A study of the obsorption chararacteristics of the carbon-carbon double bond in the infrared

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Title:
A study of the obsorption chararacteristics of the carbon-carbon double bond in the infrared
Uncontrolled:
Absorption charactersics of the carbon-carbon double bond in the infrared
Physical Description:
vi, 81 leaves. : ill. ; 28 cm.
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English
Creator:
Pijanowski, Leon Stanley, 1931-
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Subjects / Keywords:
Absorption spectra   ( lcsh )
Infrared spectra   ( lcsh )
Molecular spectra   ( lcsh )
Infrared radiation   ( lcsh )
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bibliography   ( marcgt )
theses   ( marcgt )
non-fiction   ( marcgt )

Notes

Thesis:
Thesis--University of Florida.
Bibliography:
Bibliography: leaves 76-80.
Statement of Responsibility:
by Leon Stanley Pijanowski, Jr.
General Note:
Manuscript copy.
General Note:
Vita.

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University of Florida
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All applicable rights reserved by the source institution and holding location.
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aleph - 000545996
notis - ACW9954
oclc - 13161015
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Full Text











A STUDY OF THE ABSORPTION

CHARACTERISTICS OF THE CARBON -

CARBON DOUBLE BOND IN THE INFRARED











LEON S. PIJANOWSKI, JR.










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
April, 1963















ACKNOWLEDGEMENT


The author wishes to express sincere thanks to his

research director, Dr. Armin H. Gropp, for his advice and

encouragement in this research. He is also indebted to the

other members of his committee.

The helpful suggestions of some of his colleagues

were most appreciated.

The compounds contributed by Peninsular ChemResearch,

Dr. John Savory, Dr. George Butler, Dr. Paul Tarrant and their

graduate students were invaluable.

The author also wishes to acknowledge the financial

assistance of the General Motors Corporation which contributed

significantly in making this research possible.
















TABLE OF CONTENTS


Page

ACKNOWLEDGEMENTS . . ... ... ii

LIST OF TABLES . . ... ... iv

LIST OF FIGURES . . ... ... vi

Chapter

I INTRODUCTION . .. 1

II APPARATUS AND EXPERIMENTAL TECHNIQUE .... 18

Apparatus . ... 18
Techniques . ... 21
Origin and Purification of Compounds 26

III DISCUSSION OF RESULTS. . 27

IV SUMMARY . .... 74

BIBLIOGRAPHY . . ... ..... 76

BIOGRAPHICAL NOTE . .... 81















LIST OF TABLES


Table Page

1. C=C Stretching Bands of Terminal Olefins of the
Type CH2=CHR . .... .30

2. C=C Stretching Bands of Terminal Olefins of the
Type CH2=C(CH3)R . .... .33

3. Influence of Increase in Symmetry Upon C=C
Stretching Bands . .... .37

4. Effect of Substitution and Chain Length on C=C
Stretching Bands . .... .39

5. Effect of Fluorine Substitution in Small Molecules
on C=C Stretching Bands .... 41

6. C=C Stretching Bands of Substituted Ethylenes 43

7. Effect of Substitution at the a Carbon Atom on
the C=C Stretching Bands of Propylenes .. 45

8. C=C Stretching Bands of Substituted Perfluoro
Ethylenes . .... 46

9. C=C Stretching Bands of Substituted Propylenes. 50

10. C=C Stretching Bands of Substituted 2-Methylpropenes 52

11. C=C Stretching Bands of Substituted Fluoropropenes 53

12. C=C Stretching Bands of Some Fluorine Unsaturated
Compounds. . . ... 56

13. C=C Stretching Bands of Some Cyclic Monoolefins 59

14. C=C Stretching Bands of Terminal Dienes .... 61

15. C=C Stretching Bands of Conjugated Olefins from
the Pure Compounds . .... 63

16. C=C Stretching Bands of Conjugated Olefins from
Carbon Tetrachloride Solutions ... 65









Table Page

17. C=C Stretching Bands of Some Olefinic Silanes 69

18. C=C Stretching Bands of Some Olefinic Tin and
Phosphorus Compounds . .... .72

19. C=C Stretching Bands of Some Oxazines from the
Pure Compounds ................. 73














LIST OF FIGURES


Figure Page

1. Comparison of Resolving Power of Calcium Fluoride
and Sodium Chloride Prisms Using CH2=CHF 19

2. Absorption of Carbon Tetrachloride Overtone 24

3. Comparison of the Spectra of CH2=CHC1 and CF2=CFCN
with the Spectra of the Carbon Tetrachloride
Solutions . ..... .. .28 *

4. Spectra of CH2=CH(CH2)3CH3 from the Pure Compound
and the Carbon Tetrachloride Solution 34

5. Spectra of CH2=C(CH3)(CH2)2CH3 from the Pure
Compound and the Carbon Tetrachloride Solution 35

6. Effect of Substitution at the a Carbon Atom with
Substitution of Varying Electronegativities
on the C=C Stretching Frequency. ... 48

7. Effect of Substitution at the p and at the 7
Carbon Atom with Substituents of Varying
Electronegativities on the C=C Stretching
Frequency . . ... 54

8. Spectra of CH2=CHCH=CHCH3 and CF2=CFCF=CFCF3
and the Spectra of the Carbon Tetrachloride
Solutions . . ... 67

9. Spectra of CH2=CHCH=CH(CH2)2CH3,
CH2=CHCH=CH(CH2)4CH3, and CH2=CHCH=CH(CH2)7CH3
from the Pure Compounds . .... .68















CHAPTER I

INTRODUCTION


Vibrational infrared spectra are related to the energy

of vibrations of the atoms relative to each other in the molecule.

Considering this fact, one would not predict on general grounds

of molecular dynamics that such things as characteristic group

frequencies should exist. However, as long ago as the 1880's

it was realized by Abney and Festing (1), that the presence in

a molecule of a certain collection of atoms, known as a functional

group, was accompanied by the presence of an absorption band at

a particular frequency in the infrared spectrum of the molecule.

In more recent years, beginning with the pioneer work of

Coblentz (2) in the infrared, and stimulated by the discovery of

the Raman effect in 1928, the concept of characteristic group

frequencies has become firmly established. Many investigators (3-7)

have centered their interests on attempts to associate absorption

bands at specific frequencies with the presence of certain

chemical groups in the molecule, one rather comprehensive treatment

being that of Bellamy (8). The concept of characteristic group

frequencies is a main reason for the present widespread use of

infrared spectroscopy.

The present study is concerned with the influence of

intramolecular factors on the absorption characteristics of the








carbon-carbon double bond (C=C) stretching vibration. The general

range of these stretching vibrations is from 2000 to 1400 cm.-.

Before discussing the factors influencing double bond

stretching frequencies and their intensities, it is desirable

first of all to state the conditions which must be satisfied for

group frequencies to exist and appear in the infrared. The

simplest set of conditions occurs when the group consists of

a pair of atoms AB, one of which, A, is bound chemically only

to B. Under such circumstances, the molecule containing AB

will have one mode of vibration in which A will vibrate along

the AB line and B will move very little--the so-called AB--stretching

vibration. Vibrations of the neighboring atoms in the molecule

will not affect this vibration very much. This stretching

vibration resembles the oscillation of two bodies connected by

a spring and the same mathematical treatment, namely Hooke's

law, is applicable to a first approximation. For stretching of

the bond A-B, the vibrational frequency v(cm.- ) is given by

equation [1]


1 f 1/2


where c is the velocity of light, f the force constant of the

bond, and 4 the reduced mass of the system, as defined by

equation [2]

mAmB [
mA + mB


where mA and mB are the individual masses of A and B.








In order for the A-B stretching mode to appear in the

infrared spectrum, that is, to be "infrared active" and result

in absorption of energy from incident radiation, it is essential

that there be a change in the dipole moment of the molecule

during the vibration. A more detailed account of infrared

theory may be found in Herzberg (9).

The concept of localized group frequencies is, of

course, generally recognized as an over-simplification. The

approximate vibrational frequency of a link AB is determined

primarily by the elasticity of the bond as measured by the

force constant, and by the masses A and B. In a complex

molecule this is modified by the interplay of certain intra-

molecular factors, i.e., atomic mass, mechanical coupling,

symmetry, bond angle strain, conjugation, electronegativity,

mesomerism, and dipolar field effects. With so many potential

variables it is at first difficult to see why characteristic

group frequencies should exist at all, but it should be remembered

that many of these factors can be minimized in favorable

circumstances. The basic frequency is therefore reasonably

constant and shows only minor differences under the influence of

the above mentioned intramolecular factors. These minor

differences, however, lead to the important distinctions in

frequency which are so valuable in correlation work. In the

discussion which follows the various intramolecular factors are

considered, particularly with regard to the C=C stretching

vibration, and it will be seen that present understanding of the

factors varies greatly.









There is a good deal of evidence that the frequencies of

multiple bonds are generally not sensitive to the mass effects

of the substituent, unless these happen to be hydrogen or

deuterium atoms. Substitution of deuterium for a hydrogen atom

in the ethylene molecule has been reported (10,11) to result in a

decrease of the C=C frequency from 1623 cm.-1 to 1605 cm.-.

Halford (12) has shown that the C=0 stretching frequencies are

insensitive to mass changes of the substituents for all masses

greater than 12, and similar treatments are available for the

C-=N (13), and C=C (14) vibrations.

The effects of vibrational coupling on group frequencies

have been very ably discussed in a recent paper by Lord and

Miller (14), and are also covered by Bellamy (8). Coupling

occurs when two groups vibrating with reasonably high and

nearly equal frequencies are situated near to each other,

provided that they have the same symmetry. This explains the

relative freedom of multiple bonds from these effects, as it

is unusual for more than one double bond to be associated with

the same carbon atom. When this does happen, as in allene or

carbon dioxide, the resulting interaction is extremely strong

and the asymmetric and symmetric stretching frequencies are

very widely separated.

The effect of symmetry on group frequency may sometimes

become quite complex, for if the effective symmetry of a

functional group changes, the change in the group is sometimes

so drastic that it may even be regarded as a new group, with

new characteristic frequencies. Therefore, only two effects of








symmetry are considered, that on the coupling of vibrations and

that on intensities.

There are four requirements for strong coupling of group

vibrations: close proximity of the vibrating atoms, strong

forces between the vibrating groups, approximate equality of

the group frequencies, and identical symmetry of the group

vibrations. Two group vibrations must have the same symmetry

in order for them to interact or couple. This is an important

restriction for vibrations of highly symmetrical molecules like

acetylene, benzene, carbon tetrachloride, etc. For molecules

with very low symmetry the requirement is easily satisfied,

and interactions are more generally permitted.

The effect of symmetry on the intensity of a group

frequency in infrared absorption is quite pronounced. The

absence of a group frequency from a spectrum is often taken to

mean the absence of the group from a molecule. It is well

known that a vibration which is symmetric with respect to a

molecular center is forbidden to appear in infrared absorption

as, for example, the C=C stretching frequency in ethylene. When

the symmetry center is removed, as in propylene, the vibration

becomes active.

Formally speaking, assymetrical substitution of

acetylene should always make the C=C vibration active. If

the two substituent groups have equal electrical and mass

effects on the two carbon atoms of the triple bond, however,

the symmetry of the group is not changed and the group vibration

is extremely weak or unobservable in the spectrum. Thus








n-propyl n-butyl acetylene (nona-4-yne) shows no triple-bond

frequency in the infrared spectrum (15).

A closely related situation exists when symmetry results

in drastically reduced intensity because of the nature of the

group vibration. It is well known that the C=C frequency in

cyclic monoolefins is often very weak or missing from the

infrared spectrum. The simplest example is cyclobutene. In

this molecule there is a plane of symmetry perpendicular to

the C=C bond axis. This plane prevents the development of a

dipole moment parallel to the bond line during the double-bond

vibration, despite the fact that the motion of the carbon

atoms is along this line. Therefore, any dipole-moment change

produced by the vibration must take place in other bonds and

is expected to be very small.

The angles formed when a carbon atom bonds to other

atoms are quite definite. These angles are, approximately,

tetrahedral for four-coordinated carbon, trigonal planar for

three-coordinated carbon and linear for two-coordinated carbon.

Molecules whose over all structure causes a departure from these

angles for one reason or another are said to be strained. Strain

has a definite effect on bond strength, and consequently

frequencies are altered by strain.

When the C=C is present in a ring, the bond angles may

be distorted considerably from the trigonal. If the interior

angles are decreased below 1200 because the ring is small, the

double-bond frequency drops. Cyclopropenes are the exception to

this rule. Closs and Closs (16), Breslow and Peterson (17), and








others (18,19) have reported the C=C stretching frequency of some

cyclopropenes in the range from 1865 to 1755 cm.- In cyclo-

butene, where the interior angles are presumably 950 or less, the

frequency is 1566 cm.-1 (14,20), in cyclopentene the value is

1612 cm.-1 (14,21,22), in cyclohexene, 1646 cm.-1 (14,21,22),

and in cycloheptene, 1650 cm.-1 (14). Cycloolefin rings with six

or more carbon atoms are non-planar and can adjust the C=C angles

to approximately 1200. As a result, the ring strain is not noticeable

and no evidence is provided by the spectra for the effect on the

double-bond frequency of an increase in the interior angle beyond

1200. It is of interest to note that the C-H stretching frequencies

associated with a strained C=C also vary regularly with the amount

of strain, though in the opposite direction. Since an atom such

as an olefinic carbon has only one s orbital and two p orbitals

available for hybridization, an increase in the s character of one

bond must be counterbalanced by an increase in the p character of

another. The above results imply an increase in the directional

component of the C-C bonds, so that the C-H bonds take on more s

character, become shorter and their frequencies rise.

Jones et al. (23), have made a comparative study of

steroids containing ethylenic linkages at different positions

and have shown that the frequency of the maximum in the region

of the C=C stretching vibration (1580-1680 cm.- ) is specific

for a given location of the bond in the steroid molecule.

Henbest et al. (22), made a spectroscopic examination of steroids

containing disubstituted cis-double bonds in the various positions

in the rings. In the simplest steroid cis-olefins the frequency








order reported was A2> A3 1 >A6 > A11 ranging from 1653 cm.-1

to 1620 cm.-. Henbest et al. (21), recorded the spectra of

groups of compounds containing cis-double bonds in different

environments and reported that cyclohexenes substituted in the

three position still had a C=C absorption at 1651 cm.-l, however,

the C=C of cyclohexenes substituted in the four position absorbed

over a range from 1649 to 1662 cm.-1. Jones and Herling (24)

have reviewed past work and reported that steroids have a

characteristic C=C absorption between 1672 to 1619 cm.-.

This paper included 53 references with specific references for

C=C stretching bands.

The effect of conjugation has been recognized for a

good many years (25-28). When the double bonds are conjugated,

the C=C stretching frequency drops by 20 to 40 cm.-, and a

similar decrease is observed for C=0 stretching frequencies.

The electrons in a double bond are known to be relatively

polarizable, i.e., mobile under external influences, and when

two double bonds are conjugated, the electrons of the double

bonds are presumed to move to some extent into the single bond

located between the double bonds. This charge migration

strengthens the single bond and weakens the double bonds, and

therefore the C=C or C=0 force constant decreases with the

consequent decrease in the group frequency.

Despite the multiple bond's usual freedom from mass and

mechanical coupling effects, the frequencies of multiple bonds

vary widely. These shifts have been reported as due to inductive

and mesomeric effects of the substituents (28). This is borne








out by the results of more recent investigations (14,29,30),

and by the many quantitative relationships which have been found

between group frequency shifts and other physical properties

which depend upon the same factors (29,31). In special cases,

field effects can also give rise to frequency shifts but these

are relatively small and will not be further considered.

Inductive effects can lead to either a rise or a fall

in the frequency of a multiple bond depending upon its original

polarity. In a non-polar compound such as butene-2, the charge

cloud of the double bond is initially central. Replacement of

a methyl group by chlorine displaces the cloud away from the

bond center leading to a more polar bond of lower frequency.

When mesomerism is absent, the frequency shifts arising from

induction will be a direct function of the electronegativities

of the substituents. Contributions from ionic forms are usually

too small to have any significant effect upon the frequencies

of multiple bonds.

Mesomeric effects arise only in unsaturated molecules

and are subject to the steric restriction that the groups

producing the effect must lie in the plane of the double bond.

It is known that in the substituted ethylenes CH2=CHC1 and

CH2=CFCl the mesomeric effects give rise to only about 4-5 per cent

double bond character (32) so that in vinyl and vinylidene halides

this frequency should be a direct function of the sum of the

electronegativities of the RIR2 substituents. That this is

realized in practice is shown by the linear relationship found

by plotting the electronegativities of the RlR2 groups against









the observed CH deformation frequencies (29). In an unsaturated

compound in which the substituents at the double bond lie in

the same plane, it is to be expected that any mass insensitive

vibrations involving the double bond will be subject to the

resultant of both inductive and mesomeric effects, and the

frequency shifts following changes in the substituents should

be a quantitative measure of the resultant effect.

Mesomerism of the group of R-C=0 to the polar structure
+ I -
R=C-0 occurs through the donation of an electron pair from R.

It will always increase the polarity of the multiple bond and

lower its frequency. In the case of a C=C link it follows that

both induction and mesomerism will lead to lower frequencies,

and this is supported by the fact that, in general, no C=C

frequencies are found at significantly higher values than that

of the purely covalent butene-2. The only exception to this

are fluorinated olefins which form a special group which is

discussed below. The direct connection between the frequency

changes of normal olefins and the polarity of the double bond

is well shown by the smooth relationship which connects the

frequency shifts with the enthalpies of hydrogenation (33).

Conjugation and mesomerism both involve some degree

of delocalization of the electrons over the atoms of the

resonating group, and are therefore very sensitive to the

planarity of the bonds concerned. Steric factors which decrease

or increase the coplanarity of the systems will, therefore,

lead to frequency shifts by alterations in the contributions

of resonance forms.








Bellamy (34) states that ionic forms such as F-[FC=CH2]+

will not be favored if alternative mesomeric structures as

Cl =CH-CH2- of lower potential energy are available. The ionic

forms are therefore most likely to arise in compounds with

fluorine substitution as this element alone combines a very high

inductive power with a very limited capacity for mesomerism

due to its high ionization potential. Contributions from the

form F-(FC-O)+ may, therefore, play some part in the very

high carbonyl frequency (35) of COF2 (1928 cm.-1), and it is

suggested by Bellamy (34) that similar effects are responsible

for the abnormal C=C frequencies of fluorinated olefins.

The behavior of olefinic bonds with multiple fluorine

substitution has long presented a major group anomaly. Vinylidene

fluoride (36) absorbs at 1728 cm.-1, and the frequency rises

steadily with further substitution to 1872 cm.-1 (as shown by

Raman spectra (37)) in perfluorethylene. Torkington and

Thompson (38) measured the infrared absorption of a number of

partially and fully fluorinated ethylenes and related compounds,

and correlated the band contours with the molecule structure and

attempted to assign the normal vibration frequencies. Many

other fluoroethylenes and related compounds have been studied

extensively and all of the fundamental vibrating frequencies of the

investigated samples have been assigned (39-49). Morino et al. (50),

using a normal coordinate treatment calculated the mean amplitudes

of the thermal vibrations in CF2=CF2 and CH2=CF2. Mann et al. (51),

performed the normal coordinate analysis of the fundamental

vibrations of 27 perhalogenated ethylenes which contained F, Cl,









or Br, and comparison with experimental results have been made

where possible and indicate good agreement.

In the fluoroethylenes, the C=C frequency rises

significantly above the value of 1675 cm.-l of the covalent

bond of butene-2, suggesting that some unique property of

fluorine is involved. Bellamy (34) suggests that ionic forms

such as -F[FC=CH2]+ might then make some larger contribution

than normal to the final structure of fluoroethylenes. It has

already been noted that the C=C frequencies of normal olefins

are directly related to the enthalpies of hydrogenation and the

frequencies fall as the reactivity rises (33). This situation

has been shown to reverse for fluorinated olefins and for

frequencies above 1675 cm.-1, the reactivity rises steadily

with the frequency (33). This is consistent with the idea of

ionic contributions which would lead to more reactive double

bonds. Bellamy (34) also states that it is not necessary to

postulate the existence of triple bonded structures to account

for the high C=C frequencies, as the orbital of the fluorinated

carbon atom which forms the C-C a bond in -F[FC=CH2]+ must have

a bigger proportion of s character than in the normal trigonal

state, and this will result in a shorter C-C distance and a

higher frequency. The F-C-F angle of CF2=CH2 closes down (52),

by as much as 100 to 1100; this would be expected if the carbon

orbital directed towards the CH2 carbon atom were taking on an

increased s character.

Edgell (53) recorded the Raman and infrared spectra of

C3F6 and assigned the fundamental vibration frequencies thereby








proving that C3F6 was hexafluoropropene and not a cyclic compound

as first was suspected. Brice et al. (54), have reported the C=C

stretching frequencies for a short perfluorobutene series. Some

cyclic perfluoroolefins have been investigated by Burdon and

Whiffen (55) and the C=C stretching frequencies reported for the

perfluorobutene, perfluoropentene, and perfluorohexene series

are 1799, 1754, and 1746 cm.-1, respectively. This is exactly

the inverse of the same cyclic hydrocarbon series and no

explanation was presented.

Haszeldine (56) has reported the C=C frequencies of a

series of partially and fully fluorinated olefins. The range

of frequencies for these series extend from 1613 to 1795 cm.-.

Haszeldine (57) in a later paper states that terminal

fluorinated olefins absorb at 1799 cm.-1 and that internal

fluorinated olefins have an absorption band at 1733 cm.-.

Simons (58) gives a brief review of fluorine containing olefins

and lists their C=C stretching frequency together with references

to the original articles.

Infrared absorption bands associated with the various types

of double bond found in hydrocarbons have been extensively studied,

so that recognition of the presence and type of unsaturation in

an unknown compound is usually possible with reasonable certainty.

Bellamy (8) gives the range of 1680-1620 cm.-l for non-conjugated

C=C stretching vibrations. Gullikson and Nielsen (59) recorded

the infrared spectra for gaseous samples of the vinyl halides and

assigned the fundamental frequencies. These values agreed quite

well with the earlier reported work of Thompson and Torkington (60).








Sheppard (27) and others (61,62) have studied some propene and

butene series and have assigned all the normal modes of vibration.

The infrared spectra of the vinyl compounds of mercury, cadmium,

zinc, tin and phosphorus have been investigated by Kaesz and

Stone (63), who report values for the C=C stretching frequency

from 1595 to 1565 cm.- with an accuracy of -5 cm. -

Sheppard (64), McMurry and Thornton (65), and Sheppard

and Simpson (66), presented three independent reviews which

have definitely narrowed the range of frequencies in which

different types of olefins absorb.

Sheppard (64) lists the following frequencies for the

olefin types: CH2=CHR, 1645 cm.-1; CH2=CRlR2, 1650 cm. -

RICH=CHR2(trans), 1675 cm.-1; RICH=CHR2(cis), 1660 cm.-1;

RICH=CR2R3, 1675 cm.-l. Sheppard also used line figures to

give approximate measures of absorption intensity.

McMurry and Thornton (65) in most cases give a narrow

range of frequencies for the olefin types: CH2=CHR, 1645-

1639 cm.-1; CH2=CRIR2; 1661-1639 cm.-l; R1CH=CHR2(trans),

1667 cm.-1; R1CH=CHR2(cis), 1661-1631 cm.-1; RICH-CR2R3

1692-1667 cm.-l. These coworkers also reported the lowest and

the highest absorptivity coefficient recorded for each type of

olefin.

Sheppard and Simpson (66) report an average value of

the C=C frequencies of the olefin types: CH2=CHRI, 1643 cm.-1.
-i -
CH2=CR1R2, 1653 cm.- ; RICH=CHR2(trans), 1673 cm.-l; RCH=CHR2(cis),

1657 cm.-l; R1CH=CR2R3, 1670 cm.-1. No intensity data are given

in this review. The values given in the three works have also

been reported independently by other investigators (67-69).








Rasmussen et al. (70), Theus et al. (71), and several

other researchers (72-75) working with cis-trans isomers of

compounds have confirmed the general rule that the trans

isomers have a stretching frequency that is 10 to 20 cm.-1

higher than the cis isomers.

The characteristic olefinic absorptions of a number of

polar allyl, vinyl, and isopropenyl compounds have been measured

in solution by Davison and Bates (76). New correlations were

established for the esters, ketones, and ethers. The correlations

for acrylates and methacrylates include absorptions associated

with the ester group. Conjugation explained some of the shifts

of the C=C stretching frequency and an additivity rule was

suggested and tested but the results were inconclusive.

Rasmussen et al. (77) reported that experimental data

indicated that at room temperature the trans form of 1,3-butadiene

predominates. Cis-butadiene is the lower energy form. The cis

form predominates at the temperature of a dry ice bath, while

at room temperature the trans form predominates. Rasmussen

and Brattain (78) recorded the spectra of 1,3-butadiene,

1,2-butadiene, isoprene, and cis and trans 1,3-pentadiene

vapor. They report absorption bands at 1605 and 1594 cm.-1

for 1,3-butadiene, isoprene has two bands at 1612 and 1603 cm.-,

and cis pentadiene showed two bands at 1656 and 1608 cm.-, and

finally trans pentadiene absorbed at 1661 and 1610 cm.-.

From the infrared spectra of various types of conjugated

ethylenic and acetylenic compounds, Allan, Meakins, and Whiting (79)

established correlations facilitating the recognition of these








systems. In many of the compounds investigated geometrical

isomerism was possible. Examination of both cis and trans

isomers led to useful spectral distinctions between them.

Blout et al. (80) determined the infrared spectra

of 26 compounds containing two or more conjugated double bonds

in the region of double bond vibrational absorption. Polyene

aldehydes and polyene azines show at least one strong absorption

maximum which shifts toward lower frequencies as the length of

the conjugated system is increased.

In infrared measurements of some of the compounds in

which isopropylidene-isopropenyl isomerism was possible, there

appeared to be an inverse relation between the C=C stretching

frequency of the isopropylidene groups (range 1656-1680 cm.-1)

and the corresponding out-of-plane hydrogen bending frequency

(range 812-858 cm.-l). Werner and Lark (81) collected data to

investigate this point and a statistical analysis was carried

out on values from 31 compounds having the group R1R2C=CR3H.

This has been extended to include a skeletal vibration frequency

(range 789-810 cm.-l) which appeared when the group in question

formed part of a cyclohexenyl ring.

This analysis revealed highly significant correlations

between the bands and yielded two sets of regression equations

of possible value in structural investigations.

In order to calculate the higher variation of the higher

normal frequencies in the chain of conjugated polyenic aldehydes,

Scrocco and Salvetti (82) introduced an interatomic potential

and used it to derive the corresponding secular equation. The








calculations showed that the highest frequency is basically due

to the valency oscillations of the C=0 group; the next highest

frequency is mainly determined by the oscillation of the C=C

group with highest binding energy, and so on. Agreement with

experimental results is satisfactory for the first two terms

of the series. The experimental data available at present are

not sufficient to draw definite conclusions concerning the other

terms.

Many other informative studies on the 2000 to 1400 cm.-1

region have been conducted. The above discussion was limited

to those works which were of interest in the present study.

For a more extensive bibliography on infrared studies a text

on that subject should be consulted. Bellamy (8) lists many

references at the end of each chapter in his text. Most of

the articles consulted in this study gave further references.

Although a great deal of work has been done on the

C=C stretching region of the infrared spectrum, it still holds

many unanswered questions. This present study was carried out

with the hope of elucidating some of these problems by illustrating

that C=C are not sensitive to mass effects above a mass of 12

and also to illustrate the relationship between the C=C stretching

frequency and the inductive effect of various substituents.














CHAPTER II

APPARATUS AND EXPERIMENTAL TECHNIQUE

Apparatus


A Perkin-Elmer Model 21 double-beam infrared recording

spectrophotometer was used in this research. This spectrophotometer

is normally equipped with a sodium chloride (NaCl) prism, but is

designed in such a way that the prism can' be changed. It was

decided to use the calcium fluoride (CaF2) prism, which has

better resolution than the NaCl prism in the range of this

investigation. Figure 1 illustrates the difference in the

resolving power of the NaCl and CaF2 prisms.

The range of the spectrophotometer with the CaF2 prism

is from 5000 cm.-I to 1050 cm.-1. This study, however, was

concerned only with the C=C stretching region which lies between

2000 and 1400 cm.-.

For a more detailed description of the spectrophotometer

and the ranges and resolving power of the various prisms, the

manuals prepared by the Perkin-Elmer Corporation should be

consulted.

Whenever the prism of the spectrophotometer is changed

several calibrations must be made. These are also described in

the manuals which are supplied with the prism and its interchange

unit.










Frequency in cm.-I


1500


1800


Sodium Chloride


Calcium Fluoride


Figure l.--Comparison of Resolving Power of Calcium Fluoride and
Sodium Chloride Prisms Using CH2=CHF.


1800


1630


1630


1500


_ 1








Because the research was concerned only with the range

of 2000 cm.-I to 1400 cm.-1 and to increase the accuracy of the

recorded frequencies, changes were made in the procedure given

in the manual for calibration of the frequency. The bands

usually used for calibrating the CaF2 prism are the 1340 cm.-1

atmospheric H20 band at low frequencies, and the 3335 cm.1

NH3 band or the 3741 cm.-1 atmospheric H20 band at high frequencies.

Instead of employing the recommended frequencies, the atmospheric

H20 bands at 1870, 1773, and 1637 cm.-l were used for calibration

and resulted in a frequency accuracy of -1 cm.-1 over the range

of frequencies utilized in the research.

A frequent check was made of the frequency using the

1870, 1773, and 1637 cm.-1 atmospheric H20 bands. Since

frequency remained constant, no adjustment was needed until

the prism was changed.

The procedure followed for the zero setting of the

spectrophotometer was that prescribed in the manuals prepared

by the Perkin-Elmer Corporation. Before each spectrum was

determined, the zero setting was checked and was adjusted

whenever necessary.

The spectrophotometer instruction manual recommended a

slit program dial reading of 987 which resulted in a slit width

of 91 microns at 2000 cm.-, and a slit width of 147 microns

at 1400 cm.-. In order to obtain maximum resolution of the

instrument, the slit program dial reading was decreased to

give narrower slit openings. A slit program dial reading of

950 was used, which gave a slit width of 50 microns at 2000 cm.-1









and a slit width of 84 microns at 1400 cm.- The narrower slit

widths employed resulted in a resolution of 3 cm.-1 over the

previously stated range of frequencies.

All spectra were determined with the gain set as

illustrated in the instruction manuals. The scanning time was

generally about 10 minutes per micron. When a major band

appeared, the speed was further reduced and the instrument

stopped at the peak of the band, and the frequency was then

recorded from the counter on the prism drive. A minimum of

three spectra of each compound was recorded to determine the

amount of absorption of each major band, and the reproducibility

of peak absorption was within the .5 per cent tolerance quoted

in the instruction manuals. The concentrations of the compounds

investigated were prepared to give an absorption between 50 per

cent and 80 per cent for the major bands. For some of the liquid

samples, as for some solutions, the available cell size prevented

such as absorption.



Techniques


Since the compounds under investigation were in the

gaseous, liquid, and solid states, a variety of techniques was

needed. The gaseous samples were run in a gas cell of 5 cm.

path length. The cell was first evacuated, the gaseous sample

was then allowed to fill the cell to the desired pressure, and

the pressure was measured with a manometer attached to the gas

cell filling apparatus. The pressure at which the samples were







run depended on that required to give the major bands an absorption

between 50 per cent and 80 per cent. The pressure varied among the

samples depending on the infrared activity of the compound being

studied. The extremes were 2 mm. Hg pressure for some unsaturated

fluorine compounds and 300 mm. Hg pressure for some unsaturated

hydrocarbons.

Carbon tetrachloride solutions of known concentration of

the compounds that are gases at room temperature were prepared.

The gaseous samples were condensed in a "Dry Ice" and acetone

bath and then quickly transferred, as liquids, by a length of

cooled small bore tubing to volumetric flasks containing carbon

tetrachloride. The volumetric flasks were weighed before and

after addition of the sample, and the difference equaled the

weight of sample put into solution. The volumetric flasks

were filled to their calibrated capacity after sufficient

time was allowed for the solution to come to room temperature,

since the condensed gases produced a cooling effect upon

addition to the carbon tetrachloride.

The prepared solutions were run in fixed cells of

various thickness to give the major band an absorption between

50 per cent to 80 per cent. The sizes of the fixed cells

utilized in the solution study were 0.048 mm., 0.099 mm.,

0.214 mm., 0.49 mm., and 0.93 mm. The thickness of all cells

used was accurately determined by the interference fringe

method of Smith and Miller (83).

Generally when compounds are run in solution, two cells

of approximately the same size are used. One contains the









solution and is placed in the sample beam while the other

contains only the solvent and is placed in the reference beam.

This allows the instrument to compensate for any band due to

the solvent. Carbon tetrachloride has an overtone absorption

band at approximately 1550 cm.-l, which becomes quite appreciable

when using cells of 0.1 mm. or greater thickness. Figure 2

shows the overtone absorption band produced in a 0.214 mm. cell,

and also illustrates effective compensation.

The spectra of most of the solutions were recorded

without any interference from the overtone absorption band of

the solvent. However, difficulty was experienced in determining

the amount of band absorption for a few solutions which required

the largest size cell, and where the sample absorbed at approx-

imately the same wavelength as the carbon tetrachloride overtone.

The problem encountered was due to partial compensation of the

sample peak by the carbon tetrachloride in the reference beam,

and prevented the determination of the amount of sample absorption

in this solvent.

A large number of the compounds investigated were liquid.

This included compounds with varying degrees of absorption, and

therefore various sample sizes were needed. The compounds with

high absorption such as the unsaturated fluorine samples, were

run in demountable cells. Since the absorption of the unsaturated

hydrocarbons was weaker than the fluorine compounds, fixed cells

were used. The cell size was determined by obtaining the desired

amount of absorption. Three different cell sizes were used to











Frequency in cm.


2000


1650


Curve A


Curve B


Figure 2.--Absorption of Carbon Tetrachloride Overtone Band in
0.214 mm. Cell.
Curve A: Compensated
Curve B: Uncompensated


1400








run the pure liquids. These were the 0.019 mm., 0.0246 mm.,

0.048 mm., and 0.214 mm. fixed cells.

The liquid samples were run in carbon tetrachloride

solutions. These solutions were treated in the same manner

as the solutions of the gaseous samples. However, due to the

weak absorption characteristics of some of the liquid samples,

the 3.0 mm. fixed cell, which is the largest cell available at

this laboratory, had to be used.

The solid compounds required more time for investigation

than either the liquids or gases. There are several methods for

obtaining the spectra of solids. A list of most of these methods

in given by Silas (84), and the technique manuals prepared by

the Perkin-Elmer Corporation. In this investigation only three

methods were used. The solids were run as mulls, potassium

bromide disks, and in solution. The mull method suspends a

finely ground sample in some mulling oil or grease. The

mulling oil used in this work was a mineral oil, generally

called Nujol.

Potassium bromide disks are prepared by mixing a

finely ground sample with some finely ground potassium bromide,

and the mixture placed in a special die where it is subjected

to high pressure under a vacuum. The product of this treatment

is a clear disk of potassium bromide with the sample imbedded

in it.

Carbon tetrachloride solutions of the solids were run

as described above. Two substituted ureas and two allyl ammonium








bromide salts were insoluble in carbon tetrachloride, and no

appropriate solvent could be found.



Origin and Purification of Compounds


All of the compounds used in this investigation were

obtained either from the laboratories of this University or

commercial companies.

Dr. John Savory and Dr. Paul Tarrant, and his group

of the Chemistry Department supplied most of the unsaturated

fluorine compounds. Dr. George Butler, and his group, of the

Chemistry Department furnished many of the unsaturated hydro-

carbons. Peninsular ChemResearch contributed the majority of

the samples which were not available from University laboratories.

Those compounds used in this study which were not obtained from

the above sources were purchased from commercial companies.

A few of the compounds had to be repurified. Distillation

at atmospheric pressure was used to purify the liquids.

A gas chromotograph, equipped with a column packed with

diamylphthalate on chromosorb,was used to remove impurities from

the gaseous samples.















CHAPTER III

DISCUSSION OF RESULTS


The spectra of all samples studied were obtained from

the pure compound and whenever possible from carbon tetrachloride

solutions. The compounds were recorded from the carbon tetrachloride

solutions to eliminate the rotational contours which appear in most

of the gaseous samples, and because spectra recorded from solutions

generally produce sharper peaks which facilitate accurate

determination of band position. A comparison of the difference in

spectra recorded from the pure gaseous sample and from the carbon

tetrachloride solutions, is illustrated in Figure 3.

The values of the.various frequencies for the pure

compounds and the carbon tetrachloride solutions are listed in

the tables in this chapter. The values in parenthesis indicate

peaks which appeared on the sides of the major band. The

following notations are used to indicate the relative band

intensities of the pure compounds: vs = very strong, s = strong,

m = medium, w = weak, and vw = very weak. Notations are not

used with the solution frequency values since the molar

absorptivities, calculated mainly from the carbon tetrachloride

solutions, are listed to the right.

The molar absorptivities were calculated from peak

heights through the use of the "Beer-Lambert Law" which was












Frequency in cm.-I


1710 1525 1870 1650 1905 1680
I I I I I I


Solution


Pure


CH2=CHC1


Solution


CF2=CFCN


Figure 3.--Comparison of the Spectra of CH =CHC1 and CF2=CFCN
with the Spectra of the Carbon Tetrachloride Solutions.


1725


Pure









assumed to hold true for the concentration of solutions used.

The values obtained were used as an aid in the qualitative

interpretation of the spectra.

The molar absorptivity (85), E, is defined as the

product of the absorptivity, a, and the molecular weight of the

substance, M.W.,


E = a(M.W.)


where the absorptivity, a, is equal to the absorbance, A, divided

by the product of the concentration of the substance (in g./l.) and

the sampel path length (in cm.),


A
a be


Molar absorptivity, E, will be listed in the tables in units

of M/l./cm.

The C=C stretching frequencies of the CH2=CHR type

olefins listed in Table 1 agree very well with values given

by Davison and Bates (76), and McMurray and Thornton (65), and

the average value of the solution frequencies omitting ethylene,

is 1643 -2 cm. The molar absorptivity values listed in the

table also fall within the range of values reported by the

above mentioned workers (65,76). The consistency of the C=C

vibrational frequency confirms what was predicted in Chapter I

and proved by this study that an increase of mass above 12 has

little effect on the C=C vibration.














w


4-\



0 '
- 4J \








oC






C)v











0











;-4


0
I l

















































0
o
o

0
O


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S Co CO) It r











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\'0 \0 \0 \0 %O
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v0
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Hl rH rH


II


0






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03


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0 *



CO CO CO CO CO 0 0
m 0 0 a 0 0 a
SC- 0 0 0 0 Z 0

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0 N C 4 Cl N c CN
Co C 4 a



C4 cq C14 CM C14 Cl Cl Cl C14 CM4


C4 CO lO
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in H C
^^ IT
\o0 0 \O
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cz E 65 E w
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CM 10 \0 10 I 110
\0 '0 \'0 0 '.0 '0
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E F E V u)
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~



































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0









0
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Table 2 lists the C=C stretching frequencies of the

CH2=C(CH3)R type olefins. The average value of the C=C solution

bands is 1651 1 cm.-l excluding CH2=C(CH3)H. The molar

absorptivity values and the average frequency value agree well

with the values listed by the aforementioned workers (65,76).

As in the previous series, the consistency of C=C frequency proves

the absence of any mass effect except for that in the first

compound.

The increase in frequency of the C=C absorption band

of the compounds listed in Table 2 is about 8 cm.-1 over those

compounds listed in Table 1. Since the electronegativity of a

CH3 group is a little less than that of the H atom, the increase

is not due to an electrical effect. A mass effect would lower

the C=C stretching frequency of CH2=C(CH3)R type olefins as

compared to CH2=CHR type olefins. The increase in frequency

is explained as a result of a loose type of coupling in which,

as the C=C vibrates the C-R bond has to bend a little in order

for the molecule, as a whole, to maintain its center of mass.

Since the CH3 group is heavier than the H atom, it is entirely

plausible that as the C=C stretches it will require more energy

to bend a C-CH3 bond than a C-H bond, thereby increasing the

frequency of vibration bf the C=C.

In almost all compounds listed in Table 2 as well as

some compounds in Table 1, a small side peak appears at the

consistent frequency of 1657 1 cm.-1. Figures 4 and 5 illustrate

the 1657 cm.-1 peak as it appears in the CH2=CHR and CH2=C(CH3)R
















S>u
c '0 CI) 110 o rH) )

0





o -i r-l r- O o l r O
L O L L) LO ) LV tn LO
0 \00 0 '0 '0 %0 '.0 \0
H H H H H H H -
: N r- \0 %0 '\0



O '-O
s0 '0 'o \0 '0 \0 \0











P LO O






0 0 H H H H H H H
c 'J


0\0
SH
E
0


'%0
z

LI) V) V) LI) LI) LI LI)












E -1 E M L M M M M L )
0 /3n m i i i S io
0 N 3 "> \0 \0 \0 '0 \0 \0 \0





O O N o
o N 04 BY 6 ) io ira



E-c (^




0 t
'>





e ~H





0 0



CV0 CI4 04 0 C C4 0

nC -) C I V O i)
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0-) CO CI O CV) CO CIO CV) CO CV





0 0' 0 0 0 0 0 0 0














Frequency in cm.-l


1700


1540


1900


S1700


1656-


1657-


Pure


Solution


Figure 4.-Spectra of CH2=CH(CH2)3CH3 from the Pure Compound and
the Carbon Tetrachloride Solution.


1900


II


1700


1540














Frequency in cm.


1700


1657-/


1 540A


. 1900


1700


1657


Pure


1 540
17VV n


Solution


Figure 5.--Spectra of CH2=C(CH3)(CH2)2CH3 from the Pure Compound
and the Carbon Tetrachloride Solution.


1900


r


.... 00 I-';


I


I


1540n








type olefins, respectively. There is no explanation, at present,

as to the origin or meaning of this peak.

The data in Table 3 illustrate that an increase in

symmetry has a more pronounced effect on the molar absorptivity

than on the C=C stretching vibration. The values for the

C=C stretching vibrations are in accord with literature average

values (66) of 1657 cm.-1 for cis compounds and 1672 cm.-1

for the trans compounds. The absorption band listed for trans

CH3CH=CHCH3 is probably due to an overtone. The absorption

band listed for trans CH2C1CH=CHCH2C1 probably is due to an

impurity because selection rules prohibit the appearance of

this band in this compound, although forbidden absorption

bands occasionally do appear as weak bands. The trans-4-

methyl-2-pentene configuration must be quite symmetrical since

the hydrocarbon shows only a very weak band and the perfluoro-

compound does not have any C=C absorption band visible even

when the sample is run in a 0.0246 mm. fixed cell as the pure

compound. The octene series C=C absorption bands appear as

expected, except for the trans-4-octene isomer which had a

very weak absorption though none are allowed according to

infrared selection rules, although as stated above, forbidden

absorption bands occasionally do appear as weak bands. Therefore,

the absorption probably is due either to some overtone or slight

impurity.

Substitution, one or more carbon atoms away from a C=C,

has little or no effect upon the C=C stretching frequency as

is verified by the values listed in Table 4. An interesting


















* .
co Co
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H 0 00co o 00
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c0 c0 c0 0 c0 C0 c0 c0
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(d
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cu cd w0
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m co aC
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tl ,. 0,1 U: v v
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m c m c o





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trend is found in the values of the molar absorptivities, for

here substitution two carbon atoms away decreases the C=C

absorption intensity. As the substituted atom is removed from

the C=C the intensity rises until there is a separation of

four carbon atoms. At this point the intensity of the C=C

absorption attains the value of the unsubstituted analog.

No explanation has been offered for this behavior.

Fluorine has a very pronounced effect on the C=C

stretching frequency when it is substituted at the C=C bond.

Additional fluorine substitution on the same carbon atom

further increases the C=C stretching vibration. This trend

is indicated in the vibrational frequency values listed in

Table 5. The molar absorptivity also increases greatly when

one or two fluorine atoms;are substituted on the same carbon.

When a third fluorine atom is added the molar absorptivity

decreases greatly and is found to be about one-third the value

of the singly substituted compound.

The increase in molar absorptivity is due to an increase

in the C=C dipole moment when one or two fluorine atoms are

added to the same carbon atom. Addition of fluorine to the second

carbon atom has a tendency to neutralize part of the electrical

effect present across the C=C from the fluorine on the first

carbon atom. This neutralization results in a decrease in the

dipole moment of the C=C with a subsequent decrease in molar

absorptivity.

The C=C stretching frequencies for the substituted

compounds in Tables 6, 7, and 8 have been arranged according












W





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0
CO


































0
u
0<

0























0


-o
*H
U) cl
cl *H co
co 0 l S

Co Co CO LO
co co co

u u > r: Mq M
a p 0 00 '0o

V V F V V V v

0 U CJ 0 0 C0 4 0


C t0 0o o0 H
CO 00 10 U)















t-
N
\0
H
O) Co co co \o
SI co r- v4 c
\0 \0 \o \o \0
Hr r r-H r


H co H
c co co
0o '0 'o
H H H


O)
Cq
LO
\0
r~~


U)

'o
H


O()0
co H
'0





H H


o oo
H 0o




0 H


E m
r- 0
\0 C4l
\0 N-
Hil H














w




4-)
;Us





















H
rl4
O0



r-l




Ei
0
*H






a)



'0

C





a)


p4


rlO


'0 tN


C)













P4



E-i

S -4
E-i






0







'-4







II


00
o
H










CO)
oo














C) S

H '.4 Z '.0 *- -'
C4 0 m C i-i) L
p4 0 4 P 4 0. r. ..4 0

C C04 C C44 C0 C14 C4 C4 4
P4 A4 p4 0 4 | 0 4 W4
u- ) C)i C) Q 0 0 u


ao U) mc
> c > >
LO 00 C 0 C) 0
\0 00 \0 C4 CM4

H H H H H


> m)
%10 0\
i-l i-


O 0 o N H

















co o \0 r- c
Co 00 0 to 0l

rH H -l H H


(c
t--
oo
-l


1:1
H









ra
4-J


r- Co
ON 0
r- rt


0' 00



r- r-
S No


o co

00
rH H









to decreasing solution frequency values. A study of the compounds

listed reveals a general decrease in the electronegativity as

the vibrational frequencies decrease. Figure 6 is a plot of the

C=C stretching frequency versus the Pauling electronegativity

value of the substituted atom. As is shown in the figure there

is a linear relationship between the electronegativity, according

to the Pauling scale, of the substituted halogen and the C=C

stretching frequency. Except for the tin, mercury, and silicon

substituted ethylenes none of the compounds have substituted

species which have been assigned as electronegativity value.

An attempt was made to plot the frequency values along the lines

of the corresponding series and assign electronegativity values.

However, there was no correlation between the compounds of the

individual series which had identical substituents and their

position with respect to the abscissa representing the Pauling

scale of electronegativities. Therefore, these compounds are

not shown in the figure.

It was noted in Chapter I that in vinyl compounds the

mesomeric effects give rise to only about 4-5 per cent double

bond character (32). According to Halford (12) the vinyl

halides should be mass insensitive. Assuming the remainder of

the intramolecular factors, except for electronegativity, are

minimized or absent, the C=C frequency of vibration should vary

according to the electronegativity of the substituent. That

this is true is shown by' Figure 6. Mass effect is probably the

factor responsible for the high value of the hydrogen substituted

compounds and their failure to lie along the corresponding
















1850





1800
H Cl
I +
OH


> 1750

I +4
0) sl

ba
1700
4 J



1650 +


GH

1600. .4 CF




I I I

1.9 2.1 2.5 2.8 3.0 3.5 4.0

Pauling Electronegativities


Figure 6.--Effect of Substitution at the a Carbon Atom with
Substituents of Varying Electronegativities on the
C=C Stretching Frequency.








lines. The difference, between the experimental value and the

value the compound would have if it fell on the appropriate

line, is approximately 50 cm.-1 for each of the three hydrogen

substituted compounds. This indicates a common cause, which as

stated above, is probably due to mass. The slopes of the lines

of the CH2=CHX and CH2=CXCH2 compounds are approximately the same.

The slope of the CF2=CFX compounds is steeper. This may be due

to the presence of the ionic forms, discussed in Chapter I,

which are believed present in fluoroethylenes and not present in

the other two series of compounds.

The vinyl ethers listed in Table 6 have two C=C absorption

bands. These are due to conjugation with the oxygen atom and

the formation of rotational isomers which are known to be

temperature dependent (76).

Tables 9, 10, and 11 are also arranged so that the

compounds are listed according to decreasing solution C=C

vibrational frequency. The same trends are revealed in these

tables that were found in the previous three tables, i.e.,

as the frequency decreases the electronegativity of the

substituent decreases. Figure 7 shows the linear relationship

obtained when the C=C stretching frequency is plotted against

the Pauling electronegativity. The nitroso compounds were

placed on the line at the positions of their respective C=C

stretching frequencies and indicate an electronegativity value

of approximately 3.17. Since the substituted atom is one

carbon removed from the C=C, the only reasonable explanation

of the substituent's effect upon the C=C would be an inductive

















C44 \0 t 10 0 0

c H H- H c4 C' v '0


*

r
















00
/O3



























o










o














0













0


0






P-4



E-E










E-4
w









03
E-/
o,



CO


E E m ( m m e E
0 0 r- 0 0 O \0 \0 \0 In C
Uf) UO It *7:4 .1 wv
HH r-l r- H H H -i
-' r t r_
%0 0 oO 0 o \o .
N 0l 0 '0 0 0r- l
'0 0 0 0 0 v v

\0









CM4 CO
If) U O a\co 0
\10 C14 cy 0o CO
u 0 0 z e -' C) 0 H
o 0 0 0 0 z C N U U
m C4 C4 C C4 C4 C 4 Cl



9? w w w w 9 ? '14 ? w?
cN C4 N C14 C4 04 Cl cd C4 Cl
^ r 3= r u u 0 0 3
0 0 0 0 0 0 0 0 0


U) o0 C C\h 00 \ 0 \0 \0
v4 U) l 14 *: 4 v' v v
\0 \q q \0 '0 \0 \o0 '0 \0
H HH H H H rH -


O \0 O \ \o
V- .V'

















CO 0

T r41


w


4-J
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S> u
H C + r4


or
0
CO







CD










I
0









co
C









4J
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(1



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t,
<-


d<


co co r
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\o \o \0 'o
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v0
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0 0 o H 0LO
c 'o o r, oo t,:
Co co? cJ 4t o 0 4














o o \o U) U) H- U)
0o o to Co )o %o to
1, c' CO CO mO CO C14
rl -H H H H H r

0












00 H LO U) U to C14 '0
co v 10 \0 10 %0 '0 \0 \0
H H r-H H HrH



H
0


'0
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I



+





Sm s m c

+ U U o 3
C1 4 K3 (M
C M )S I




ci C4 M Co M
Zc cli Z mc uC CM X C EC CM 14



C5 C9 C1 -4 v.
C'/ C"J CNI-' '-' CO C14 C4 C4 C Cl C
9? 9? 9? ~d X 9? U 9?U 9
V V C'I C U C'4 C' v C4


\0 '0
H H-
^-S
\0
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0

0
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a













w


4-)


C H 4-)


*0





0







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-U)













0












0
0


a)
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60 H
0 r%-



\0 \0 \0
5H H HH
r~-
\0
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C14 C4 Ci 0
%0 0 \0 \0



U) V) to \0
\0 \0 \0 H
H r-H H -


to z

Z \ H 0 o -4 i1n
u 0 u 0 z cq~ in C
Ue) cq C\ C C4

U" -d UC U
U) Uo Um U) U) U Y) Uco




C14 C4~ C14 C4 Clj Cl 4
0 0 C U u u
0 vv v 0 0 0 I H


C/)
z









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0
















0) U)




C
U)










0
E-1
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?i
Q


H- U 00 00 m 4 I U) Q\ U)
H U; O\ co U) Q\ U)
co N H H H H '4 H r










Ln\
\0\\0


\0o







r-q
Hl U) 0' N~ N~ Nz N v
to \0 If) to to to to to '



\0






r-i




to


0
O
0








53










w





Ho oo o o 00 %0 o H 0o
0) At O 0c) CO CO co cV) LI)
0
co
















o
.r c C. O 0) N4) 0 V %






O














4J \0 LO 0 00 o 0 Go rN cO
c
0
0








o oo co C1o oo 0 a N oo o Ci Hi 0'
C) Vo U) ) If) in 0 0' Co 0' Co Co S















0 P rH 4w 0 r







u u u uuu u 0 G


C)
z
W
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0
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0
0









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E-
1-1







E-










C3
C)





54







1800-

CF2! CFCF2
F-
1775 Cl- NO-
B Br
'I-
SCF2= CHCF2
F-
1750
CCl
,x I -- I- Br
1725+

o 1675_


4U 1650C--12:iH' ,, C :+- X
B r- C1 CH2= CCH
W :OH

-_- Br CI CH2=CHCH2CH2X
S-
1625.


1600

2.1 2.5 2.8 3.0 3.5 4.0
Pauling Electronegativities
Figure 7.--Effect of Substitution at the p and at the y Carbon
Atom with Substituents of Varying Electronegativities
on the C--C Stretching Frequency.








one. The slopes of all four of the propene series have the same

value and are not as steep as those of the previous series. Once

again the hydrogen substituted compounds are found above the line

and the cause is again believed to be mass effect. The position

of the hydrogen substituted compound for the CH2=CHCH2X series

is 12 cm.-I high. The hydrogen substituted compound for the

CH2=C(CH3)CH2X series is 6 cm.-1 high. The hydrogen in the

CH2=CHCH2X series is one unit of a total of 16 mass units

attached to the C=C as compared to the CH2=C(CH3)CH2X series

where the hydrogen is one unit of a total of 30 mass units.

It is reasonable that the mass effect results in a larger

deviation for the CH2=CHCH2X series than in the CH2-C(CH3)CH2X.

The plot of some substituted 1-butenes is also shown in Figure 7.

In this case the substitutent is too far removed from the C=C

to cause any effect at all and the plot is a horizontal straight

line indicating constant C=C stretching frequency.

Table 12 lists the C=C stretching frequencies of some

fluorine unsaturated compounds. The first five compounds in

this table contain the CF2=CFCH- group and have a strong band

between 1803 to 1797 cm.-1. These values agree with Haszeldine's

statement (57) that terminal fluoronated olefins absorb at

1799 cm.1.

The sixth to tenth compounds listed in Table 12 contain

the CF2=CFCR2- group in which at least one R represents some

atom or group more electronegative than hydrogen. This set of

compounds has a C=C absorption between 1793 to 1785 cm.-1. The

first compound on the second sheet of Table 12 has two C=C

















>

0r 4 +J O OC% m
C' I N a CI)












0.0 0 00


0
CJ)
E-v










C()
ol











H






P 0 H-

0 0









S)C






C) N4


0 co

C) Z oo0 c H
0 C) C O m) Co




C4 C) C4 C) 0 C) 0
W O 4 C W 0 0








57






oH


*\ H
r N S

oz
0










O
0
4P o0\ N
co co







Erl

ri

uuo



a o o 00



c\o \o
C) H H





mIm >m a,
co
Q 0 CO0 'C


I-I C l)

6 00 00 0 0
i-o \ o \ o \ o to o
HH H H H H H-










0 N



0O 0 ul
w 00

0w

C1 C O O


0 0 O Q 0 0
'-S CO C 0 0 P ( 0


<'' 0 0 0
0 II II CC C 0 0
0 0 0 co 0 0 0
O CO CO co CO co
0 0 0 U-' 0 0 0








absorption peaks. Since this compound may have geometric cis-trans

isomers, the peak at 1791 cm.-l is ascribed to the trans form

and the peak at 1776 cm.- to the cis form. The rest of the

compounds did not fit any specific group and are listed in no

particular manner.

The cyclic compounds listed in Table 13 fall into three

categories: hydrogen containing cyclics, chlorine and fluorine

containing cyclics, and fluorine cyclics. The C=C stretching

frequency for the cyclopropenes agree with the values put forth

by Breslow and Peterson (17), Doering and Mole (18), and

Closs and Closs (16). The hydrocarbon cyclic monoolefins C=C

stretching frequencies agree quite well with the values mentioned

in Chapter I. Attention is also called to the trend of increasing

frequency with increased ring size for the hydrocarbon cyclics.

The chlorine and fluorine containing cyclics have approximately

the same C=C frequency of vibration for the C4 and C5 cyclics,

with the C6 cyclic frequency occurring at a slightly lower value.

The increase in the C=C stretching vibration of the perfluoro-

cyclobutene over the perfluorocyclopentene is believed to be

due to some interaction of the C=C stretching frequency with the

C-F bending frequency.

Table 14 list the C=C stretching frequencies of terminal

dienes. It is assumed that coupling is the reason for the high

CH2=C=CH2 vibrational frequency. Conjugation explains the single

peak at lower energies in butadiene. The table reveals that

if two CH2 groups separate two C=C groups then each C=C behaves

like a terminal monoolefin with the result that the C=C absorption

band is approximately doubled compared to the monoolefins.
















4- *

io *i -H
-- 4J

z <
0







O:






0


H
HO
I Uo
U3





01
u

*r




0
C)





0















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!-1a


o00 Co
















4 co H H 00 H
H 0 \0 %0 0 coN 0
H H H H H r-
\r


H i 0 11 Co H0 Co -I H 0 H
C '.o r-o LO LI) miO o o Co
O i) \0 \0 \0 \0 \0 \C \0
H H H H H H H H H


Sv00 v

HO ^s,^


0
O




0
0)



CO











1:4
CO





C)


o 9

H













Co4


rl

LI) H
00
Hl


CM
o
C\)


CN


oc

U-
C)
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S0- u UI-
\.0 0' Co4
C14 C" C4
LO LO C [j





C0 0 C )
0 0 H3-4
C) CI) C)
LI LI n ) Z V O
oJ g
'.0UU '.0















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S;-.



Hco


















I r.H
1 4-
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S
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0















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>>







































oX


0 -
P4

JC4L CJI-


C\JI>'


0o If t

r-q Cr4 ('



















cq CO c0















o \0
C0 0N N0








\0 r

so-
H H
CVLI)
rlcvN









CJC\N
C~l~H


o
cu







r(



0)

4->
*Hl
1-1








61







4-
HE
i o LO l
4 C) N C) H4 C0 00

0 4 H C14
o s










0
c'H C H CO Co C CO
4-' U' ) CO v 4 ^f
;j % i \o \o
S rH H H H H H
CO
U) r-)









S O cw
al q71 00 w v
C) '.0 U') \0 \0 '0 '. '0
HI i H H H H
C I I I
0 LO 0 In C
'H '.0 N '0 .0
oo 0 U) LV) LO L LO
S> U) 0 \0 \0 \0
LOO 1I C00


o 11 0
S C V S
W 0^0


N Q)
a' .0 E
SH H 4





0



u C)
III 4J





0 U
0K
0 0






M II II I IM

C4 C M C M C C' C') 0
M 0 CM 0 0 SC,0
ffi S s a a
II1 -' C. C) _5 C- 0 <_ (








The stretching frequencies of some conjugated C=C

compounds are tabulated in Table 15 for the pure compounds

and in Table 16 for the carbon tetrachloride solutions. The

C=C stretching absorption for 1,3-butadiene and 1,3-hexachloro-

butadiene agree very well with the values given by Haszeldine (57).

Isoprene and compounds containing an isoprene type structure

have strong C=C absorption band at 1597 cm.-1 and a weak band

at 1640 cm.-l which appear consistently. Even though the

compound contains a conjugated system there is only a single

absorption band which appears for (CH3)2C=CHCH=C(CH3)2 at a

frequency of 1622 cm.-l. A series of 1,3-hydrocarbondienes

consisting of the C5, C7, C9, and C12 members gave very consistent

C=C stretching frequencies. The samples were mixtures of the

cis-trans forms of these dienes and their absorption spectra are

illustrated in Figures 8 and 9. Attention is called to the fact

that the perfluoronated 1,3-pentadiene shows only one band at a

higher frequency.

Using the values recorded by Rasmussen and Brattain (78)

and using the frequency values from solutions the absorption

bands for the 1,3-hydrocarbondienes at 1657 cm.-1 and 1603 cm.-1

can be assigned to the trans form and the bands at 1651 cm.-l and

1593 cm.-1 to the cis form. No attempt will be made to assign

the band occurring at 1645 cm.-.

Nasich and Post (86) give the C=C stretching vibration

of allyl silane as 1639 cm.-. Table 17 list the C=C vibrational

frequencies observed for various olefinic silanes. The vinyl

group has an absorption band at 1595 t2 cm.-1, the allyl C=C























CO \O

HN
\0 \o









1 r-i
\o \o





rr'
>* C
Lo o\


-\

v0
H

000



H


m U
10 0

H Hr-


Cl U) 0' Co H H 'o U)
H 0 0' C0 H 0 Co Co
\0 0o U) r- 0 0o \0o \o
H r- H H- l H H H







Co H Co 0' H H lv
r-I H H H- H H


0

0
0







uE
PrL





0





LI

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r--3
i i







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Ii
0


H





01











































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0

0


CO)
C%
UI)
00

H





Co
00
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Lr)


rlz
'U










m cr
H *
(0 0 0*iC.
C CM CM C I
K 0

) C 0 O 0 D
I II II Co




C c Cl Cq r-4 C C

0 0 0 U 0 0 u
Jia m n 1 1 o c
SC00 0 K L -


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v 9
CO Cl
0 0






0 0.
0 0




0 x


CO o


Co 9I
cq
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C14 C'4
ril
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NC*4


0 0
0 0



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S0 '0

































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CI (_) 0-C


CO II II


Vl) VI)
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Sco o a0 11
0 0 Co 0 0
'.0 '0 \.0 \0 \0
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U)
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00 CM l41 :v
rN \o0 \o0 \o0 o
H r-H H H r- H H

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Cl

cl Co I I Co) Co
1-1 z C114
Co' Q 0 Z 0 0
cl C-4 0 j

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0 U 0- 0 O


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cz
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cz







65


















E H CO r- N r- C4 r-l U O
U C' cli LO \0 0 CO 0 0 0
U \o0 o ID U) 1O r- U) \o
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CO
0 C 00 C
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N N 'r- \0 \0 N N \0
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9:) -I
w








0 I
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u







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S ( C' II C Q QV u Z




S pJ-J 0u
0 0 0 0 0 0 0 0 0 0 0



























C0
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o0 C
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o0 o o0 Co 0 U V
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SC T
CM CO II Co


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67





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cd
co






Cl
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c'
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60
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co
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cn~
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0

Nq O CN14


C40 cq- m 0

U)~ U) 0)
co Cc4 NO C-
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U) U) 0) 0n cu N c



C4 C4 C+ C4
i 0 0 0 0
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69











CO \ CO C\ C ON m m Ho c NO
C' ^ Ca r GO LO \O O\ O\
H -- Hl H


















LO oU rrl rOi N C4 l
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0

0

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E-1




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l-l
















4J
03> 0 0 00 0 \Q z
ns *H 0 0o LO CO \O \0
rP J H H H o

O
0












0
*H H- 00 00 00 00
4- co CO Co Co co
S\ \0 \0 \0 0\0
H H H H H r-H H
CO











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0
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U)C CU) ) M S U)



m
S C 0 0 CD co
O co co q44 I 4 4
















C4



U) CO

r f o )H c
-r-4 -, ~
0 C4 C4 Vc) C\4
Z^ 00 0 '0 0 C



0 U 0 -
3 C Cl Cl) *H C) Z
o Z CM CM MJ CM C _)

S H~ Cl cMi CM CM *j
o cl) c n Cl
00 00 0 C
C co co co co 0
S CM



c1 C4 c- C1 C4 1 1
SC4


0
4-1


CI

IH


0


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0



C,























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0
o

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rl
CU






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rC
o








absorbs at 1632 cm. and the methallyl C=C absorbs at 1640 cm.-

One.butenyl group was run and the C=C absorption appeared at

1643 cm.-1

Some unsaturated compounds of tin and phosphorus are

listed in Table 18. The tin compounds indicate the same

consistency of C=C vibrational frequencies as with the silanes

of the previous table, but at a lower frequency. Vinyl diphenyl

phosphine shows no absorption band.

Table 19 list the C=C stretching vibrations of some

oxazines. The C=C vibrational frequencies of the following

cyclic configurations may now be assigned with certainty;

CH2CH=CHCH20N- absorbs at 1663 cm.-, CF2CF=CHCH20N- absorbs

at 1719 cm.-1, and CF2CH=CFCH2ON- absorbs at 1722 cm.-1.













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~N e- 1) 1-1
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.0 C .0
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1-11 I-N I-
c ) C) cq ) '4
cu U )1 U ) rN '. C

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TABLE 19

C=C STRETCHING BANDS OF SOME OXAZINES
FROM THE PURE COMPOUNDS


Compound Frequency in cm.-


CF3NOCH2CH=CHCH2 1663vw

(CF3)2CFNOCH2CH=CHCH2 1663vw


CF2C1CF2NOCH2CH=CHCH2 1662vw

CF3NOCH2CH=CFCF2 1719s

(CF3)2CFNOCH2CH=CFCF2 1719s

CF2C1CF2NOCH2CH=CFCF2 1719s

CF3CFC1NOCH2CH=CFCF 1719s

CF2C1CFC1iNOCH2CH=CFCF2 1719s

CF3CCl2NOCH2CH=CFCF 1719s

CF2C1CF2NOCH2CF=CHCF2 1722s
CF3CFCNOCH2CFCHCF2 1722s

CF2CCFCLNOCH2CF=CHCF2 1722s

CF3CCFCNOCH2CF=CHCF2 1722s
CF3CC12"OCH2CF=CHCF2 1722S
I I















CHAPTER IV

SUMMARY


In this study, the infrared spectra of various C=C

stretching bands were investigated with regard to position and

intensity. The region of interest was limited to the 2000 to

1400 cm.-l range which includes the C=C stretching vibrations of

fluorinated unsaturated compounds as well as of the unsaturated

hydrocarbons.

The spectra of all compounds were determined from the

pure compounds, and whenever possible, from their carbon

tetrachloride solutions.

Two types of olefins were examined in this study.

The data which were obtained demonstrated the insensitivity of

the C=C stretching frequency to the mass effect of increased

alkyl chains whenever the mass was greater than 12. The

frequencies for the carbon tetrachloride solution of the

compounds were 1643 2 cm.-1 for the CH2=CHR series and 1651 1 cm.-l

for the CH2=C(CH3)R series.

A study of a few series of substituted ethylenes and

propylenes showed that the C=C stretching frequency increased or

decreased according to an increase or decrease in electronegativity

of the substituent. A plot of C=C stretching frequencies versus

74






75


halogen electronegativities, according to Pauling's scale,

for the halogen substituted compounds resulted in a linear

relation.

The absorption characteristics of some fluorine

unsaturated compounds, cyclic monoolefins, conjugated dienes,

silanes, and oxazines were also examined. Some trends in the

frequency shift as well as changes in the molar absorptivity

were noted. Some frequencies were definitely assigned.















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BIOGRAPHICAL NOTE


Leon S. Pijanowski, Jr. was born April 29, 1931, at

Philadelphia, Pennsylvania, and received his early education

in the parochial schools of that city. He graduated from

La Salle High School, Philadelphia, Pennsylvania, in June, 1949.

He studied at Villanova University from September,

1949, until he entered the United States Navy in March, 1951.

He was honorably discharged from the United States Navy in

February, 1955, and returned to Villanova University to complete

studies for the Bachelor of Science degree. He graduated in

June, 1958.

Graduate studies were undertaken at the University

of Florida in September, 1958. While a graduate student, he

was employed as Graduate Assistant in the Department of Chemistry.

In September, 1960, he was awarded a General Motors Fellowship.

He is a member of Alpha Chi Sigma Chemical Fraternity and

of the American Chemical Society.














This dissertation was prepared under the direction of

the chairman of the candidate's supervisory committee and has

been approved by all members of that committee. It was submitted

to the Dean of the College of Arts and Sciences and to the Graduate

Council, and was approved as partial fulfillment of the requirements

for the degree of Doctor of Philosophy.



April 20, 1963




Dean, College of Arts and Sciences




Dean, Graduate School


Supervisory Committee:



/ Chai





S/ /












4









4

UNIVERSITY OF FLORIDA
3 1262 08553 5218





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