested that when,

by substitution of a methyl group for a hydrogen atom, the sulfur atom

is more easily polarized by dinitrogen tetroxide, the electronic

distribution of the resulting compound may be more susceptible to

displacement by an external field. For example, the more completely

the nitrogen atoms in a molecule of dinitrogen tetroxide gain control

of electrons from the sulfur atoms, the more completely the oxygen

atoms gain control of the electrons constituting the bond between the

nitrogen and oxygen atoms. The creation of the additional formal

charges on the oxygen atoms could lead to greater induced polarization.

The relatively large increase in polarization, noted in Table

13, of the di-n-propyl sulfide-dinitrogen tetroxide addition compound

over the diethyl sulfide-dinitrogen tetroxide addition compound probably

is a result of increased polarizability of the sulfur atom. The

permanent dipole moment of di-n-propyl sulfide is about the same as











67

that of diethyl sulfide because of the insulation effect. The greater

polarizability of the sulfur atom in di-n-propyl sulfide would allow

greater distortion by dinitrogen tetroxide and hence a greater per-

manent dipole moment in the di-n-propyl sulfide addition compound

as compared with the diethyl sulfide addition compound. Also, a

greater distortion may produce a greater subsequent induced polariza-

tion, as previously suggested.

The two remaining addition compounds in Table 13 not only

show no further increases in total polarization but even exhibit

slight decreases from the di-n-propyl sulfide-dinitrogen tetroxide

addition compound. One reason for this observation may be a steric

effect coming into play as the hydrocarbon chain lengthens in the

successive sulfide molecules. The relatively large n-butyl and isoamyl

groups could serve to decrease the total polarization of the addition

compounds in which they are present by limiting the number of mole-

cules of dinitrogen tetroxide in the addition compounds or possibly

by assuming such positions as to cause a slight cancellation of perma-

nent or induced polarizations, or perhaps both, in their addition

compounds.

It has now been suggested that three factors may cause the

trend to be found in Table 13. First, an increase in the permanent

dipole moment of the sulfide molecule leads to a greater permanent

dipole moment, and hence to a greater total polarization in the re-

sulting addition compound. Second, the polarizability of the sulfide











68

molecule increases as methyl groups are substituted for hydrogen atoms.

This greater polarizability may help to increase the permanent polariza-

tion of the addition compound and it may also help to increase the

induced polarization of the addition compound. Third, steric effects

may become an important factor as the hydrocarbon chains in the sulfides

lengthen. The first factor probably helps to increase the total

polarization of the diethyl sulfide-dinitrogen tetroxide addition

compound over that of the dimethyl sulfide-dinitrogen tetraxide

addition compound. This factor probably does not lead to further

increases in the total polarization of the sulfide-dinitrogen tetroxide

addition compounds involving sulfide homologs higher than diethyl

sulfide. The second factor probably contributes to an increase in

total polarization for each successive addition compound in the

series. The third factor probably becomes important in the di-n-butyl

sulfide-dinitrogen tetroxide addition compound. This factor would

oppose the second factor and tend to decrease the total polarization

of the addition compounds of higher sulfide homologs.

A few dielectric constant measurements at temperatures higher

than -600 (Tables 2 and 6) show a general decrease in polarization

with increasing temperature for the addition compounds. This fact

indicates the presence of a permanent dipole moment in these addition

compounds.

Bis-(chloromethyl) sulfide and dinitrogen tetroxide apparently

do not form an addition compound under conditions similar to those











69

employed with the other sulfides and dinitrogen tetroxide. The absence

of any color when the two are mixed and the lack of an increase in the

dielectric constant over that of chloroform alone suggest that no

compound is formed. Color is apparently a good indication of the

formation of an addition compound between an organic sulfide and

dinitrogen tetroxide. There is fairly good correlation between total

polarization and color. To some extent, the higher is the total

polarization of the addition compounds, the deeper red are their

colors. This effect is quite noticable among the addition compounds

where large changes in polarization occur. However, the colors of

both the di-n-butyl and the di-isoamyl sulfide-dinitrogen tetroxide

compounds are very deep red; in fact, they are a bit deeper red than

the di-n-propyl sulfide-dinitrogen tetroxide addition compound. The

differences in color, as well as the differences in polarization are,

however, fairly small for these three addition compounds. Shifts to

longer wave lengths in the colors of compounds are usually connected

with a general lowering of the energy of the system. The lack of any

color when an organic sulfide is mixed with dinitrogen tetroxide, at

low temperatures, can be ascribed to the lack of any lowering in

energy of the system, and thus to a lack of any strong interaction

between the molecules. The reason that bis-(chloromethyl) sulfide

does not form an addition compound with dinitrogen tetroxide, under

the same conditions as those for the other sulfide-dinitrogen tetroxide

systems, is probably because the rather electronegative chlorine atoms










70

decrease the electron density on the sulfur atom to such an extent that

electron donation by sulfur to dinitrogen tetroxide is not possible.

Reference to Table 14 shows that the ethers do not follow the

same trend as do the sulfides with respect to their permanent dipole

moments. The permanent dipole moments of the ethers do not increase

as methyl groups are substituted for hydrogen atoms; rather, just

the opposite effect is observed. Oxygen is not nearly as polarizable

an atom as sulfur. This fact plus the fact that the relatively small

size of the oxygen atom gives rise to a shielding or steric interference

by hydrocarbon chains (39) probably are primarily responsible for this

difference between the sulfides and the ethers. This reasoning also

explains why addition compounds between ethers and dinitrogen tetroxide

should show less polarization than the corresponding sulfide-dinitrogen

tetroxide addition compounds. The systems n-butyl ether-dinitrogen

tetroxide and l,4-dioxane-dinitrogen tetroxide in chloroform solutions

(Tables 9 and 11, respectively) show an almost negligible change in

dielectric constant from that of chloroform. The more basic tetra-

hydropyran shows a very slight increase in dielectric constant over

chloroform when mixed with dinitrogen tetroxide in the usual manner

(Table 10). These very slight changes in dielectric constant seem to

indicate that interaction is occurring, but that the total polarization

of the resulting compounds adds only slightly to the already moderately

high polarization of chloroform alone. If the relatively stable

cyclic structure of the l,4-dioxane-dinitrogen tetroxide addition










71

compound is retained in chloroform solutions, this structure could

perhaps lead to a partial cancellation of charge separation and help

to reduce the total polarization.

The data for the system l,1-dithiane-dinitrogen tetroxide

(Table 8) show a slight drift to higher dielectric constants as the

ratio of dinitrogen tetroxide to dithiane becomes very high. The

pale color which does appear, does so only after an induction period

following the mixing of the solutions. One possible explanation is

that when the stoichiometry is anywhere near equi-molar amounts of

dithiane and dinitrogen tetroxide, the structure of the addition com-

pound resembles that of the cyclic structure of the dioxane-dinitrogen

tetroxide addition compound. Calculations show that the dioxane

molecule in the "boat" form is sterically favorable for the formation

of a cyclic structure (2). In view of the much larger size of the

sulfur atom as compared with the oxygen atom, it is probable that an

analogous dithiane-dinitrogen tetroxide addition compound would not

be nearly as stable as the dioxane addition compound. Interference

between the sulfur atoms in the "boat" form of dithiane would be much

more severe than interference between oxygen atoms in the "boat" form

of dioxane. The "chair" configuration for dithiane is thermodynamically

favored, as would be expected (40), (41). It is likely that the con-

version from the "chair" to the "boat" configuration would require a

significantly higher activation energy in the case of dithiane than

for dioxane. The induction period before the appearance of a color










72

after mixing the dithiane and dinitrogen tetraxide solutions can be

explained as the time required for "chair" dithiane to convert to

"boat" dithiane and then collide with a dinitrogen tetroxide molecule

in precisely the right way to form the relatively unstable cyclic

structure. Increasing the ratio of dinitrogen tetroxide to dithiane

may lead to the interaction of more molecules of dinitrogen tetroxide

with the dithiane which has already formed the cyclic addition compound

with dinitrogen tetroxide. Since both ends of the same dithiane

molecule would be under attack by dinitrogen tetroxide molecules,

further steric hindrance would be likely. The net effect of the

unfavorable spatial arrangements would be less efficient electron

donation and acceptance and, consequently, a relatively low total

polarization.

Reference to the curves in figures 7 through 11 shows a change

in the position of the maximum of the dielectric constant curves for

the addition compounds as the sulfides are changed. Table 15 gives

the ratio of sulfide to dinitrogen tetraxide at the maximum dielectric

constant for these systems as read from the graphs.

The weakest base, dimethyl sulfide, forms a 1:1 addition com-

pound with dinitrogen tetroxide in chloroform solution. There is a

sharp change in the apparent stoichiometry for the diethyl sulfide-

dinitrogen tetroxide addition compound; the proportion of dinitrogen

tetroxide is much higher in the latter compound. After diethyl sulfide,

the remaining sulfide-dinitrogen tetroxide addition compounds show a




















TABLE 15

APPARENT STOICHIOIETRY OF THE SULFIDE DINITROGEN
TETROXIDE COLTOUNDS IN CHLOROFORM SOLUTION
FROM DIELECTRIC CONSTANT MEASUREMENTS


System Mole Ratio: R2S/N204 at Eax.



Dimethyl sulfide-dinitrogen 1:1
tetroxide

Diethyl sulfide-dinitrogen 1:2.5, or 2:5
tetroxide

Di-n-propyl sulfide- 1:2
dinitrogen tetroxide

Di-n-butyl sulfide- 1:1.5, or 2 3
dinitrogen tetroxide

Di-isoamyl sulfide-dinitrogen 1:1.5, or 2:3
tetroxide










7h

gradual reduction in the proportion of dinitrogen tetroxide. These

apparent empirical formulas for the addition compounds apply to the

compounds dissolved in chloroform. From the experimental data obtained

in this work, it is impossible to assess accurately the effect of the

solvent upon the apparent empirical formulas. Furthermore, epirical

formulas for the solid addition compounds could not be obtained.

Therefore, the discussion of the significance of these results in

solution cannot be assumed to apply necessarily to the solid-state

addition compounds.

The 1:1 stoichiometry observed for the dimethyl sulfide-

dinitrogen tetroxide compound is not at all surprising. The large

size of sulfur may sterically prohibit electron donation by two sulfide

molecules to a single dinitrogen tetroxide molecule even from opposite

ends of the dinitrogen tetroxide molecule. The fairly strong basicity

of the sulfide may allow partial donation of electrons to both nitrogen

atoms in dinitrogen tetroxide from the same sulfur atom. Some of the

more basic monofunctional ethers form 1:1 addition compounds with

dinitrogen tetroxide, as well as the N20OL2B type of compound.

The change to the relatively high ratio of dinitrogen tetroxide

to sulfide in the diethyl sulfide addition compound is probably a

reflection of the large degree of polarization of diethyl sulfide as

compared with dimethyl sulfide. Since electrons are more readily

available to dinitrogen tetroxide from diethyl sulfide, than from

dimethyl sulfide, a more favorable electronic distribution may occur











75
when more than one molecule of dinitrogen tetroxide takes part in the

electron sharing process. The large sulfur atom is probably not

sterically hindered to a great extent by the ethyl groups.

Di-n-propyl sulfide is more basic than diethyl sulfide, but

the propyl groups may exert enough steric hindrance to begin to limit

the number of dinitrogen tetroxide molecules which can efficiently

group themselves around the sulfur atom. As previously suggested,

the steric factor may become important with di-n-butyl sulfide and di-

isoamyl sulfide. This factor could explain the further decrease of

moles of dinitrogen tetroxide per mole of sulfide for these addition

compounds. As has already been pointed out, electronic effects tend

to lead to increased polarization of the addition compounds as the

hydrocarbon chain of the sulfide lengthens. However, steric hindrance

also increases as the hydrocarbon chain lengthens and may tend to

decrease the total polarization. Apparently the most favorable balance

between these opposing factors, as far as total polarization is concerned,

is found in the di-n-propyl sulfide-dinitrogen tetroxide addition com-

pound, as exemplified by the magnitude of the Emax. values. Per-

manent polarization and polarizability effects are high in this addition

compound and steric effects, though beginning to appear, do not seriously

interfere. As a result, the di-n-propyl sulfide-dinitrogen tet'oxide

addition compound shows the largest total polarization.

The R2S:N204 mole ratio of 1:2.5 for the diethyl sulfide-
dinitrogen tetroxide addition compound can, of course, be written











76

2:5, suggesting that perhaps more than one sulfide molecule is to be

found in a molecule of the addition compound. This argument is based

upon the assumption that only one complex is formed in the system and

that there is no complication, as was mentioned on page 15 of this

dissertation, arising from the presence of more than one equilibrium

in the system. These same possibilities also apply to the di-n-propyl

sulfide and di-isoamyl sulfide addition compounds, which also show

fractional mole ratios. The experimental technique employed may simply

be too insensitive to detect the true mole ratios. Even if this should

be the case, it is felt that the general discussion which has been

presented would be applicable.

Finally, we should consider the shape of the curves in

figures 7 through 11. There is a sharpening of the maximum as we pass

successively from the dimethyl sulfide-dinitrogen tetroxide system to

the di-isoasyl sulfide-dinitrogen tetroxide system. The simplest

explanation for this behavior is analogous to that employed to explain

variation of sharpness of maxima in temperature-concentration phase

diagrams viz., that "flatness" indicates dissociation of the compound

into its component parts. The sharper the maximum, the less is the

dissociation. In order to test this idea, a calculation, based on

cryoscopic measurements, of the degree of dissociation, of the two

addition compounds showing the same stoichiometry at the maximum in

their dielectric constant curves was made (Table 12). Di-n-butyl











77

sulfide and di-isoamyl sulfide show the same atoichiometry with dinitro-

gen tetroxide (Table 15). However, the di-n-butyl sulfide-dinitrogen

tetroxide system, according to the calculation, shows a higher

degree of dissociation than the di-isoamyl sulfida-dinitrogen tetroxide

system. Likewise, the dielectric constant curve for the di-n-butyl sulfide-

dinitrogen tetroxide system (Fig. 10) is not quite as sharp at its

maximum as is the curve for the di-isoamyl sulfide-dinitrogen tetroxide

system (Fig. 11). Though this one comparison does not prove this

reasoning conclusively, it at least presents evidence from a different

experimental source which is consistent with the interpretation which

has been suggested for the shapes of the dielectric constant curves.

If total polarization is assumed to parallel thermodynamic

stability, we are unable to explain why the di-n-butyl sulfide and

di-isoamyl sulfide addition compounds should apparently show less

dissociation according to the criterion of the shapes of the curves

while, at the same time, the di-n-propyl sulfide addition compound

should show the highest total polarization of the compounds studied.

The answer may simply be that although large changes in total polariza-

tion give an indication of relative stabilities, total polarization

may, nevertheless, not be a strict index of the thermodynamic stability

of the addition compounds. It has been pointed out that steric factors

may be responsible for decreasing slightly the total polarization of

the higher sulfide homolog addition compounds from the total polariza-

tion of the di-n-propyl sulfide addition compound. But this small











78
decrease in polarization does not necessarily reflect any decrease

in thermodynamic stability. The generally deeper red colors of the

addition compounds and the generally sharper maxima of their dielectric

constant curves as one proceeds up the homologous series of sulfides

actually indicates that thermodynamic stability increases throughout.


Oxidation of Dithiane with Dinitrogen Tetraxide. The only

puzzling aspect of the series of reactions associated with the oxidation

of l,h-dithiane by dinitrogen tetroxide is the formation of 1,4-

dithiane monosulfone as a sublimation product of the l,4-dithiane

o(-disulfoxide-dinitrogen tetroxide addition compound. The oxidation

of ditlhane by dinitrogen tetroxide to give mostly dithiane c<-disulf-

axide plus a little dithiane 3-disulfaxide was to be expected by

analogy with the oxidation of the aliphatic sulfides. The formation

of some addition compound between dinitrogen tetroxide and the disulf-

oxides was also to be expected by analogy with the aliphatic sulfoxides.

The reversibility of the reaction of dithiane o(-disalfoxide with

dinitrogen tetroxide proves that there is no rearrangement within the

molecules when the reaction is carried out at room temperature or

below. Strong heating does lead to rearrangement, however, and the

following mechanism for the formabion of dithiane monosulfone is offered

in an attempt to explain this fact.





















I


N204 + +


-.0
:0: :0:


H2 CH2C

4N

0 0


**


I/\
00


III


N20 +











80
Step I is the formation of some addition compound between dithiane

o -disulfoxide and dinitrogen tetroxide. The formation of such an

addition compound would give rise to a formal charge distribution as

indicated. A nitrogen to sulfur linkage, rather than a nitrogen to

oxygen linkage, is indicated for the addition compound since neither

the alkyl sulfon e nor dithiane disulfone form addition compounds

with dinitrogen tetroxide. Dithiane o(-disulfoxide is known to have

the "chair" configuration as pictured (42). The sulfoxide oxygen

atoms are approximately 3.5R from the other sulfur atom to which they

are not bonded. This distance is somewhat over twice the normal sulfur-

oxygen bond distance, but it is close enough for van der Waals forces

to operate. The presence of the dinitrogen tetroxide in the addition

compound could further reduce this distance, as indicated. The high

formal charge on the sulfur atom which is donating electrons to the

nitrogen would offer the possibility of the electronic rearrangement

at high temperatures as pictured in Step II. If such a rearrangement

occurred, the lorer oxygen atom would become positive and would migrate

toward the pair of electrons on the sulfur atom to which it was not

originally bonded. The final products are given by Step III.

Of course, the second oxygen atom which is added to one of the

sulfur atoms to give the sulfone may come from the dinitrogen

tetroxide molecule, but if so, the abstraction of oxygen from the other

sulfur atom remains to be explained. The suggested mechanism accounts

for all the observed facts.










81

Oxidation of Trithiane with Dinitrogen Tetroxide. Dinitrogen

tetroxide does not oxidize trithiane smoothly, as it does dithiane.

Apparently ring cleavage occurs with trithiane. Other Lewis acids

are known to cause ring cleavage with trithiane. Aluminum chloride

in benzene (3) and chlorine water (W4) both lead to the production

of free sulfur, among other things, when reacted with trithiane.

The amorphous nature of the residue from the reaction of

dinitrogen tetroxide with trithiane and its low solubility in a variety

of solvents suggest the formation of polymeric substances. Polymeric

ethylene sulfides are known (45), and it is not unlikely that products

of a similar nature are formed in this reaction.

















-'v "


At temperatures near -600, aliphatic and alicyclic sulfides

react with dinitrogen tetroxide to form Lewis acid-base type addition

compounds. Previous work had shown that at hi her temperatures,

oxidation-reduction occurs, I 1 2 to te rfo tion of t' err -

ing sulfoxides for the aliphatic sulfides. iTe T erset T-ork S sh

that a similar oxidation-reduction occurs "ith 1,hL-dlit i b t that

ri cleavage occurs tith trithiane to produce 'ce sui volatile

sulfur co..tr. substances, nd -A eric materials.

Evidence has been .:;',-s to s ow taa- the aciphiaic

sulfide-dirnitr) :l: 1 tetroxide addition >.. ncds contain nolecular

dinitro en tetroxide. In this respect, they resemble the ether-

dini',ro a1 tetroaide addition '.- .'.Uds. eac s o e diClctric

constants .' these s' 1 -d i 'r- .. troc:dde addition ._ and

also of sone of the ether-dini' o) .. ttroAd: sat oth in cihloro-

form soltions, indicate tr.t the s," a ad1'ition t'i "s

,are ch m 'o n 1 ois e.; adition corn ouads.

.i= fact cran be attrib ted to th olc ro ; t- s t .s

c i:.. ih Ithe lr. tr . i. .. ty te saulur

atoa thn ; f the ato oth of these a--ts can lead to a

, : : total polarization the .l-i.n--dinitro I tetroxide addition

82











83

compounds than of the ether-dinitrogen tetroxide addition compounds.

The relative total polarizations of the sulfide-dinitrogen

tetraxide addition compounds in chloroform solutions are found to

increase, at first, as methyl groups are substituted for hydrogen atoms

in the hydrocarbon chains of the sulfide molecules. A maximum in total

polarization is reached iaith the addition compound containing di-n-

propyl sulfide. Further substitution of iethyl groups in the sulfids

molecules gives addition compounds with dinitrogen tetroxide which

show slight decreases in total polarization from the di-n-propyl

sulfide-dinitrogen tetroxide addition compound. Three factors are

suggested as the cause of this trend. These factors are: (a) the

increase in the permanent dipole moment of the sulfides, as methyl

groups are substituted for hydrogen atoms until diethyl sulfide is

reached, leads to greater Lewis base strength in the sulfidos and,

consequently, to a greater permanent dipole moment in the resulting

addition compound; (h) the increase in the polarizability of the sul-

fides, as methyl groups are substituted for hydrogen atcas, can lead to

a greater permanent dipole moment and a greater induced moment in the

resulting addition compound; (c) the greater possibility for steric

hindrance from the hydrocarbon chains of the sulfides, as methyl groups

are substituted for hydrogen atoms, may lead to a reduction in the

permanent or induced moments, or perhaps both, in the resulting addition

compound.
Increases in thermodynamic stability of the sulfide-dinitrogen
tetroxide addition compounds apparently accompany large increases in











84

the total polarization of the compounds. Small changes in total

polarization of these addition compounds are, however, not necessarily

connected with their stability. There are indications that the

stability of the addition compounds increases continuously as higher

homologs of the sulfides are used, up through di-isoanyl sulfide.

The dielectric constant data were treated so that an analysis

using Job's method of continuous variations is possible. In chloroform

solutions, the addition compound between dimethyl sulfide and dinitrogen

tetroxide shows a 1:1 stoichiometry. The diethyl sulfide addition

compound shows a much higher ratio of dinitrogen tetroxide than the

dimethyl sulfide addition compound. A ratio of 1:2.5 (or 2:5) for

diethyl sulfide to dinitrogen tetroxide is found for this addition

compound. The ratio is 1:2 for di-n-propyl sulfide to dinitrogen

tetroxide, and 1l1.5 (or 2:3) for both di-n-butyl sulfide and di-

isoamyl sulfide to dinitrogen tetroxide. The large increase in the

proportion of dinitrogen tetrcxide to sulfide for the addition com-

pound involving diethyl sulfide as compared with the addition compound

involving dimethyl sulfide is interpreted as a reflection of the

increase in basicity of diethyl sulfide as compared with dimethyl

sulfide. The gradual decrease in the proportion of dinitrogen tetroxide

to sulfide in the remaining addition compounds is interpreted as

reflecting an increase in steric hindrance as the hydrocarbon chain

of the sulfide lengthens.

The lack of formation of a stable addition compound in











85
chloroform solutions of l,4-dithiane and dinitrogen tetroxide is

attributed to unfavorable steric effects. The possibility of partial

cancellation of separation of charges, and consequent decrease in

polarization, due to the formation of a cyclic structure, is also

considered. The lack of formation of an addition compound in chloroform

solutions of bis-(chloromethyl) sulfide and dinitrogen tetroxide is

attributed to a decrease in basicity of the sulfide resulting from the

presence of the relatively electronegative chlorine atoms.

Dinitrogen tetroxide and l,h-dithiane o(-disulfoxide form a

solid, white addition compound, which is stable at room temperature.

Consistent mole ratios of the disulfoxide to dinitrogen tetroxide

in this addition compound were not obtained. However, the ratio of

disulfoxide molecules to dinitrogen tetroxide is fairly high in the

compound. Sublimation of this addition compound at temperatures above

1500 leads to the formation of dithiane monosulfone. A mechanism is

suggested for this rather unexpected reaction.


































APPENDIXES













APPENDIX I

JOB'S METHOD OF CONTINUOUS VARIATIONS

Assume the following equilibrium:

A + nB ABn

Suppose that solutions of A and B are prepared, both with a concen-

tration of M moles per liter, and that they are mixed in varying

proportions while always keeping the total volume, V, fixed. Assuming

volumes are additive, this procedure will maintain a constant initial

total number of moles of A and B.

For convenience, the following notation will be used for the

system at equilibrium:

(A] CI

CBB] C2

[ABJ C3

The following relations hold at equilibrium:

(1) 1 M( x) C3 where, x = volume of solution B taken


(2) C2 - nC3

) K 3 assuming that the equilibrium constant may
eq CIC? be expressed in terms of concentrations.












If C3 is expressed as a function of x, by the measurement of a suitable
physical property as x is varied, the necessary condition for a.

maximum or a minimum in the function is:

(4) C3' 0 where, 0C is the first derivative of C3 with
respect to x.
From (3):

(3') C3 -KeqCC2n
Differentiation of (1), (2), and (3') with respect to x gives:

(1') Ci. -C 3

(2') C 2 "- M nC '


(3") C3' Keq(nC1C2n-C2'1 + C01C2n)

Applying (Q), (1'), (2'), and (3"1) become:
(1'') 01' = -
V
(2"') 02' M .

(3'") nCiC2' + Cl'C2 = 0
Substituting (1"') and 2 1) into (3 '):

(5) nC--L C = 0

Substituting (1) and (2) into (5):

(6) n(V x) x = 0
Solving (6) for n:

x
n V -x










89

This result means that the determination of the volume ratio (and

hence the mole ratio) of the components A and B which makes any

relation of C3 as a function of x a maximum or a minimum affords a

calculation of n.













APPENDIX II

CONSTANCY OF THE STPAmAJD DINITROGEN
TETR3XIDE-IN-CHLOROFORM SOLUTIONS

In order to determine the effect of loss of dinitrogen

tetroxide, through evaporation, on the concentration of the standard

solutions, some quantitative determinations were made on these solu-

tions after exposure to the air. Use was made of the disproportiona-

tion reaction which dinitrogen tetroxide undergoes in the presence

of the hydroxide ion.

N204 + 20H- NO2" + NO" + H20

Keq = 8 x 1028 at 27 (46)

Standard solutions of dinitrogen tetroxide of about 0.060

molar in chloroform were prepared. The solutions were exposed to the

air for several minutes and then five milliliter aliquots withdrawn

and titrated with standard sodium hydroxide solution. The titration

was followed with a Beckmann, Model G pH Meter.

The results showed that maximum losses were such as to displace

the actual volume ratios of the dielectric constant curves about 1.2

milliliters toward a higher proportion of the various sulfides. A

shift in volume ratio of 1.2 milliliters would not greatly affect the

mole ratio of sulfide to dinitrogen tetroxide at the maxima of the

dielectric constant curves. The 1:1.5 ratio for di-n-butyl sulfide

and di-isoayl sulfide to dinitrogen tetroxide would become approxi-










91

lately 1:1.h. However, it is felt that this error represents an

upper limit and does not reflect the actual losses encountered since

great care was taken to see that the solutions were not exposed to

the air any longer than was absolutely necessary.










92

APPENDIX III

ATTAINMENT OF TEMPERATURE EQUILIBRIUM
BY SOLUTIONS IN THE DIELECTRIC
COiSTAIIT MEASURING CELL

All physical constants are expressed in English units since

a function which was determined graphically was expressed in these

units (h7).

The following assumptions were made:

1. The solutions are dilute enough to be treated
as pure chloroform.

2. The conductivity of the thin glass measuring
cell may be neglected.

3. Convection may be neglected.

4. The original temperature of the solution
(just after mixing the pre-cooled separate
dinitrogen tetroxide and sulfide solutions)
is -31oF.

5. Shaking the measuring cell containing the
solution results in the solution assuming
the average temperature between the tempera-
ture of the solution at its surface and the
temperature at its center.

6. The effect of the nickel condenser plates
may be neglected.

The solution was pre-cooled for three minutes at -103oF, and

then given twenty minutes at -76F before taking the capacitance

measurement.

The following symbols are used:

4c temperature of solution at the center of the
measuring cell.










93
4s = temperature of the solution at its surface.

go = original uniform temperature of the solution.

m = mean temperature of the solution.
k mean therman conductivity of chloroform =
O.Oh8Btu/hr ft OF/ft

Cp = mean heat capacity of chloroform = 0.4lBtu/lb

P mean density of chloroform a 891b/ft
d = diameter of measuring cell = O.lO4ft
= k 0.048 = 0.00135
C p 89 x 0.l4
9 C' t3 d 2 a function of 0+
(, t, d) a function of determined graphically.
The following relation holds for this situation:

Il = e ( "o)f( (, t, d2)
Pre-cooling period:
&s -1030F

& = -310p

t 3 1hr
-0- =]-

it o 0.00135 0.0063
d2 20 x 0.0108&
f(o(, t, d2) 0.99

c = -103 (-103 + 31)(0.99)
9 = -320F
C
S0 + a -32 103 -67F
Im 2 2












Twenty-minute period

S* -760F

-o -670F

20 1
60 I-Srhr

o< t 0.00135 0.
=2 3 x 0.01o08 = 0.O16

f(c<, t, d2) 0.45

% -76 (-76 + 67)(0.5)
4c -720F


= -76 72 -7OF
Im 2

4 z -590C
This calculation predicts that the temperature reached by the solution

in the measuring cell is within one degree of the reported temperature

(-60). Assumptions 4 and 5 are very conservative and assumption 6

is reasonable since the heat capacity of a metal is relatively low.

Assumption 1 is undoubtedly quite justified and assumptions 2 and 3

probably very nearly off-set one another. It is felt that on the

basis of this calculation and from a few direct measurement, no

doubt can exist that thermal equilibrium was attained.




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