A ttudy of Certain i-nitrostyrenes mFnctionally Capable
of Independent Anioaic and Catioaic Initiation
JA2MES WESLEY SC 7L, iERT
A DIS3-:% \TION ?'-:.'-:IED TO THE GRADUATE COUNCIL OF
THE UjIVERSIT-l' OF FLORIDA IN ?ARCI&,
FULFILTLENT OF THE !iEQ7r. :.t~.:. FOR THE DEhGREE OF
D'.C :. OF PHILOSOPHY
'J li'Y OF FLOr.'.\'
The author wishes to express his deep appreciation and gratitude
for the encouragement and guidance provided by his research director,
Prof. George B. Butler. Suggestions and comments by other members of
his supervisory committee as well as Dr. Thieo Hogen-Esch were also
The author's wife, Rose, has been of inestimable value toward
the completion of this work. Her continued love and devotion despite
months of neglect is very gratefully acknowledged. Her patience, moral
support and typing of this dissertation were also appreciated .
Fellow students in this laboratory have made the author's work
atmosphere a very pleasant one and their friendship and advice are
appreciated. Many helpful discussions with Dr. Kiyo Fuji-noi and Dr.
Bruno Zeegers have been particularly rewarding.
TABLE OF C'i:;i,..rS
S"OV l D( E:JTS ..................................................... ii
LIST OF TABLES ................................................ v
LIST OF FIGURES ............... ................................. vi
ABSTRACT ......... .. .............................................. viii
I INTRODUCTION .......................................... 1
Background ................................ ........... 1
General Background ............... ............... .. 1
Synthesis and Chemistry of the (2-vinyloxy-3-
nitrostyrenes .................................... 2
The Effect of Meta and Para-substituents on the
Anionic Polymerization of S-nitrcstyrenes ......... 6
Effect of Ortho-substituents on the Rate of Polymer-
ization on the Anionic Polymerization of 3-nitrostyrenes 7
Objectives of This Study ............................. 8
Chemistry and Polymarization of (2-vinyloxy)ethoxy-
K-nitrostyrenes ................................... 8
Effect of Meta and Para-substituents on the Rate of
Anionic Polymerizations of Certait 3-nitrostyrenes 12
II EXPERIMENTAL ......................................... 17
Synthesis and Chemistry of Ortho- Meta- and Para-
(2-vinyloxy) t-thoxy-S-nitrostyrenes ................... 17
Preparation of the (2-vinyloxy)etho:-y-substituted
-nitrostyenes ..................................... 17
Cationic Polymerization Studies of the (2-vinyloxy)-
ethoxy-substituted -nitrostyrenes ................. 24
Anionic Polymerization Studies of (2-vinyloxy)ethoxy-
substituted $-nitrostyrenes ....................... 26
Analysis of the Confromation of Para-(2-v-nyloxy)-
ethoxy--nitrostyrene ................. ........... 28
Studies of the Anionic Polymerization of Some Mono-
substituted -nitrostyrenes ..... .................... 30
Synthesis of Substituted 3-nitrostyrenes .......... 30
Determination of the Rate of Propagation in the
Anionic Polymerization of Certain MetaT and Para-
substituted 8-nitrostyrenes and B-nitrostyrene .... 34
Determination of the Rate of Initiation of Two
Representative Monomers, Para-methoxy-3-nitrostyrene
and P-nitrostyrene ............................... 36
Effect of Changes in Initiator Concentration on the
Rate of Anionic Polymerization of 5-nitrostyrene .. 40
Determination of the Molecular Weight Distribution
Curves of Some Representative Monosubstituted Poly-
B-nitrostyrenes .................................. 41
The Role and Mechanism of Initiation and Termination
in the Anionic Polymerization of Meta and Para,B-
dinitrostyrene ................ ..... ................ 42
Studies of Certain Aspects of the Ortho-effect ....... 49
Instruments Used .............................. ....... 54
Source and Methods of Purification of Reagents ....... 55
III RESULTS AND DISCUSSION ............................... 57
Synthesis and Chemistry of Ortho, Meta, and Para-
(2-vinyloxy)ethoxy-8-nitrostyrenes ................... 57
Preparation of the Monomers ....................... 57
Cationic Polymerizations of Ortho, Meta, and Para-
(2-vinyloxy)ethoxy-3-nitrostyrene ................. 58
Anionic Polymerizations of Ortho, Meta, and Para-
(2-vinyloxy)ethoxy-P-nitrostyrene ................ 58
The Possible Existence of an Intramolecular Interaction
and Six-membered Ring Formation by Para-(2-vinyloxy)-
ethoxy-$-nitrostyrene ............................. 59
Studies of the Anionic Polymerization of Some Other
MXno-substituted 3-nitrostyrenes .................... 68
Synthesis of Compounds ............................ 68
Kinctic Study of the Polymerization Rates ......... 69
The Mechanism of Termination in the Anionic Polymer-
izatiun of Meta and Para,8-dinitrostyrene ......... 98
The Ortho-effect .................................. 103
BIBLIOGRAPHY ...................................................... .... 112
BIOGRAPHICAL SKETCH ......................................... 115
LIST OF TABLES
1. Kinetic Data of Propagation Reactions 37
2. Kinetic Data for Changing Initiator Concentrations 41
3. The Effect of Initiator Ion on Polymer Yields 50
4. Kinetic Data of the Anionic Polymerization of Ortho-
5. Pertinent Infra-red Data of Monomers, Polymers, and
Related Compounds 62
6a. Nuclear Magnetic Resonance Data from Some Vinyloxy
6b. Nuclear Magnetic Resonance Data from Some Vinyl Ethers 63
7. Results of Molecular Weight Distribution Analysis of
Some Poly--nitrostyrenes by Gel Permeation C~lcrongraphy
8. Elemental Analyses of Poly-E-nitrostyrenes 71
9. Thermal Behavior of Poly-substituted-i-nitrostyrenes 72
10. Propagation Rate Constants (k ) 88
LIST OF FIGURES
nitrostyrene by Sodium Ethoxide
Kinetics of the Rate of Initiation of F
Molecular Weight Distribution Curve of
Kinetics of the Anionic Polymerizations
Kinetics of the Anionic Polymerization
Kinetics of the Anionic Polymerization
Kinetics of the Anionic Polymerization
Kinetics of the Anionic Polymerization
Kinetics of the Anionic Polymerization
Kinetics of the Anionic Polymerization
Kinetics of the Anionic Polymerization
Kinetics of the Anionic Polymerization
1. MIR Spectrum of Ortho-(2-vinyloxy)ethoxy-~-nitrostyrene
2. NMR Spectrum of Meta-(2-vinyloxy)ethoxy-B-nitrostyrene
3. :]*P Spectrum of Para-(2-vinyloxy)ethoxy-8-nitrostyrene
4. Major Infra-red Absorptions of 1-chloroethyl Vinyl Ether,
Para-nitro-(2-vinyloxy)ethoxybenzene, and Para-(2-vinyloxy)-
5. The Ultra-violet Spectra of Para-(2-vinyloxy)ethoxy-a-
nitrostyrene and the Cationically Initiated Polymer of
That Compound (Methylene Chloride)
6. Kinetics of the Rate of Initiation of Para-methoxy-8-
18. Kinetics of the Anionic Polymerization of Meta, -
19. Effect of Changes in the Concentration of Initiator on
the Rate of Anionic Polymerization of -nitrostyrene 90
20. Correlation of the Relative Rates of Anionic Polymer-
ization of (-nitrostyrenes with a 91
21. Correlation of the Data of Kamlet and Glover for the
Relative Rates of Michael Addition of Barbituric Acid to
(-nitrostyrenes with a 92
22. Correlation of the Data of Kamlet and Glover for the
Relative Rates of the Mic ael Addition of Barbituric Acid
to $-nitrostyrenes with a 99
23. Correlation of the Relati e Rates of Anionic Polymerization
of B-nitrostyrenes with a 100
24. The Molecular Weight Distribution Curve of Poly-meta-
25. Kinetics of the Anionic Polymerization of Ortho-fluoro-
26. The Reactivity of Ortho-fluoro-8-nitrostyrene with
Sodium Ethoxide 106
27. The Reactivity of Ortho-chloro-@-nitrostyrene with Excess
Sodium Ethoxide 107
28. The Reactivity of Ortho-bromo-B-nitrostyrene with Excess
Sodium Ethoxide 108
29. The Reactivity of Ortho-methoxy-$-nitrostyrene with
Excess Sodium Ethoxide 109
30. The Reactivity of Ortho(2-vinyloxy)ethoxy-3-nitrostyrene
with Excess Sodium Ethoxide 110
Abstract of Dissertation Presented to the
Graduate Council of the University of Florida in Partial Fulfillment
of the Requirements for the Dagree of Doctor of Philosophy
A STUDY OF CERTAIN BETA-NITROSTYRiENES FLr.U:CEO:l\LLY CAPABLE
OF I;n:iPEND.DNT ANlO.AC AND CATIONIC INITIATION
James Wesley Schwietert
Chairman: G. B. Butler
Major Department: Chemistry
The purpose of this work was to synthesize and polymerize a
set of ideal cross-linking monomers which could be selectively polymer-
ized through one vinylic moeity to a linear soluble polymer followed
by selective cross-linking via another pendant vinylic moeity. A study
was also initiated to determine the effect of various substituents on
the anionic polymerizations of various beta-nitrostyrenes. A study of
ortho-substituted beta-nitrostyrenes, which had been previously reported
to be rcsiscant to anionic polymerization, was also initiated.
The three isomers of (2-vinylo:xy)ethoxy-beta-n.itrostyrene have
bean synthesized and found to selectively polymerize anionically through
the nitrovinyl moeity upon reaction with an alkoxide. They have also
been found to selectively polymerize cationically through the vinyloxy
group upon reaction with a Lewis acid.
A kinetic study of the anionic polymerization of beta-st, rc.nes
has been conducted using a gravimetric method and the relative rates of
propagation unexpectedly found to correlate well with Brown's sigma
values. The -rates of initiation of two monomers with sodiurm ethoxide
have been found to be rapid. The i-ate of chain transfer in ethanol ha-
been studied qualitatively using gel permeation chromatography to obtain
molecular weight distribution curves. The low values of the ratios of
weight-average molecular weight to number-average molecular weight indi-
cate little chain transfer in the protic solvent.
All ortho-substituted beta-nitrostyrenes except the ortho-fluoro
compound have been found to be resistant to anionic polymerization. This
phenomenon has been unambiguously shown to be the result of inhibition
of propagation and not initiation.
A. General Background
-nitrostyrene was probably first polymerized anionically by
Priebs who was studying the effect of alkalies on the compound. He
reported obtaining amorphous products. The polymerizations of some
a-nitrostyranes have been studied to some extent ''4 but the mechanism
has not been examined in detail nor have many properties of the poly-
mers been studied. This fact is primarily due to the poor solubility
of the polymers in common organic solvents.
The solubility problem not only prevents spectroscopic analysis
of the polymerization reaction but prohibits molecular weight dctermi-
nation as well as determination of other properties of the polymers.
In earlier work, Butler succeeded in determining the molecular weights
of some samples of poly-.-nitrostyrene by an ebullioscopic method in
butanone. He also made .the interesting observation that poly-B-nitro-
styrene apparently underwent depolymerization after being heated in
dimethylfornamide as evidenced by lower molecular weights. Other
substituted poly-I-nitrcstyrenes were reported insoluble in all solvents
The apparent ease with which 3-nitrostyrene anionically poly-
merizes is principally due to the strong electron withdrawing
capability of the nitro group, both by inductive and resonance effects.
This makes the vinylic double-bond, in general, electron deficient and
the a-carbon, in particular, vulnerable to nucleophilic attack. For
the same reasons the compound appears to be resistant to cationic and
free radical polymerizations.
On the other hand, the electron-rich vinyl ethers have been
found to be very susceptible to electrophilic attack by Lewis or
Bronsted acids. This attack may lead to hydrolysis of the ether in the
presence of water or polymerization under anhydrous conditions.'
At the same time, vinyl ethers have been found to be quite resistant to
B. Synthesis and Chemistry of the (2-vinyloxy)ethcxy-$-nitrostyrenes
This wide variation in reactivity between the two types of
vinyl groups makes them ideal functional groups for two-stage polymer-
izations. It was with this goal in mind that Nash" attempted to syn-
thesize ortho- metaT and para-(2-vinyloxy)ethoxy-$-nitrostyrene.
H 2 _V O-CH2CH2-0-CH=CH2
The method of synthesis requires first reacting the potassium
salt of the corresponding hydroxybenzaldehyde with B-chloroethyl vinyl
ether (Williamson synthesis) to form a (2-vinyloxy)etho:;ybenzaldehyde.
The benzaldehyde is then condensed with nitromethane with an equimolar
amount of potassium hydroxide to form a salt which upon acidification
yields the desired f-nitrostyrene. This latter reaction was first
reported by Thiele.
(1) CH NO
+ Cl-CH-CH -O-CH=CH2--+ KOH
+ (2) HC1
O K O-CH CH2 O-CHCCH2
1 2 2
During Nash's study, he found that the meta and para isomers
polymerized readily in the presence of sodium methoxide. He also
noted that these monomers lacked the 1202 cm infra-red absorption
typical of vinyl ethers. These monomers were found to be resistant
to cationic polymerization upon reaction with BF3 Et20. Nash con-
cluded that the two-stage polymerizations were "impractical" due to
the apparent reluctance of the vinyloxy groups to cationically poly-
Thompson considered two possible explanations for the appar-
ent lack of reactivity toward electrophilic attack displayed by the
vinyl ether group on the para isomer. The first possibility he con-
sidered was an inductive effect. The resonance between the electron-
withdrawing nitro and the phenolic oxygen should lead to a signifi-
cant degree of positive charge on the oxygen due to the following
contributing resonance form:
+ N=C\ +
-0 HC= =0-CHRCH2-O-CH=CH2
Electrophilic attack dn the 0-carbon of the vinyl ether would
produce a carbonium ion on the a-carbon which, in turn, would rely on
the lone-pair electrons on oxygen for resonance stabilization.
/ C= 0 -CH2CH2- =CH-CH2-E
Consequently, the two contributing resonance forms would involve oxo-
nium ions separated by a two-carbon saturated hydrocarbon bridge. The
other possibility considered involved an intramolecular interaction
between the terminal methylene of the vinyloxy group and the phenolic
+N=C ~ CH- CH
H -- CH-CH2
In considering the inductive factor, Thompson pointed out chat
the pKa of chloroacetic acid is 2.86 while that of p-chloropropionic
acid is 4.00. The pKa of acetic acid is 4.80. This "quite minor"
difference was considered to be evidence against th2 inductive effect.
Thompson then carried out an extensive and systematic study
of the physical and spectral properties of the (2-vinyloxy)ethoxy-
(-nitrostyrenes and related cormpou-ids in search of evidence. During
this study, he clearly demonstrated that Nash's method of synthesis,
which involved generation and precipitation of the (2-vinyloxy)ethoxy-
3-nitrostyrene in excess dilute hydrochloric acid, resulted in the
quantitative acid catalyzed hydrolysis of the vinyl ether group to the
corresponding alcohol. Thompson modified the method of synthesis by
lower lg the reaction temperature and using only a slight excess of
acid. Using these modifications, he successfully synthesized the ortho
and para isomers, although he was unsuccessful in isolating the meta
Thompson's spectral study included comparison of the ultra-
violet spectra of para-(2-ethyloxy)ethoxy-$-nitrostyrene with the
corresponding vinyl ether. Thompson observed no indication of an in-
tramolecular interaction with those data.
Shostakovskii postulated a mesomeric effect for vinyl ethers
between the vinylic i-orbital and a lone-pair p-orbital on the oxygen.
Since there are two such lone-pairs, such an effect would be expected
to lead to rotational isomerism. Brey and Tarrant4 observed 2 absorp-
tions in the 1600-1650 cm-1 region for vinyl ethers and attributed
this to the existence of two rotational isomers.
Thompson pointed out that only one such rotational isomer
would be present if the postulated intramolecular electrostatic attrac-
tion resulted in C being the sole existing conformation of the com-
pound. He then obtained an infra-red spectrum of the compound using
a Perkin-Elmer Model 21 double beam recording spectrophotometer and
observed an absorption at 1621 cm- but no absorption maximum between
1635 and 1660 cm. Vinyl ethers normally possess a second but weaker
absorption at 1640 cm- in addition to the 1620 cm absorption. This
was interpreted as supporting evidence for the intramolecular inter-
He obtained further data for the vinyloxyethoxy series as
opposed to the ethyloxyethoxy series by experimentally determining the
dipole moments in solution of each compound. The dipole moment for
para-(2-vinyloxy)ethoxy-g-nitrostyrene was 5.43 D. as opposed to 6.14
D. for para-(2-ethyloxy)ethoxy-o-nitrostyrene. This difference was
Thompson concluded that his infra-red data indicated that the
ring was the only form present, that his ultra-violet data indicated
that the ring form (C) was probably not present, and that the dipole
moment data indicated that there might be a contribution of the ring
C. The Effect of Meta and Para-substituents on the Anionic Polymerization
Little quantitative work has been done to study the effects
of substituents on the reactions of -nitrostyrenes. Worrall5 found
that 2-nitrostyrene formed adducts with certain primary amines such as
toluidine, phenyl hydrazine, aniline, and para-tolyhydrazine but was
unreactive toward para-bromophenylhydrazine and ortho- and meta-tolui-
dine. He also reportedly6 that para-methyl-?-nitrostyrene, while not
resistant to polymerization, was resistant to attack by all of the
previously mentioned amines. However, nitration of the compound to
meta-nitro-para-methyl-B-nitrostyrene was found to increase the reac-
tivity of the compound. Addition products with aniline and para-tolui-
dine were formed but the compound was still unreactive toward phenyl-
hydrazine. Worrall later reportedly7 that para-N,N-dimethylamino-B-
nitrostyrene was not only resistant to reaction with the more reactive
amines but also resistant to anionic polymerization.
Kamlet8 has reported that barbituric acid reacts with certain
2-nitrostyrenes in neutral or acidic media to form the corresponding
5-(2-nitro-l--aryl)-barbituric acids. The structures of the compounds
thus synthesized were confirmed by oxidative degradation. Kamlet and
Glover later carried out a kinetic study of this reaction in a
buffered solution of dioxane in water. They demonstrated that the
reaction was first order both in barbiturate anion (or barbituric acid)
and 3-nitrostyrene. They then obtained by ultra-violet analysis second
order rate constants for B-nitrostyrene as well as for six substituted
B-nitrostyrenes. A Hammett plot of this data appears in Figure 21.
No analogous study has been carried out to determine the effect
of substituents on the rate of anionic polymerization of B-nitrostyrenes.
Drueke7 polymerized several substituted B-nitrostyrenes under identical
conditions and, for the meta- and para-substituted compounds, observed
no direct correlation between the expected reactivity of the compounds
and the yield of polymer. In fact, he reported that para,B-dinitrosty-
rene, which he expected to be the most reactive of those tested, gave
one of the poorest yiels (7.93 percent conversion). Meta,B-dinitrosty-
rene, also a relatively reactive compound, also gave a poor yield (1.45
percent conversion). Under identical reaction conditions, the much less
reactive para-methoxy-$-nitrostyrene gave 65 percent conversion to etha-
nol insoluble polymer. No explanation was offered.
D, Effect of Ortho-substituents on the Rate of Polymerization on the
Anionic Polymerization of 3-nitrostyrenes
The reactivity of various ortho-substituted B-nitrostyrenes
toward various primary amines has been quite extensively studied by
Worall. He reported20 that ortho-methoxy-B-nitrostyrene was unreactive
toward all amines tested (as was the para isomer). However, nitration
of the compound with fuming nitric acid gave a compound which he
identified (probably incorrectly) as ortho-methoxy-para,B-dinitrostyrene.
This compound reacted with para-toluidine to form a 1:1 adduct.
Ortho-chloro21 and ortho-bromo-8-nitrostyrenes22 were synthesized and
each was also found to be unreactive toward all amines tested. However,
nitration of each produced the corresponding 2-halo-5,3-dinitrostyrene.
Both were observed to be more reactive toward amines than (-nitrostyrene,
giving 1:1 adducts with ortho-, meta-, and para-toluidine. Ortho-
iodo- -nitrostyrene23 was also synthesized and studied. Worall found
that, while the B-nitrostyrene was also unreactive, nitration of the
compound to 2-iodo-5,8-nitrostyrene made the compound apparently more
reactive toward amines than the corresponding chloro and bromo analogs.
There was no apparent "ortho-effect" reported for this type of reaction
and Worall made no coirrents as to the polymericability of these com-
Apparently the first report of an "ortho-effect" was made
when Nash3 found that ortho-allyloxy-$-nitrostyrene and ortho-methoxy-
meta--allyl-S-nitrostyrene both failed to give ethanol insoluble polymer
upon addition of sodium methoxide. Later, Drueke found that ortho-
methoxy-, nitro-, and chloro--3-nitrostyrenes gave no ethanol insoluble
polymers while ortho-fluoro-B-nitrostyrene gave 1.84 percent conversion
to ethanol insoluble polymer. This effect was attributed to steric
factors by that worker.
Objectives of This Study
A. Chemistry and Polymerization of (2-vinyloxy)ethoxy-B-nitrostyrenes
Thompson's successful synthesis of the ortho and meta isomers
and his identification of the products of Nash's intended synthesis of
these compounds suggested that these compounds might be excellent
monomers for two-stage polymerizations. One of the first objectives
of this study was to test these compounds for such behavior. Such a
development could lead to very practical applications. Monomeric
(-nitrostyrenes have been found to be effective in combating bac-
24,25,26,27 24,26,28 29 26,28
teria, fungi, mold, and insects. The vapor pres-
sure and solubility of many monomeric fungicides make them, at least
mildly, hazardous to the environment. However, if such a biologically
active moeity were pendant on a polymer chain of reasonably high mole-
cular weight, it would have the ecological advantage of being essen-
tially immobile. The successful cationic polymerization of any of the
three isomers of the vinyloxyethoxy-g-nitrostyrenes would lead to such
It was also felt that the postulated ring form for the para
isomer was worthy of more study. Despite the fact that Thompson proved
that the para isomer, as synthesized by Nash (with vinyl ether moeity
no longer present), could not have cationically polymerized, his spec-
tral and physical data seemed to indicate that such a form might still
be a contributing form or tha sole form of the compound.
The uncommonly high dipole moment of the compound as determined
by Thompson indicates that there must be a significant amount of posi-
tive charge on the phenolic oxygen. The nmr spectra of vinyl ethers
indicates that there is a significant amount of negative character on
the terminal carbon as evidenced by the relatively high field chemical
shift of the terminal protons. Banwell and Sheppard have attributed
this effect directly to the mesomeric effect since electron donation
through resonance interaction" leads to increased electron density on
the terminal methylene carbon. This is due to the fact that the mag-
netically anistropic T electrons are distributed over 2 bonds rather
Thus with considerable positive charge on the phenolic oxygen
and some degree of negative charge on the terminal methylene, the pos-
tulated 6-membered ring would appear to be a viable possibility.
One of the first objectives of this study was the successful
synthesis of the meta isomer to permit careful comparison of the chem-
ical and physical characteristics of the two compounds. If the induc-
tive effect is the predominant effect on the chemical and physical
behavior of para-(2-vinyloxy)ethoxy-B-nitrostyrene, then one would
expect a decreased mesomeric effect in the para isomer as compared to
the meta isomer. On the other hand, the contribution of the ring form
would be expected to increase the degree of the mesomeric effect rela-
tive to the meta isomer.
Theoretical work by Gutowski, Karplus, and Grant followed
by a systematic nnr study of vinylic compounds by Banwell and Sheppard
has show that the coupling constants, particularly the geminal coup-
ling constant (Jgem), are quite sensitive to inductive effects. The
latter work indicated that in the case of monosubstituted vinylic
compounds, there is a definite correlation between the electronegati-
vity of the substituent and the geminal coupling constants of the
terminal methylene protons and that decreasing coupling constants go
with increasing electronegativity. These findings gave excellent
agreement with theoretical predictions. Geminal coupling constants
for vinyl halides ranged from -3.2 hz. for vinyl fluoride to -1.7 hz.
for vinyl bromide.
Later work by Feeney, Ledwith, and Sutcliffe33 applied this
type of analysis to vinyl ethers. In the case of simple vinyl ethers,
R-0-CH=CH2 2 -> R-&=CH-CH2
the inductive effects of various alkyl groups were expected to exert
an influence on the extent of mesomeric stabilization and, in turn,
on the amount of carbanion character on the terminal methylene. Their
data, which appear in Table 6a, for vinyl ethers- in which the R was
a single saturated alkyl substituent, showed that as the electron
donating (inductive) ability of the substituent increased so did the
geminal coupling constant. The values obtained ranged from Jgem =
-0.1 hz. for t-butyl vinyl ether to Jgem = -2.2 hz. for methyl vinyl
ether. B-chloroethyl vinyl ether was found to have a geminal constant
of -2.7 hz.
The apparent sensitivity of the coupling constants to the
character of the substituents suggested that a detailed nmr study of
the (2-vinyloxy)ethoxy substituted -nitrostyrenes might help clarify
A thorough analysis of the infra-red spectrum of the three
isomers of the (2-vinyloxy)ethoxy-5-nitrostyrenes as well as related
compounds appeared desirable as well. It is interesting to note that
Feeney, Ledwith, and Sutcliffe33 saw no indication of rotational isomer-
ism for 2-ethylhexyl vinyl ether between temperatures of -1000 and 1000
C. in their nmr study in contrast to the infra-red work of Brey and
B. Effect of Meta and Para-substituents on the Rate of Anionic Polymer-
izations of Certain 3-nitrostyrenes
A study was also initiated during the course of this work to
obtain some quantitative data concerning the effect of meta and para-
substituents on the rates of anionic polymerizations of B-nitrostyrenes.
The rates of polymerization were determined by a gravimetric method.
The rates of initiation of two representative monomers were obtained
The process of initiation in an anionic polymerization may be
+ i +
expressed as IA + M -> I-M- A where:
I is the initiating species
A is the counterion or gegnion
M is the monomer
k. is the rate constant of initiation
The over-all rate of initiation mey be expressed in the form
v. = k.[I J[M].
The process of propagation mey be expressed as
-+ k +
R-(M)-"M A + M -2, R-(M) -M A where:
R-(M)-M is the growing polymer molecule
k is the rate constant of propagation
The rate of propagation mey then be expressed as
--d [M1 -
--d -= V = k [M ][M], where M refers to the concentration of actively
dt p p
propagating anions. It was assumed in this study that the above
relationship adequately described the over-all rate of polymerization
of certain mono-substituted g-nitrostyrenes. This required that the
following assumptions be made:
1. The rate of initiation is fast relative to the rate of
2. The rate of chain transfer is small or non-existent
relative to the rate of propagation and, if it does occur, it does not
alter the kinetic chain.
3. Auto-termination does not occur during the polymerization.
4. The length of the polymer chain does not affect the rate
5. The rate of propagation remains essentially unchanged
during both the homogeneous and heterogeneous stages of the polymer-
6. Conversion of initiator to propagating carbanion is quan-
titative and the reactivity of all resulting ion-pairs is assumed to
7. The rate of polymerization equals the rate of disappear
ance of monomer; V = _d~ML = d_(P where P is polymer yield expres-
p dt dt
sed in terms of moles of monomer units/liter of solution. This assump-
tion precludes any significant side-reactions, e.g., the base catalyzed
Michael addition of ethanol to 5-nitrostyrene.
Assumption 7, if valid, permits the rate of polymerization to
be monitored gravimetrically by weighing the precipitated polymer.
This approach, in turn, requires that precipitation of polymeric prod-
uct be essentially quantitative.
The Hammett equation has been used to a limited extent in
mechanistic polymer chemistry. The treatment has been used to study
the free radical polymerization of styrene, cationic polymerizations
of styrenes 7 and phenyl ethers, Ziegler-Natta polymerization of
styrenes, and reaction of polystyryl anions with styrenes.
The Hammett equation was applied to this study using the form
log k /k = ap,where k is the second order propagation rate constant
p o p
of a substituted---nitrostyrene and k is the propagation rate constant
of unsubstituted-L-nitrostyrene. Hammett treatment would permit quan-
titative comparison of the Michael reaction9 and anionic polymeriza-
tion of [-nitrostyrenes. Since the rate-determining step of the
Michael reaction, like anionic polymerization, is said to involve at-
tack of the anion on substrate one might expect similar results.
A kinetic study of the anionic polymerization of the ortho-
substituted-a-nitrostyrenes was also undertaken. It was hoped that
such a study might clarify whether or not the effect observed by Nash13
and Drueke7 was purely steric as well as distinguish between the two
possibilities of steric inhibition of initiation and steric inhibition
A very brief and superficial study was carried out to deter-
mine the extent of chain transfer and/or termination by studying the
molecular weight distributions of some of the representative polymers
obtained during the kinetic studies.
It should be noted that all anionic polymerizations were
carried out in a protic solvent system. In most cases of anionic
polymerization, the presence of a protic co"->po-nd, even in small con-
centration. leads either to termination or chain transfer. Volker42
found that by varying the concentration of methanol, he could vary the
molecular weight of polymer obtained from the anLonic polymerization
of methyl methacrylate. By increasing the concentration of chain
transfer agent (methanol), he could quite precisely lower the molecu-
lar weight of product polymer.
Szarc and coworkers, on the other hand, reported that
anionic polymerization of vinylic compounds which formed "living poly-
mers" led to the formation of polymers having very narrow molecular
weight distributions. These polymerizations were run in scrupulously
dry aprotic solvents under an inert atmosphere or high vacuum.
The molecular weight distribution of a given polymer sample
can be obtained by one of the several known laborious methods of mole-
cular weight fractionation such as ultra-centrifugation, fractional
47 48 49
precipitation, sequential extraction, dialysis, and several others.
The worker then determines the molecular weight of each polymer frac-
tion obtained. The recent advent of practical gel permeation chroma-
tugraphy (GPC), as applied to polymer chemistry, has provided an
analytical, as well as preparative, tool for rapid fractionation and
determination of molecular weight distribution curves.
Briefly, this method separates different molecular weight
polymer molecules on the basis of molecular size. A polymer solution
is passed through a column containing insoluble porous gel particles.
The longer polymer molecules, whose physical size effectively prevents
their diffusion into the gel pores, pass more quickly through the
column by passing between the gel particles with the solvent flow. The
smaller polymer molecules spend more time diffusing in and out of the
gel pores and consequently travel more slowly through the gel. Upon
leaving the column, the fractionated solution passes through an ultra-
violet photometer and/or a differential refractometer. Thus, the
recorded signals from these detectors are molecular weight distribu-
The recorder also records the volume of solvent passing through
the column during a given run in the form of 5 ml. "count" marks. The
volume of solvent required to elute a given polymer size is extremely
characteristic of that size. Thus, a calibration curve derived from
standard polymer samples of known molecular weight and size can be
used to determine number average molecular weights and lengths of a
given polymer sample of the same type polymer, e.g., polystyrene.
Synthesis and Chemistry of Ortho- Mta- and
A. Preparation of the (2-vinyloxy)ethoxy-substituted 3-nitrostyrenes
These compounds were synthesized by the method of Thompson
with some slight modifications in the work-up procedure.
1. Ortho-(2-vinyloxy)ethoxy-.-nitrostyrene.-- The potassium
salt of salicylaldehyde was prepared on a 0.2 mole scale by reacting
24.41 g. of salicylaldehyde (in 20 mis. of absolute ethanol) with 13.20
g. of 85 percent potassium hydroxide dissolved in 140 mls. of absolute
ethanol. The solvent was then removed by distillation under vacuum.
Any remaining water was removed via the benzene-water azeotrope. The
yellow crystalline product was then dried under vacuum for 24 hrs. The
yield was essentially quantitative and the hygroscopic salt was used
The potassium salt was dissolved in 120 mls. of dimethyl-
formamride which had been dried over 4A molecular sieves. To this
solution was added 0.2 mole plus 10 percent excess of --chloroethyl
vinyl ether. The solution was refluxed gently for 24 hrs. with stir-
ring. After the reaction mixture had cooled to room temperature, suf-
ficient deionized water was added to dissolve the precipitated potas-
siun chloride. The product was then extracted with ether and the
ethereal solution was dried with anhydrous m:agnesium sulphate. The
ether was removed by vacuum distillation at room temperature and the
ortho-(2-vinyloxy)ethoxy-benzald..-hiyde was then purified by distilla-
tion (110C. at 0.17mm Hg) yielding 28.8 g. (75 percent yield) of the
light yellow oil. The spectral and physical properties of the product
agreed with thoseof Thompson.
The corresponding -nitrostyrene was synthesized via a modi-
fied Thiele reaction. The compound was synthesized en a 0.113 mole
scale. 21.64 g. of the benzaldehyde were placed in a 250 ml. erlen-
meyer fla;k with 100 mls. of absolute methanol and 6.1 mls. (0.113
mole) of nitromethane. This solution was chilled in an ice-methanol
bath (with magnetic stirring) to -50C. To this solution wa3 added,
dropwise, 22.5 mls. of 5.0 M. potassium hydroxide in water (0.113
mole). The potassium hydroxide solution was added at such a rate that
the temperature was not allowed to e-xceed 00C. The solution was then
stirred at the same temperature for an additional 10 minutes. The
solution was then added to about 30 g. of ice in a 250 ml. separatory
funnel and the ice was allowed to nelt with occasional swirling. The
resulting solution was added drop-'ise to a vigorously stirred mixture
of 75 g. of ice, 100 mls. of water, and 11 mis. of 37 percent HCl
(0.113 mole plus slight excess). Ice was added during this step as
needed to keep the mixture cold. The resulting yellow precipitate
was quickly filtered and washed wLth 500 mis. of chilled dJionized
w.ter to r,.rove excess HC1. The crude product was then immediately
dissolved in a minimum nnount of methylene chloride (about 150 mis.)
and placed in a separatory funnel. The bottom layer (methylene chlo-
ride and product) was then filtered through a 5.5 cm. Buchner funnel
half-filled with anhydrous MgSO The resulting clear, yellow solution
was placed in a large crystallizing dish along with 250 mis. of
absolute ethanol. The resulting solution was then partially evaporated
at room temperature under a stream of nitrogen which had been passed
through a drying tube filled with anhydrous CaSO4. This resulted in
the formation of a large amount of long thin needles. Filtration
under vacuum produced 18.90 g. of the desired product, m.p.: 62-62.50C.
Further evaporation under nitrogen followed by chilling to -15 C. pro-
duced 2.96 g. of product, m.p.: 60-60.50C. The percent yield obtained
(cumulative) was 89 percent. The melting point of the first crop
agreed perfectly with that reported by Thompson.
2. Meta-(2-vinyloxy)ethoxy-B-nitrostyrene.-- The correspond-
ing meta-(2-vinyloxy)ethoxybenzaldehyde was prepared in a manner entirely
analogous to that for the previous monomer on a 0.3 mole scale. 41.88
g. (73 percent yield) of colorless liquid were obtained by vacuum dis-
tillation, b.p.: 940C. at 0.17 mm Hg. This benzaldehyde crystallized
to form colorless needle crystals, m.p.: 41-42 C. The physical charac-
teristics agreed with thosereported by Thompson and the spectroscopic
data supported the structure.
Attempts to synthesize meta-(2-vinyloxy)ethoxy-2-nitrostyrene
by the method of Thompson produced good yields of a yellow crystalline
material, m.p.: 113-113.5C. Nash's reported melting point was 112-
1130C. for this compound. Thompson demonstrated that this compound
was actually meta-(2-hydroxy)ethoxy-3-nitrostyrene, the product of
acid catalyzed hydrolysis 3f the corresponding vinyl ether.
A repeated attempt was made to synthesize this compound by
Thompson's method with certain o-.difications as described in th2 pre-
vious synthesis. AEter the yellow precipitate was filtered and washed
with chilled deionized water, an nmr spectrum of the crude product indi-
cated that the vinyloxy group was still intact. Rcrystallization from
ethanol aid water as described by Thompson gave the alcohol exclusively.
The synthesis w3s repeated on a 0.0328 mole scale and the crude pro-
duct was dissolved in a minimum amount of CCI4 (50 mls.), placed in a
separatory funnel, and the lower layer filtered through anhydrous
MgSO4. The superficially dried solution was then chilled to -150C.
for 48 hrs. during which time many small "nodules" of bright yellow
product formed. These were scraped loose with a spatula, filtered,
and dried under vacuum for 12 hrs. at room temperature yielding 6.95 g.
(93 percent yield) of the desired product, m.p.: 53-53.50C.
The nmr spectrum (CDC13) of the compound, which is shown in
Figure 2, included a 2-proton AB quartet for the nitrovinyl protons,
THA = 1.98, TH = 2.45 (JAB = 14.2 hz.); a 4-proton multiplet for the
aromatic protons, T = 2.48-3.10; a 1-proton quartet for the a-proton
on the vinyloxy group, T = 3.46 (JGB cis = 6.9 hz., Jc tras = 14.2
cis a3 traas
hz.); and a 6-proton multiplet for the ethoxy group and the 2-protons
of the vinyloxy group, T = 5.56-6.05. The infra-red spectrum of the
ccempound included absorptions at 1620 and 1640 cm, strong and sharp,
3 C=C in vinyloxy group; 1610 and 1601 cm, median and sharp, v C=C
In aromatic group; 1640 cm, overlapping with 1640 cm absorption
from vinyloxy group, N C=C in nitrovinyl group. This assignment was
made by comparison of the spectrmn with that of neta-methoxy-S-nitro-
styrena. The ultra-violet spectrum in ethanol was characterized by an
absorption at X 304 mU ( 1 = 12,500); and X = 246 m 1 ( =
3. r- r -(2-vin ,'.' l-r:..~- --f :.ros tyrene.-- The benzalde-
hyde was prepared on a 0.5 mole scale by the method of Thompson. Vacuum
-------------~--- ---;--;-- --------i
v~ c;u=z~;szr-----.~ ~~-~Ir~------~--- '~~ ~ ~-~,
^'^ -y ^\ -..--_ ^--^- /
"~~ ~ ~~- __._^...__
_____-- -- -- =*,f~= ~ --- -----.;r
~ ~" -Z -l '""' T ^ ^" :3>
o o o
0~~~-- / --. fi.(
distillation of the crude product (b.p.: 1100C. at 0.2 mm Hg) yielded
88.6 g. (92.5 percent yield) of colorless oil. The physical properties
agreed well with those reported by Thompson and the spectral proper-
ties supported the proposed structure.
The B-nitrostyrene was synthesized on a 0.037 mole scale using
the previously described method. The crude product was dissolved in a
minimum amount of CH2C12 (100 mls.) at room temperature, filtered, and
added to 150 mls. of 95 percent ethanol. The resulting solution was
partially evaporated under a stream of air and chilled to -150C. After
24 hrs., the yellow needle crystals were filtered and dried under va-
cu'n. 12.30 g. (60 percent yield) of purified product were obtained,
m.p.: 108-108.50C. This value agreed well with that reported by
B. Cionic olationc ltio.n Studies of the (2-vinyloxy)ethxy- substitu-
1. Cationic polynLeriza tion of para-(2-vinv!oxy)ethioxy--nitro-
styr na.-- 1:1 polymerization of this monomer was conducted on a 1.356
g. scale. The monomer was dissolved in 125 mls. of methylene chloride
and polymerized with 5 mis. of BF gas (4 mole percent). 0.865 g. (64
percent conversion) of deep yellow amorphous polymer was obtained by
precipitation in methanol. The infra-red spectrum included a fairly
strong absorption at 1630 cm1 which was assigned to the nitrovinyl
moeity after comparison with the infra-red spectrum of para-,netho:xy-B-
nitrostyrene. The intrinsic viscosity in methylene chloride was 0.21
dl/g. The molecular weight was determined to be M = 5.2 x 10 using
a Mechrolab vapor pressure csrmometer. The melt temperature of the poly-
mer was 120-125 C.
The above polymer was cross-linked by reacting a solution of
0.5 g. of the polymer in 20 mis. of dry methylene chloride with 0.5 ml.
of sodium ethoxide in ethanol (1 mmole/ml.). Conversion to insoluble
material was complete. The infra-red spectrum of the grayish material
included an absorption at 1608 cm-I for the aromatic nucleus; but no
absorption at 1630 cm- was apparent, indicating that reaction of the
nitrovinyl groups was essentially complete. The insoluble polymer
gave a melt temperature of 2350C. with decomposition.
2. Cationic polymerization of meta-(2-vinyloxy)-ethoxy-i-
nitrostyrene.-- The cationic polymerization of the meta isomer was
effected using a similar procedure. One gram of monomer was polymerized
in 30 mls. of dry methylene chloride using 1 mole percent BF3. 0.083
g. of methnol.insoluble polymer (8.3 percent conversion) was obtained.
The infra-red spectrum of the polymer contained an absorption at 1602
cm, which was assigned to the aromatic nucleus, and an absorption at
1640 cm1 for the pendant nitrovinyl moeity. The intrinsic viscosity
of the polyuer was 0.14 dl/g. in methylene chloride and the melt temper-
ature of the amorphous yellow polymer was 85-950C.
This polymer was cross-linked by dissolving 0.5 g. of the
above polymer in 20 mis. of dry methylene chloride and reacting the
polymer with 0.05 ml. of sodium ethoxide in ethanol (1 nimole/ml.). Con-
version to insoluble material was quantitative. The infra-red spectrum
included a broad absorption at 1600 cm which was assigned to the
aromatic nucleus and a shoulder at 1640 cm- which indicated that the
reaction of the nitrovinyl group was not complete. The amber-colored
polymer gave-no melt temperature up to 2600C. although it discolored
at about 2500C.
3. Cationic polymerization of ortbo-(2-vinlyoxy)ethoxy-_-
nitrostyrene.-- 2.35 g. of monomer were placed in a 250 ml. erlenmeyer
flask which had previously been flamed and cooled. A serium cap was
placed on the flask and wired in position. A hypodermic needle was
placed in the cap to serve as a vent during evacuation of the vessel
in the vacuum chamber of the Dri-Lab. After evacuation, the atmosphere
in the vessel was replaced with dry N2 in the Dri-Lab and the needle
removed. The flask was removed from the Dri-Lab and 50 mis. of CH2C12,
which had been redistilled and dried over 3A molecular sieves, were
added. The flask was then placed in a. Lsopropanol-dry ice bath and
chilled to -75 C. 7 inls. of BF3 gas (3 mole percent) were then intro-
duced with a hypodermic syringe. There was an instant flash of red on
the surface of the solution which disappeared upon vigorous swirling.
After 30 minutes the light amber solution was added dropwise, through
a filter, into 75 mls. of vigorously stirred mathaiol. The flocculent
yellow poly-aer was filtered and dried under vacuum. Conversion to
polymer was essentially quantitative. The melt temperature of the
polymer was 90-1000C. and its intrinsic viscosity was 0.25 dl/g. The
infra-red spectLun of the polymer was characterized by the lack of the
strong 1620 cm- peak from the C=C stretch of the vinyl ether and the
presence of a weak peak at 1625 cm for the C=C stretch of the 6-nitro-
An attempt to cross-link this polymer by the previously de--
scribed method gav3 no significant amount of precipitate.
C. Anionic Polynerization Studies of (2-vinlyoxy)ethoy-substituted
1. Anionic polymerization of meta-(2-vinyloxy)ethoxy,-
nitrostyrene.-- 1.95 g. of monomer were placed in a 60 ml. erlenmeyer
flask and dissolved in 40 mls. of 50 percent THF in absolute ethanol.
0.08 ml. of sodium ethoxide in ethanol solution (1 mmole/ml.) was added
and the solution stirred at 250C. for 24 hrs. The precipitated polymer
was centrifuged and washed twice with methanol. The polymer was then
dried under vacuum for 24 hrs. 1.26 g. (64 percent conversion) of
white powdery polymer were obtained. The product was found to be insol-
uble in all common organic solvents tried but soluble in N,N-dimethyl-
aniline and hexamethylphosphotriamide (HIMPA). The intrinsic viscosity
of the polymer in HMPA at 280C. was 0.08 dl/g. The infra-red spectrum
of the polymer indicated that the vinyl ether group was still intact
absorptions at 1620 cm and 1640 cm1). It was also interesting to
note that on extended contact with air at room temperature the polymer
became completely insoluble in all solvents tried including MIPA, appa-
rently due to cross-linking through the pendant vinyloxy groups. The
infra-red spectrum of the polymer showed that at least some of the
vinyloxy groups were yet intact as indicated by the continued presence
of the 1620 cm and 1640 cm absorptions.
2. Anionic polymerization of Dara-(2-vinylox )ethoxy-B$-
:'to *; r.: .-- 2.35 g. (10 mrnoles) of monomer were dissolved in 50
ml. of 60 percent THF in absolute ethanol. The polymerization was
carried out as described for the meta isomer. 1.54 g. (65.5 percent
conversion) of white powdery polymer were obtained. The intrinsic
viscosity of the polymer was 0.07 dl/g. in HMPA at 23 C. It decomposed
at 235 C.
The vinyloxy groups were once again left intact as indicated
by infra-red absorptions at 1620 cm and 1640 cm. A sample of this
polymer, which had been stored in non-dried air for an extended period,
was found to be insoluble in H4PA indicating some cross-linking. Both
absorptions were still present in the infra-red indicating the presence
of some yet unreacted vinyloxy groups.
3. Attempted anionic polymerization of ortho-(2-vinyloxy)-
ethoxy- -nitrostyrene.-- This monomer did not polymerize in the pres-
ence of sodium ethoxide. Monomer was recovered almost quantitatively
after an attempted polymerization using the above described method.
D. Analysis of the Conformation of Para-(2-vinylo )toxythoxy--nitro-
1. Ultra-violet analysis.-- The ultra-violet spectrum of the
para isomer in methylene chloride (5 x 10-5 M.) was obtained as was the
spectrum of the cationically initiated polymer (1 x 104 M. expressed
as concentration of monomer units). The spectrum could not be taken
below 230 my due to solvent absorption. Both spectra appear in Figure
5, page 65. The spectrum of the monomer included absorption maxima at
x. = 263 my (e = 9,700) and max. = 300 my (c =12,300). The spectra
of the polymer included absorption maxima at max. = 263 my (e' = 5,120)
and X = 300 mp (E' = 5,900) where E' is defined in terms of con-
centration of monomer units.
2. Synthesis of para-nitro-(2-vinyloxy)etho beanzne.--
10.12 g. (0.073 mole) of para-nitrophenol were dissolved in 100 mls.
of absolute ethanol in a 500 ml. round-bottom flask. To this solution
was added a solution of 9.10 g. of 85 percent potassium hydroxide dis-
solved in 100 mls. of absolute ethanol. Yellow crystals formed imnaedi-
ately. The solvent was removed by distillation under vacuum with
warming. Any remaining water was removed as the benzene-water azeo-
The salt was then reacted with a-chloroethyl vinyl ether in
dimethylfonnamide in the previously described manner. After 12 hrs.
of reaction time, the resulting mixture was chilled in an ice-water
bath and added to 200 mis. of ether in a separatory funnel. This mix-
ture was extracted twice with 150 ml. aliquots of chilled 2 percent
aqueous potassium hydroxide and once with 200 mls. of chilled deionized
water. The ethereal layer was then filtered through anhydrous magne-
sium sulphate aid the solvent was then removed by distillation under
vacuum at room temperature. The tan solid was then dissolved in a
minimum amount of methylene chloride in a crystallizing dish aid to
this was added 100 mis. of absolute ethanol. The methylene chloride
was then evaporated off under a streak of dry nitrogen with no waning.
This procedure yielded 8.72 g. (64.6 percent yield) of light tan crys-
cais, m.p.: 73-74 C. Recrystallization of the product by the same
method gave 6.47 g. (75 percent recovery) of white crystals, m.p.:
73-74 C. The infra-red and nmr spectra supported the proposed struc-
3. Infra-red analysis.-- The infra-red spectrum of para-
(2-vinyloxy)etho-y-6-nitrostyrene in methylene chloride, as well as in
a potassium bromide pellet, was obtained. Both spectra contained absorp-
tions at 1199 cm-1 (V C-0 of vinyloxy group), 1620 cm- (v C=C vinyloxy
group), 163) cm- (v C=C nitrovinyl group), and a barely perceptible
shoulder at 1640 cm. The shoulder was assigned to the vinyloxy group
as well. This assignment was confirmed by obtaining the infra-red spec-
trum of para-nitro-(2-vinyloxy)ethoxybenzene. The lack of the
nitrovinyl absorption facilitated the observation of both the 1620
and 1640 cm absorptions typical of vinyl ethers. Major absorptions
of these spectra as well as that of $-chloroethyl vinyl ether appear
in Figure 4, page 61. This and other data appear in Table 5, page 62.
4. Nuclear magnetic resonance analysis.-- The nmr spectra
of ortho-, meta-, and para-(2-vinyloxy)ethoxy-3-nitrostyrenes, para-
nitro-(2-vinyloxy)ethoxybenzne, (2-vinyloxy)ethoxybenzene, and 5-chlo-
roethyl vinyl ether were obtained in deuterated chloroform. The spec-
tra of the vinyloxy groups (50 hz. sweepwidth, 250 sec. speed) were
analyzed in detail. Each spectrum was run twice of more to insure
reproducibility. Part of the spectrum of the terminal methylene group
was found to overlap with the spectrum of the ethyloxy group making
complete analysis impossible. However, the low field half of the AB
quartet assigned to IH (trans to the a-proton) was not subject to
interference; hence, the geminal coupling constant could be obtained
for each vinyloxy group. These constants and other data appear in
Table 6a, page 63.
Studies of the Anionic Polymerization of Some
A. Synthesis of Substituted j-nitrostyrenes
Fifteen substituted 3-nitrostyrenes and -nitrostyrene were
synthesized for this study. Since the procedure for synthesis of these
compounds was the same as that previously described for ortho(2-vinyl-
oxy)ethoxy--nitrostyrene, it will not be described in full here. How-
ever, due to widely differing polarities of the various compounds, the
crude products were recrystallized using different solvent systems.
The method of work-up will be described for each compound for this
1. L-nitrostyrene.-- This compound was prepared on a 0.25
mole scale. The crude product was recrystallized twice from warm 95
percent ethanol to give 13.7 g. (37 percent overall yield) of yellow
needle crystals, m.p.: 56-57 C. (lit.2 56-570C.).
2. Meta-methoxy- -nitrostyrene. -- This isomer was prepared
on a 0.10 mole scale. The crude product was recrystallized once from
warm ethanol. The yield was 10.29 g. (57.5 percent yield) of pale
yellow plates, m.p.: 90-92 C. (lit.2 920C.).
3. Pari-methoxy-a-nitrostyrene.-- This monomer was synthe-
sized on a 0.10 mole scale. The crude product was recrystallized from
hot 95 percent ethanol. The yield was 13.02 g. (72.6 percent yield)
of bright yellow plates, m.p.: 85-86.50C. (lit53 830C.).
4. Ortho-methoxy-3-nitrostyrene.-- This styrene was also
prepared on a 0.10 mole scale. The crude product was recrystallized
from warm 95 percent ethanol and water giving 10.72 g. (60.2 percent
0 20 0
yield) of yellow needles, m.p.: 47-480C. (lit. 47-48 C.).
5. Meta-methyl-B-nitrostyrene.-- This compound was synthe-
sized on a 0.208 mole scale. The crude product solidified as usual in
the last step of the synthesis when the reaction mixture was added
dropwise to water, ice, and hydrochloric acid. Water is eliminated
from the condensation product in this step. After the solid yellow
material was filtered a.nd washed with deionized water as usual, the prod-
uct was found to liquify at room temperature. As a result the compound
was purified by vacuum distillation to yield 18.67 g. (55 percent yield)
of yellow oil, b.p.: 800C. at 0.15 mn Hg, (lit54 1330 at 2.8 mm Hg),
nD25 = 1.625.
6. F3 j -.'-,hyl-^-niLrosti'r-:-.-- This compound was synthe-
sized on a 0.25 mole scale. The crude product was dissolved in a mini-
mum amount of hot 95 percent ethanol, filtered, and chilled to 0.150C.
for 24 hrs. The yield was 25.1 g. (62.5 percent) of lovely yellow
needles, m.p.: 101.5-102 C. (lit. 102 C.). Subsequent recrystalliza-
tion failed to change the melting point.
7. Ortho-fluo:o- -nitrostyrene.-- This compound was synthe-
sized by the method of Thompson on a 0.20 mole scale. The crude pro-
duct was recrystallized from ethanol and water yielding 15.40 g. (46
0 54 o
percent yield) of product, m.p.: 53-54 C. (lit. 54 C.).
8. Meta-fluoro-S-nitrostyrene.-- This monomer was synthe-
sized on a 0.085 mole scale. The crude product was recrystallized from
warn 95 percent ethanol by chilling to -150C. The crystalline product
was filtered and dried under vacuum yielding 7.19 g. (50.6 percent
0 54 o
yield) of product, m.p.: 45.5-460C. (lit5 45-47C.).
9. Para-fluoro-8-nitrostyrene.-- This synthesis was carried
out on a 0.20 mole scale. The crude product was recrystallized from
a minimum amount of warm 95 percent ethanol. The product was filtered
and dried under vacuum at room temperature for 24 hrs. The yield was
15.2 g. (45 percent) of yellow needles, m.p.: 100-101 C. (lit4 100-
10. Ortho-chloro-3-nitrostyrene.-- This synthesis was carried
out on a 0.25 mole scale. The crude product was recrystallized from
a minimum amount of 95 percent ethanol. The yield was 26.5 g. (57.6
percent yield) of long yellow needles, m.p.: 46.5-47.5 C. (lit. 47-
11. Para-chloro-B-nitrostyrene.-- This synthesis was carried
out on a 0.10 mole scale by the previously described method. The crude
product was dissolved in 200 mis. of warm ethanol, filtered, and to
this was added 75 mls. of deionized water. The solution was then
chilled to -150C. for 24 hrs. The yield was 11.5 g. (62.5 percent
yield) of yellow needles, m.p.: 113-1140C. (lit.5 113-114C.).
12. Ortho-bromo-2-nitrostyrene.-- This synthesis was carried
out on a 0.14 mole scale by the previously described modified Thiele
reaction. The crude product was dissolved in 125 mis. of warm 95
percent ethanol, filtered, and chilled to -150C. for 24 hrs. yielding
15.80 g. (49.5 percent yield) of yellow needles, m.p.: 86-86.5 C. (lit.2
13. Meta-bro.no-S-nitrostyrene.-- This synthesis was carried
out on a 0.14 mole scale by the same method. The crude product was
again dissolved in a minimum amount of hot 95 percent ethanol (175 mis.)
and chilled to -150C. for 24 hrs. The long yellow needles were filtered
and dried under vacumn at room temperature for 24 hrs. The yield was
14.49 g. (45.4 percent yield) of product, m.p.: 60-610C. (lit. 59-
14. Para-bromo-3-nitrostyrene.-- This monomer was synthe-
sized on a 0.134 mole scale. The crude product was dissolved in 75
mis. of TIH and to this was added 100 mis. of 95 percent ethanol. The
resulting solution was chilled to -150C. for 24 hrs. The resulting
crystals were filtered and dried under vacuum at room temperature for
24 hrs. The yield was 9.93 g. (32.5 percent yield) of purified pro-
duct, m.p.: 148.5-149C. (lit.7 1750C.). Subsequent recrystallizations
failed to change the melting point. Due to this discrepancy in melting
points, the coimpou-nd was analyzed in greater detail.
The nmr spectrum of the compound was comprised of a 2-proton
AB quartet for the nitrovinyl group, THA = 2.01, THI = 2.45 (J3 =
14 hz.); and a 4-proton A2 2 quartet for the aromatic protons, THA
2.37, THB = 2.58 (JAB = 9 hz.). The infra-red spectrum included strong
sharp absorptions at 1628 cm- (v C=C of nitrovinyl group) and 1580
cm (V C=C of aromatic nucleus).
Analysis: Calculated for C8H6NO2Br, Mwt. 223.05, percent:
C, 42.13; H, 2.65; N, 6.14; Br, 35.04. Found, percent: C, 42.40;
H, 2.59; N, 6.20; Br, 35.26.
15. Meta-nitro-3-nitrostyrene.-- This monomer was synthesized
on a 0.25 mole scale by the previously described method. The crude
product was dissolved in a minimum amount of warm 95 percent ethanol,
filtered, and chilled to -150C. for 24 hrs. yielding 13.7 g. (28.3
percent yield) of product, m.p.: 121.5-122.50C. (lit58 122-1240C.).
16. Para-nitro-B-nitrostyrne.-- This synthesis was carried
out on a 0.10 mole scale by the previously described method. The crude
product was dissolved in a minimum amount of acetone, diluted with 95
percent ethanol, and recrystallized out with water. This method
yielded 3.7 g. (19 percent yield) of product, m.p.: 204-2050C. (lit9
B. Determination of the Rate of Pcopagation in the Anionic Polymeri-
zation of Certain Meta-and Para-substituted a-nitrostyrenes and
Essentially, the same procedure was used in the study of each
monomer so, to avoid repetition, the procedure will be described only
once in its entirety. Variations, when deemed necessary, will be de-
1. &-nitrostyrene.-- 10.00 mmole quantities (1.490 g.) of
the monomer were weighed out to the nearest mg. in 60 ml. weighing
bottles which had been scrupulously washed, rinsed with acetone, and
oven dried at 1100C. Each sample was dissolved and diluted to 40.0
mis. (0.250 M.) in a solvent mixture prepared by mixing 2 parts by
volume of absolute ethanol with 1 part of purified6 THF. The solu-
tions were then equipped with magnetic stirrers and Taflon-covered mag-
nets and placed in a thermostatted (28 + 0.10C.) bath and allowed to
come to thermal equilibrium. Stirring speed was maintained at a moder-
ate rate to minimize conversion of mechanical enrgy to thermal energy.
Using a 0.25 ml. tuberculin syringe, 0.20 ml. of sodium ethoxide/etha-
nol (0.105 mmole/ml.) was injected at time t = 0, giving an initiator
concentration of 5.25 x 104 M. At time (t), 0.5 ml. of 1 M. sulfuric
acid in ethanol was injected to terminate polymerization. The resulting
precipitated polymer was then centrifuged in carefully washed pre-
weighed centrifuge tubes, washed once with methanol, recentrifuged,
and dried under vacuum (0.025 mm Hg) for 12 hrs. at room temperature.
The product was then weighed to the nearest tenth milligram.
Polymer yields were plotted in terms of moles of monomer units/
liter of solution converted to polymer. The slope of that line gives
the cbserved rate of polymerization vp, expressed as moles/liter/sec.
The rate constant, k was then calculated using the expression v =
k [M][M], whore [M ] is assumed to be equal to initiator concentration
2. Meta,B -dinitrostyrene.-- Due to the limited solubility
of this compound in the chosen solvent system, only 5.00 mmole samples
(0.370 g.) of the mono.::cr were polymerized. In all other respects,
this experiment was carried out in a manner identical to that for
3. Para ,-dinitrostyrene.-- Due to the relatively low polar-
ity of this compound in this solvent system, its solubility was quite
limited. As a result, 5 mmole samples of the monomer (0.970 g.) were
dissolved in 140 mis. of solvent. Initial initiator concentrations
were 5.25 x 10 M. as before.
Other monomers were polymerized either on a 5.00 mmole or
10.03 mmole scale depending upon the availability of the monomer as
well as its molecular weight. The data from these experiments is
tabulated in Table 1 and plotted in Figures 9-18, pa-.es 78 through 87.
The calculated propagation rate constaits (k ) appear in Table 10,
C. Determination of the Rate of Initiation of Two Reepresentative
Monomers, Para-methoxy-g-nitrostyrene and g-nitrostyrene
The rate of reaction of sodium ethoxide with monomer was de-
termined in the following manner. A solution of para-methoxy-2-nitro-
styrene in the usual solvent system (33 volume percent T1F in absolute
ethanol) was prepared with a concentration of 3 x 10-5 M. and 3.9 mis.
of the solution were placed in a thermostatted (25 0.10C.) qJartz cell
in the ultra-violet spectrophotometer under a N2 purge. The reaction
was monitored by measuring the absorbance at the mo.iner's absorption
maximum at = 348 mp (E = 20,600). At time t = 0, 0.1 ml. of
sodium ethoxide in absolute ethanol (5 x 10-2 M.) was injected rapidly
with a tuberculin syringe (0.25 ml.). The resulting solution, con-
training about a 10-fold excess of initiator (5 x 10- M.) :as quickly
stirred and bthe progress of reaction followed by watching the steady
decrease in absorbance. Readings were taken every 10 seconds. The
Kinetic Data of Propagation Reactions
[NaOEt] = 5.25
x 10-4 M.
__ I_ __ __ __
ii I ---C------------~------------- _
TABLE 1 continued
Monomer Run Monomer
(sec.) Yield Cony.
(D.) meta-methoxy-4- 1 0.895 0.125 30 13.4 1.50
(trial 2) 2 0.895 0.125 45 24.8 2.88
3 -0.895 0.125 60 38.2 4.27
4 0.895 0.125 75 47.5 5.30
(E.) para-methoxy-4- 1 1.790 0.250 30 7.0 0.391
(trial 1) 2 1.790 0.250 45 13.5 0.755
3 1.790 0.250 60 19.1 1.06
4 1.792 0.250 75 34.2 1.90
(Trial 2) 1 1.790 0.250 30 9.0 0.502
2 1.790 0.250 75 17.5 0.978
3 1.790 0.250 60 22.1 1.23
4 1.790 0.250 90 31.0 1.73
-----~ ----------------------------- ------- -------
TABLE 1 continued
(H.) meta-bromo-- 1 1.140 0.125 31 32.6 2.86
2 1.141 0.125 45 48.6 4.25
3 1.140 0.125 60 64.2 5.62
4 1.140 0.125 90 73.9 6.48
(I.) para-bromo-S- 1 1.140 0.125 30 25.2 2.24
2 1.140 0.125 46 37.6 3.40
3 1.140 3.125 60 47.4 4.15
4 1.141 0.125 75 56.5 4.95
(J.) meta,O- 1 0.970 0.125 10 13.1 1.35
(Trial 1) 2 0.970 0.125 15 17.5 1.81
3 0.970 0.125 20 20.0 2.03
4 0.970 0.125 30 24.5 2.53
(Trail 2) 1 0.970 0.125 15 15.9 1.64
2 0.970 0.125 30 21.9 2.26
3 0.970 0.125 45 29.0 2.99
rate constant was determined by plotting log (Dt OD )/[I] vs. t
where I is the initiator concentration. The slope of the resulting
plot is -k., the rate constant of initiation. The plot appears in
Figure 6, page 74. The rate constant thus determined was k. = 2.86 1.
mole- sec. The rate constant of initiation for j-nitrostyrene was
carried out in the same manner. The rate of reaction was obtained by
monitoring the absorption maximum at 309 mp (E = 12,000). This reaction
was also run under N2. Due to the lower E for this monomer, a monomer
concentration of 5 x 10 M. was used. The initiator concentration
was again 5 x 10 M. The plot of data appears in Figure 7, page 75.
The rate constant obtained was k. = 3.51 1. mole sec.
D. Effect of Chances in Initiator Conceatration on the Rate of Anionic
Polymerization of $-nitrostyrene
10 mmole quantities of S-nitrostyrene, which had been freshly
prepared and recrystallized, were weighed out into the 60 ml. flasks
and diluted to 43 ml. with the usual 33 percent THF in ethanol.
The solutions were allowed to come to equilibrium with stirring
in the 280C. bath. To each was added a varied amount of the initiator
solution via a 0.25 ml. syringe. Each was allowed to polymerize for
30 sec. before termination. After termination with 0.5 mmole of
hydrochloric acid, the polymer was centrifuged, washed with methanol,
and dried under vacuum and weighed to the nearest 0.1 mg. A plot of
this data appears in Figure 19, page 90.
Kinetic Data for Changing Initiator Concentration
Vol. of Cone. of Polymer Percent
Initiator Initia or Yield Cony.
(ml.) M x 10 (mg.)
0.05 1.01 3.9 0.26
0.10 2.02 8.5 0.57
0.15 3.03 12.3 0.82
0.20 4.05 16.7 1.12
0.25 5.06 21.6 1.45
0.30 6.07 29.3 1.97
E. Detennination of the Molecular JWeight Distribution Curves of Some
Representative Moiosubstituted Poly-8-nitrostyrenes
The molecular weight distribution curves of some of the DMF
soluble polymers obtained during the rate of propagation study were
determined by gel permeation chromatographic (GPC) analysis. 1 wt.
percent solutions of the polymer (3 mis.) were prepared by dissolving
the finely ground polymer in DMF either at room temperature of at 1100C.
depending upon the apparent solubility. The resulting solutions were
filtered through median porosity sintered glass filtering crucibles
and chen chromiatographed on the GPC. Two typical molecular weight
distribution curves appear in Fig&res 7 and 3, pages 75 and 76. Using
the laborious method described in the instrument literature, the number
average molecular length, An, and weight average molecular length, A ,
(both in angstroms) were calculated. Using a calibration curve derived
from polystyrene standard samples, values for the number and weight
average molecular weights (M and Fi respectively) were determined.
The results of these determinations are tabulated in Table 5, page 62.
It should be noted that poly-para-methoxy-P-nitrostyrene and poly-B-
nitrostyrene were found to not dissolve completely, even when heated
to 1100C. Butler reported depolymerization of poly--nitrostyrene
under such conditions. Although depolymerization was not proven in
the present work, it was probably occurring in the case of these two
F. The Role and Mechanism of Initiation and Termination in the Anionic
Polyrmerization of Meta and Para,p-dinitrostyrene
1. Polymerization of para,6-dinitrostyrene.-- 1.94 g. of
monomer were dissolved in 150 mis. of 33 percent THF in absolute ethanol
and reacted with 5 mole percent sodium ethoxide. The addition of ini-
tiator resulted in the formation of a deep red solution which slowly
changed to a very dark amber color. The polymerization was carried
out over a 24-hr. period. rhe dark anber mixture was then acidified
and centrifuged. The yellow precipitated product was washed with
methanol, recentrifuged, and dried under vacuum at room temperature
yielding 0.10 g. (5.2 percent conversion) of light amber amorphous
solid, T : 295-300 C. (dec.). Insufficient yield was obtained for an
intrinsic viscosity determination.
The infra-red spectrum of the product included a strong absorp-
tion at 1350 cm, conjugated nitro; strong 1525 cm, nitro; weak 1600
cm, v C=-C aromatic; medium 1100 cm, V C-0 of aliphatic ether. The
strong 1635 cm- (v C-0 of nitrovinyl) was not detectable and there was
no indication of any significant absorption between 1200 and 1250 cm.
(V C-0 of aromatic ether).
2. Polymerization of meta,B-dinitrostyrene.-- This reaction
was carried out as described for the para isomer except only 50 mis. of
solvent were used. 0.430 g. (22 percent conversion) of a light amber
glass-like solid was obtained, T : 290-2950C. (dec.), [n] = 0.11 dl/g.
When this polymerization was carried out in pure THF, only
0.181 g. (9.3 percent conversion) was obtained, [n] = 0.06 dl/g. in
The infra-red spectra of the two products were identical and
included strong absorptions at 1375 cm and 1450 cm, nitro groups;
medium at 1560 cm, V C=C aromatic; weak at 1100 cm, V C-0 aliphatic
ether linkage. Again, there was no indication of an aromatic ether.
3. The reaction of sodio-malonic ester with oara _-dinitro-
styrene and determination of the structure of the product.-- The
method of Perckalin and Sopova62 was used to carry out this reaction.
1.30 3. of para-B-dinitrostyrene (0.0067 mole) suspended in 203 mis.
of dry methanol at room temperature was added to the reaction mixture
of 1.43 g. (0.00837 mole) diethyl malonic ester, 0.186 g. of sodium
(0.0081 mole), and 15 mls. of methanol at room temperature. The mono-
mer quickly dissolved forming a gradually darkening amber solution.
The red color, characteristic of the reaction of sodium ethoxide with
this compound, was not present. The solution was then heated to 450C.
and kept at this temperature ( 50C.) for two hours. The dark amber
solution was then chilled in ice water and acidified with glacial ace-
tic acid (50 mls.) followed by addition of 25 mls. of concentrated hydro-
chloric acid: The product was then extracted with ether and the ether
removed by distillation.
The product was not isolated in pure form although the nmr
spectrum of the crude product, which included a 4-proton A2B2 quartet
at THA = 2.70, TH = 3.11 (JAB = 9 hz.); a 2-proton doublet at T = 4.93;
a 2-proton multiplet at T = 5.5-6.2; and a 6-proton doublet at T = 6.25,
indicated a fair degree of purity.
This nmr spectrum indicates that a 1:1 adduct was obtained.
However, it does not distinguish between carbanion attack on the a-
carbon as opposed to attack on the -carbon. Apparently, trans-esteri-
fication occurred between the ethyl ester and solvent as indicated by
the methoxy singlets.
The cru a product was placed in a 100 ml. round-bottom flask
with 35 mis. of concentrated hydrochloric acid. The resulting mixture
was refluxed for 24 hrs. The mixture was then placed in a separatory
funnel while still hot aid the bottom layer was separated into another
separatory funnel. Upon cooling to room temperature, 0.122 g. of
amber crystalline solid (m.p.: 118-119 C.) fornned on the sides of the
The aqueous solution was found to be soluble in ether due to
the high acid content. The acid was then partially neutralized with
aqueous potassium hydroxide and the product was then extracted with
ether. Distillation of the ether under vacuum yielded 1.09 g. of anber
solid contaminated with an amber oil. The solid was placed in a sin-
tered glass filtering crucible and washed with benzene. This effectively
removed the oil and the resulting light amber powder was dried in a
1100C. over for 24 hrs.
The nmr spectrum (acetone-d6) of the compound, when compared
with Sadtler spectrum number 6595 (phenylsuccinic acid), conclusively
identified the structure of this product as para-nitrophenylsuccinic
acid. The spectrum included a 4-proton A2B2 quartet for the aromatic
protons, THA = 1.75, TH = 2.33 (J = 9 hz.); a one-proton ABC quartet
for the benzylic proton, THA = 5.70 (JAB = 9 hz., JAC = 6 hz.); and 2
one-proton ABC quartets for the non-equivalent methylene protons THB =
6.83, THC = 7.33 (Jge = 17 hz.).
The infra-red spectrum (KBr pellet) of the product included
a broad absorption between 3500 a.d 2500 cm; (V 0-H of a hydrogen
bonded carboxyl group) strong absorption at 1710 cmn- (V C=O); and a
medium absorption at 1600 cm-1 (V C=C aromatic).
The melting point of the compound (218-218.5 C.) agreed well
with that reported3 for para-nitrophenylsuccinic acid and the spectral
data supported that assignment.
The total yield was 1.21 g. (75 percent yield).
4. Reaction of sodio-malonic ester with meta,3-dinitrostyrene
and determination of the structure of the product.-- This reaction
was carried out in an identical manner as that previously described
for the para isomer. The reaction was carried out using 1.93 g.
(0.0102 mole) of meta,8-dinitrostyrene, 2.04 g. of nalonic ester, and
0.284 g. of sodium metal.
The nmr spectrum of the aliphatic protons of the crude product
was essentially identical to that of the previously described malonic
This crude product was treated with concentrated hydrochloric
acid as before. 0.107 g. of light amber crystals (m.p.: 106-1090C.)
formed \ihen the aqueous layer of the reaction mixture cooled to room
Work-up of the remaining product yielded 1.839 g. of very light
amber powder, m.p.: 217-2190C.
The infra-red spectrum of the product included a strong broad
absorption at 2400-3400 cm1 ( 0O-H hydrogen bonded); a strong sharp
absorption at 1705 cm- (V C=0); a strong absorption at 1540 cm (-
nitre group); and a weak absorption at 1580 cm- (v C=C aromatic).
The nnr spectrum of the aliphatic protons was essentially
identical to that of the corresponding para-substituted compound.
Although the melting point of this compound was higher thai
the literature value64 of the melting point of meta-nitrophenylsuccinic
acid (2040C.), the spectral data indicates that its structure is analo-
gous to that of para-nitrophenylsuccinic acid. The elemnental analysis
was in close agreement with the theoretical values for meta-nitrophenyl-
5. The relative acidity of poly-meta,3-dinitrostyrene.--
This question was first tested qualitatively by dissolving a small
sample (about 20 mg.) of the polymer in about 10 mls. of dinethylsul-
foxide (iT173). A couple of drops of 1 M. sodium ethoxide, luhen added
to the very light amber solution, produced a very dark amber solution.
This observation prompted a spectroscopic study of the reaction.
A solution of polymer in DMSO of concentration 1.6 x 104
moles/i. (in terms of monomer units) was prepared. It was found to be
transparent from 400-850 mp. Addition of sufficient sodium ethoxide
to give a concentration of 103 M. produced an absorption maximum at
about A = 490 mp, A = 0.30.
The -following experiment was carried out to determine the
reactivity toward monomer of this apparent new species of aiion being
formed. A solution of 0.112 g. of poly-meta,i-dinitrostyrene in 10
mis. of DMSO (dried over 4A molecular sieves for 24 hrs.) was reacted
with 0.2 ml. of 0.5 M. sodium ethoxide in DMSO for 12 hrs. under N2.
0.75 g. of para-bromo-8-nitrostyrene, dissolved in 10 mis. of DMSO, was
then added to the dark amber solution.
A blank containing 10 mls. of DMSO and 0.2 ml. of the sodium
ethoxide solution had been prepared and left standing under N2 for 12
hrs. 0.75 g. of para-bromo-i-nitrostyrene in DMSO was also added to
the blank. At the end of 20 minutes' reaction time with the monomer,
each reaction was terminated with 1 M. HC1 in methanol and added to 100
mls. of vigorously stirred methanol. The solution containing the poly-
meta,i-dinitrostyrene yielded no polymer. The blank yielded 0.36 g.
of poly-para-bromo-b-nitrostyrene (48 percent conversion).
6. The relative acidity of poly-para,8-dinitrostyrene.-- A
solution of the polymer (1 x 104 M. in mnomier units) in dry Di:30 was
prepared. The visible spectrum of the solution was free of absorption
maxima. To this solution was added sodium ethoxide (3 x 10-4 M.).
The resulting amber solution gave an absorption at max. = 433 mp,
A = 0.15.
Another polymer solution (2 x 10 M. in monomer units) in
D.AO was prepared containing 1.5 x 105 M. sodium ethoxide. This solu-
tion was allowed to react for 24 hrs. to reach equilibrium. A solution
of para-methoxy-0-nitrostyrene (4 x 10-5 M.) in DMSO was also prepared.
The planned procedure was to mix the two solutions and monitor the reac-
tion by watching the 348 my absorption maximum of para-methoxy-B-nitro-
styrene which was already known to disappear upon reaction. The absor-
bance of the initial polymer/initiator solution at 348 my was A = 0.40.
Another polymer solution (2 x 10 M. in monomer units) in
D1ISO was prepared containing 1.5 x 10 M. sodium ethoxide. This solu-
tion was allowed to react for 24 hrs. to reach equilibrium. A solution
of para-methoxy-&-nitrostyrene (4 x 10-5 M.) in D:iS3 was also prepared.
The planned procedure was to mix the two solutions and monitor the reac-
tion by watching the 345 m absorption maximum of para-methoxy-6-nitro-
styrene which was already known to disappear upon reaction. The absor-
bance of the initial polymer/initiator solution at 348 in-' as A = 0.05
while that of the initial monomer solution was A = 0.77. Equal amounts
of the two solutions were mixed and the initial a)sorbance of the solu-
tion was A = 0.40. This did not change over a period of one hour. The
expected theoretical value for no reaction would have been 0.41.
7. The reaction b.tw.en meta,g-dinitrostyrene and sodium
ethoxi.d.-- A solution of meta,3-dinitrostyrene (6.6 x 10 M..) was
prep ared in .ZiSO. Sufficient 1 M. sodium ethoxide, in absolute ethanol,
was added to the solution to make it 4 x 103 I. in that compound. The
resulting bright green solution possessed an absorption maximum at
X = 657 iq, A = 0.77.
Whnn a solution of meta,3-dinitrostyrene in DMSO (1 x 10-3 M.)
was rcacted with a less than equipolar amount of sodium ethoxide (1 x
10 M.) the 657 mp peak was initially fairly strong but decreased
fairly rapidly over a period of 3 minutes. As it decreased, a new but
weaker absorption ;iximum appeared at about 490 m9 .
8. The reaction cf pa-a,8-dinitrostyrene with sodium ethoxide.--
A solution of para,B-Jiaitrostyrene (5 x 103 M.) in DHSO containing an
excess of sodium ethoxide (1.5 x 10-2 11.) gave an absorption maximum at
max. = 539 mT, A = 0.46. This value did not change appreciably over
max. u period.
a 10--minute period.
When a solution of the same monomer and same concentration was
reacted with sodium ethoxide in a less than equimolar quantity (1 x 104
M.), an absorption maximum was again observed at 539 mp. However, the
absorbance steadily decreased over a one hour period. No other absorp-
tion maximum could be observed in the visible region. If there was a
weak absorption at 433 mp, it was obscured by the overlapping tail of a
strong absorption in the ultra-violet region, X = 293 mni.
Studies of Certain Aspects of the Ortho-effect
1. Effect of initiator species on polymerizati on of certain
monomers.-- Anionic polyimerizations of several o.tho, meta, and para-
substituted B-nitrostyrenes were carried out on 6 minole scales with dif-
ferent initiators (3 mole percent) to determine the effect of the size
of the initiating ion on the extent of polymnrization. Polymerizations
utilizing hydroxide and ethoxide as initiators were carried out in 33
r.ls. of absolute ethanol while those utilizing t-butoxide were carried
out in 50 mls. of absolute t-butanol. Unless otherwise stated, all
polymerizations were carried out over 24-hour periods at room tempera-
ture with magnetic stirring. No attempts were made to exclude air from
the reaction mixtures.
The precipitated polymers were filtered out in pre-weigd Sin-
tered glass filtering crucibles (medium porosity), washed once with
rmethanol and dried under vacuum at room temperature for 24 hrs. The
results are cabulate2 in Table 3, page 50,
2. Dter u-n-iation of the rate of oolymerLzation of certain
ortho-substituted B-nitrcstyrenes.-- The data in Table 3 prompted a
quantitative investigation of the rate of polymerization of different
The Effect of Initiator Ion on Poly.ner Yields
ortho-fluoro NaOH 1.007 0.263 26.1
NaOEt 1.004 0.264 26.3
NaOtBu 1.006 0.216 21.5
NaOEt* 1.004 0.092 9.16
meta-fluoro NaOH 1.002 0.803 80.1
FaCEt 1.031 0.752 75.2
NaOtBu. 1.000 0.837 83.7
Na)Et* 1.010 0.424 42.0
para-fluoro NaO0 1.002 0.913 90.1
NaOEt 1.001 0.905 90.5
NaOtBu 1.013 0.903 89.7
NaOEt* 1.002 0.643 64.2
ortho-mcthoxy NaOH 1.072 0.000 0.0
1.074 0.000 0.0
1.074 0.008 0.75
1.079 1.016 94.0
N~37t 1.074 1.003 95.8
NaOtBu 1.074 0.272 81.0
*Polymierization time I hr., all others 24 hrs.
TABLE 3 continued
g-nitrostyrene Initiator Feed Yield Percent
(g.) (g.) Conv.
para-methoxy NaOH 1.074 1.029 95.6
NaOEt 1.074 1.018 94.8
NaOtBu 1.074 0.893 83.5
ortho-(2-vinyloxy)ethoxy NaOH 1.413 0.009 0.70
FaOEt 1.418 0.010 0.71
NaOtBu 1.411 0.025 1.77
ortho-substituted B-nitrostyrenes. In addition to the ortho-fluoro com-
pound, ortho-chloro and ortho-brono- -nitrostyrene were also synthesized.
These experiments were carried out using the same general procedure as
was used in the kinetic study of the meta and para-substituted compounds.
A stock solution of initiator was prepared by dissolving 2.3 g.
of metallic sodium in 103 mls. of absolute ethanol in a 250 ml. erlen-
meyer flask covered with a septum. The septumT was vented with a syringe
needle and purged with dried nitrogen during and after the reaction.
The initiator solution was then standardized against potassium acid
phthalate (concentration thus obtained = 1.05 M.).
Because of the expected slowness of these polymerizations, two
mole percent initiator was used. 10 inmole quantities of monomer were
dissolved in 33 percent T[tF (by volume) in absolute ethanol and diluted
to 40.0 mls. (0.250 M.). At tine t = 0, 0.20 ml. of the stock initiator
solution was injected into each mono:er solution and the polymerization
then terminated at time t by acidification. The results appear in
Table 4. A plot of polymer yield [P] expressed in terms of moles of
monomer units per liter versus time appears in Figure 25, page 104.
Kinetic Data of the Anionic Polymerization of
Feed Polymerizaiion Polymer Percent
(g.) Time (sec.) Yield (mg.) Conv.
1.670 83 34.6 2.07
1.670 100 41.5 2.48
1.671 65 26.5 1.58
1.671 120 49.4 2.96
3. The reaction of ortho-substituted -nitrostyrenes with
excess sodium ethoxide.-- These qualitative experiments were carried
out in an effort to determine whether the ortho-effect, as manifested
in the previous experiments, is the primary result of an inhibition of
initiation or propagation or both.
A solution of 3 mmoles of each of the following compounds was
prepared in 8 mis. of 33 percent THF in ethanol; ortho-fluoro, ortho-
chloro, ortho-bro.o, ortho-methoxy, and ortho-(2-vinyloxy)ethoxy- -
nitrostyrene. The nmr spectrum of each solution was recorded with
special attention devoted to the nitrovinyl proton-aromatic proton
region. 5 mis. of the 1.05 M. sodium ethoxide solution were then injected
rapidly into the monomer solutions. The nmr spectrum of the resulting
solution was then taken as rapidly as possible (approximately 30 sec.
after injection). ThseS spectra appear in FiJ.iLcs 26 through 30. It
can be readily seen in each spectrum that the AB quartet (nitrovinyl
protons) is not detectable after 30 seconds.
A Beckman DX-2A double-bean recording spectrophotometer was
used to obtain all ultra-violet and visible spectra.
Beckman IR-8 and IR-10 infra-red spectrophotometers were used
to obtain all infra-red spectra.
A Varian A-60 nmr spectrometer was used to obtain all nmr spec-
tra and unless otherwise indicated, all spectra were obtained using
deuterated chloroform (CDC13) as the solvent.
A Waters GPC 300 gel permeation chromatograph was used with
calibrated polystyrene gel colunns to obtain all molecular weight
A Thomas Hoover Capillary Melting Point Apparatus was used to
obtain the melting points of all monomeric compounds and the melting
points reported are uncorrected.
A Fisher Johns melting point apparatus was us:d to obtain the
melting points of all polymeric materials.
A Vacuun/Atmospheres Corporation Dri-Lab wa: used for all
inert at-io)ph-re work.
Source and Methods of Purification of Reagents
Ortho, meta, and para-fluoro-benzaldehydes (reagent) were
obtained from PCR and used without further purification.
Ortho-chloro-benzaldehyde (reagent) was obtained from Fisher
and used without purification.
Para-chloro-benzaldehyde (reagent) was obtained from Aldrich
and used without further purification.
Ortho, meta, and para-bromo-benzaldehydes (reagent) were
obtained from PCR and used without further purification.
Ortho, meta, and ?paa-a-isaldehydes (practical) were obtained
from Aldrich and used without further purification.
Meta-tolualdehyde (practical) was obtained from Aldrich aid
used without further purification.
Para-tolualdehyde (practical) was obtained from Fisher and
used without further purification.
Para-nitro-be aaldehyde (practical) was obtained from Fisher
and recrystallized from ethanol and water.
Meta-nitro-3-Vitrostyrene (practical) was obtained from Aldrich
and recrystallized from ethanol and water.
Benzaldehyde (practical) was obtained from Fisher and used
Salicylaldehyde (practical) was obtained from Fisher and used
Para-hydroxy-banzaldehyde (practical) was obtained from Fisher
and used directly.
Meta-bydro.:.y-benzaldahyde (practical) was obtained from Aldrich
and used without further purification.
Para-nitro-phenol (practical) was obtained from Fisher and
used without purification.
8-chloroethyl vinyl ether (practical) was obtained from Fisher
and purified by distillation under vacuum.
FPSLr.ILT AND DISCUSSION
Synthesis and Chnistry of Ortho, Meta, and
Para (2-vinyloxy)ethoxy- nitro tyr ene s
A. Preparation of the Monomers
1. Synthesis of ortho and Para_ 2-vinylox)ethoxy --nitro-
styrenes.-- The method of Thompson was modified by lowering the reac-
tion temperature of the Thiele reaction to -50C. with an ice-methanol
bath. This may or may not have been a significant improvement. The
new method of work-up of the crude products, developed durin this
study, is a definite improvement and has res.'lted in higher yields of
purified product and significantly less decomposition. This new method
consists of rccrystallization of the products from methylene chloride-
ethanol at or below room temperature.
2. Synt-sis of meta-(2-vinyloxy)ethoxv-&-nitrostyrene.--
This co.epound was successfully synthesized, isolated, and characterized.
The compound was successfully obtained by varying only the method of
recrystallizatioa of the crude product. Due to the apparently high
reactivity of the vinyloxy group on this compound, it cannot be recrys
talli:zd front; a warm protic solvent. The desired compound was recrys
tallized from carbon tetrachloride below room temperature to give a
90 percent yield.
B. Cationic p 1_ i :-Liijions of Ortho, Meta, and Para- 2-vinyloxy)e thoxy-
-nitrcsty ren -
All monomers *;re found to polymerize in the presence of BF3
in a dry solvent under nitrogen at -780C. The polymers obtained were
yello. amorphous solids and were linear polymers as indicated by their
solubility in mcthylene chloride. The polymers were found to be only
sparingly soluble in acetone and insoluble in all solvents tested that
were less polar than acetone.
The infra-red sectra of the polymers lacked the 1620 aid 1640
cm absorptions typical of the monomers while the absorptions assigned
to the nitrovinyl moeity (1625-1640 cm ) were still present.
The apparent success of these selective c~tionic polymerizations
of the electron-rich pendant vinyloxy groups would secm to indicate that
such selective cationic polymerizatioas should be general in applica-
tion. The obvious requirement of such a system is that the electron-
poor moeity be unreactive toward carbonium ions.
The polymers of the meta and para isomers cross-linked in methy-
lene chloride upon r-action with sodimn ethoxide to give quantitative
yields of insoluble amorphous resins. The infra-red spectrum of the
cross-linked polymer of the para isomer gave no detectable nitrovinyl
absorpi:on while the corresponding meta isomer seemed to have sone
pendant nitrovinyl groups still intact.
C. Anionic Pojlmerizations of Ortho, MIeta, and PIara -2-vinyoxyLthoxy-
2-ni t ro s tyr en
The orthu isoatrr gave no ethailo incoluble product and -recovery
of monomer was almost quantitacive. ,Thic c'~-;rvatloan was expected in
view of the "och)o-effect" reported by Nash !nd Drueke.
The meta and para isomers both gave high conversions to ethanol
insoluble product. The resulting polymers were white powders whose
infra-red spectra indicated that the vinyloxy groups were yet intact as
indicated by the 1620 and 1640 cm- absorptions.
The polymers were found to for:a amber solutions in hexamethyl-
phosphotriamide (HMPA) and N,N-dimethylaniline, thus facilitating the
determination of intrinsic viscosities and purification by reprecipita-
tion. Unfortunately, these solvents deactivate cationic initiators and
thus are unsuitable solvents for cross-linking polymerizations with
Lewis acids. This solubility is probably the result of an interaction
between the non-'onded electrons on nitrogen (solvent) and the electron
deficient nitro group (polymer). The exact nature of this interaction
is not presently understood.
D. The Possible Existence of an Intramolecular Interaction and Six-
me mbered Rin_ Forcmation by, P ara2-(2-vinyloxi_)e t!hxy--_nitrostyrne
The infra-red spectrun of this compound was examined in detail,
both in the solucoion phase (CIH2C12) and the solid phase (Nujol mull and
KBr pellet). In all cases, its spectrum included a strong absorption
at L629 cm1 and a barely perceptible shoulder at 1640 cm-I for the
vinyloxy gro.p. The 1640 cm absorption was almost undetectable due
to the strong broad 1630 c.n absorption due to the nitrovinyl moeity.
The validity of the 1530 cm- ass n,-.I t was demonstrated by comparison
with i:he spectrum of para-methoxy- -nitrostyrene.
In order to demonstrate the validity of the 1640 cm shoulder
assignment, pLara-niLro-(2-vinyloxy)ethoxybelnzene was synthesized. This
compound is electronically similar to the compound in question and if
the ring-form exists in the 8-nitrostyrene, it should also exist in this
compound. The infra-red spectrum of this compound contains a medium
absorption-at 1640 cm. The spectrum of each compound is shown in Figure
4, page 61, and pertinent infra-red data of these aid other compounds
appearsin Table 5, page 62.
Assuming that the postulate of Brey and Tarrant, which states
that these two absorptions are due to the two rotational isoenrs of the
vinyloxy group, is valid, then the infra-red data obtained in this study
indicates that the ring-form is not the sole existing form of the mole-
During the course of this study, the H nnr spectra of the
three vinyloxyethoxy--i-nitrostyrenes, para-nitro-vinyioxyethox, .irene,
(2-vinyloxy)ethoxybenzene, a d B-chloro-ethyl vinyl ether were examined
in detail. The spectra of the vinyloxy groups, in particular, were of
interest. The geininal coupling constaits (J B), the cis coupling cons-
tants (JAC), and the trans coupling constants (JBC), and the chemical
shifts of the -protoas ( H ) were obtained. See Table 61, page 63.
The geminal coupling constant of para-(2-vinyloxy)ethoxy-3-
nitrostyrene (JAB = -2.2 hz.) is less than that of (2-vinyloxy)ethoxy-
benzene (JAB = -2.0 hz.) and eqjal to that of meta-(2-vinylo:xy)ethoxy-
3-ni;rostyrene (JAB = -2.2 hz.). This indicates that the degree of
resonance (or extent of mesoimcric contribution) existing in the para
iso.ner is approximately equal to that of the meta isomer and signifi-
cantly less than that in (2-vinyloxy)ethoxybenzene.
The .cis coupling constant for the para isomer (J = 7.0 hz.)
was higher than both the meta isom er (6.9 hz.) and the o:tho isomer
------------------'--- -- ~ -=
---___ ---_-_ -- -- -- -
'~-'- ---~ ----'IL-`----'--~ ~----
' -4 l
Pertinent Infra-red Data of Monomers, Polymers and Related Compounds
Coaipo und C=C C=C C=C
nitrovinyl vinyloxy aromatic
(cm- cmI) _____(cm
8. nuLnber I cationically
9. number 2 cationically
10. number 3 cationically
11. number 2 arionically
12. number 3 7nionically
13. number 9 cross-linked
14. number 10 cross-linked
1625 1620, 1640
1630 1620, 1640
Nuclear '!ay .itic Resonance Data from Some Vinyloxy Compouids
(CDC13, 60 Mc./sec.)
Compound THc JAC (hz.) JBC(hz.) JAB(hz.)
(cis) (trans) (gem)
B-nitrostyrene 3.42 6.9 14.0 -2.4
P-nitrostyrene 3.46 6.9 14.2 -2.2
,nitrostyrene 3.43 7.0 14.3 -2.2
ethoxybenzene 3.42 6.9 14.2 -2.4
(2-vinyloxy)ethoxybenzene 3.53 6.9 14.0 -2.0
$-chloroethyl vinyl ether 3.55 7.0 14.2 -2.3
Nuclear Magnetic Resonance Data from Some Vinyl Ethers*
R THc JAC (hz.) JBC(hz.) JAB(h n.)
t-butyl 3.72 6.2 13.2 -0.1
i-propyl 3.75 6.9 13.7 -1.2
cyclohexyl 3.87 5.7 14.7 -1.6
2-ethylhexyl 3.60 6.1 12.9 -1.8
i-butyl 3.56 6.3 14.2 -1.7
n-butyl 3.47 6.9 14.4 -1.8
ethyl 3.55 6.9 14.9 -1.7
methyl 3.62 6.6 14.4 -2.2
8-chio:oethyi 3.50 6.6 16.2 -2.7
*Data of Feeney and coworkers33
(Neat, 40 Mc./sec.)
(6.9 hz.) and eqial to that of the corresponding para-substituted-nitro
benzene (7.0 hz.). A similar trend was noted in the trais coupling
constants. The trans coupling constant for para-(2-vinyloxy)ethoxy- -
nitrostyrene (JB = 14.3 hz.) was the highest obtained for any of the
six compounds studied.
The chemical shift of the a-proton of the para isomer (T =
3.43) was quite similar to that of the corresponding nitrobenzene (T =
3.42) as -well as that of the ortho isomer (T = 3.42). At the same tine
it was significantly downfield from the corresponding signal of the meta
isomer (T = 3.46), vinyloxyethoxybenzene (1 = 3.53), and -chloroethyl
vinyl ether (T = 3.55).
These trends indicate that any possible contribution of the
ring conformation does not significa ltly affect the over-all degree of
resonance present. It also appears that the degree of oxoniun character
present in the phenolic oxygen in both the ortho and para isomers does
influence the degree of resonance via an inductive effect through the
two carbon saturated bridge. This would also explain why the vinyloxy
groups of Lhe orl:to and para isomers are so much less reactive toward
electrophilic attack (as evidenced by their stability in warm ethanol)
than the meta isomer.
The ultra-violet spectrum of the cationically initiated polymer
of the para iscnier was found to be quite similar to that of the parent
copoiund (see Figure 5, page 65). The absorption imaxima were at identi-
cal wavelengths and only the ;nolar absorption coefficients varied. This
agi:eeO well with the results of Thompson :who compared the spectrum of
the para is..i-r with the co:casposding para-(2--ethylcox)ethoxy-8-nitro-
styrenc. These results again give no indication of any introa.Iolecular
interaction in the vinyloxy compound.
-a -4 -I
/ Lr ,-s
o, o ... .. 0r.
1O I --
\C C3 o
^^ ^ s-^
*^ *< l'"
The results of these studies prompted the a jthor to examine
more closely some of the results aid conclusions reported by r;,,-, ,p-o:1.
Thompson has pointed out that the inductive effect across a saturated
two-carbon bridge is much less than across a one-carbon bridge. It
should be pointed out that the difference in pKa between acetic acid
and S-chlo:opoopionic acid (0.80) means that the Ka of the latter acid
is 6.3 times greater. In addition, the Ka of the latter acid is 7.6
times larger than that of propionic acid.
Perhaps a more pertinent comparison, for the purpose of gaining
some insight into the sensitivity of the vinyloxy group to inductive
effects, can be made by exailnieg the rates of acid catalyzed hydration
of certain viiyl ethers as both reactions involve a rate-determining
attack by al electrophile to produce analogous carbonium ions. Jones
and Wood have reported that the rate of hydrolysis of ethyl vinyl ether
-2 -1 -1
is 5.3 x 10 1. mole sec. while that of 0-chloroethyl vinyl ether
-2 -1 -L
is 0.44 x 10 1. nole sec. This data indicatesthat vinyl ethers
are quite sensitive to iaductive effects, even when -uch effects must
be traas-nitited across a -,aturated t.;o-carbon bridge.
This author considers the dipole moment data determined by
Thompson as evidence against the proposed ring-for:m. The reasoning
behind this statement may best be explained by considering para-(2-vinyl-
oxy)etho;:y-3-nitro, ;t;',.- i. as a di-subtituted ethylene glycol. One aay
thus consider the dipole moment of the compound to be the resultant
of the two vectors which in turn represent the "group moments" of the
If the vinyloxy gro.u is not involved in a ring-form, then
its time-average resultait position in space would require that the
angle between the two group moments be greater than 90, assumrig e'xtre':ely
hin.ier-d rotaLion between the phenyl oxygen, and about 1800 assuming
free rotation about that bond.
On t'he other hand, one would expect the angle between the two
group moments to be quite small if one assumes the ring-for-m. Th-;,
from a qualitative stand point, the resultant dipole moment of the ring-
fo:rm would be expected to be greater than that of the corresponding
ethyloxy coiapound vhile one would expect the linear-for.a to have a
dipole moanent less than the ethyloxy coupou-id. The dipole nmoient of the
ethyloxy compound is greater by 0.71 D.
In conclusion, the data obtained to date indicates that the
postulated ring-form, if existent, is not i-he sole existing form of the
molecule. The data, however, does not rule out an cqil-ibciu,.ra between
the liaeal-fo:-a and ring-forn. However, it would appea- that the induc-
tive effect of the partial oxoniumn, through the saturated two carbon
bridge, exerts the predominant effect on the physical aid spectral
properties of the molecule.
Studies of the Anionic Polymerization of Some
Other Mono-substituted g-nitrostyrenes
A. Synnthesis of Comouds
Fifteen substituted -nitrostyrenes and &-nitrostyrene were
synthesized for this study, all of which had been previously described
in the literature. All compounds were synthesized by the methods of
Thompson, however, rather than the various methods described for the
known conounds. For this reason the results of all syntheses were
described. In general the yields of purified monoier were poor, not
because of the method of synthesis but because of the method of recr)s-
callization -.hich nearly always involved hot or warm ethanol. In most
cases, the process of dissolving the crude product in hot ethanol was
accompanied by an undesirable side reaction which reduced some product
to an a-norphous white solid (probably polymer).
It is uAfortunate that the technique of recrystallization from
mnethylc-ne chloride and ethanol at room temperature (as described in the
synthesis of ortho-(2-vinylo::y)ethoxy-$-nitrostyrene) had not yet been
discovered. It is very likely that this technique would have resulted
in much lii b.r yields of purified monomer, particularly in the case of
the more polar compounds.
B. Kinetic Study of the Polymerization Rates
The method gravimetricc) used to determine the rates is less
than ideal. The major diadvantage is that rates of polymerization are
determined from precipitated product and the accuracy of the determina-
tion obviously relies heavily upon an essentially quantitative precipi-
tation of the product. Furthermore, when the percent conversions are
very low, a very small amount of polymer left in solution can be very
significant. Most of the polymers obtained during this study were
essentially insoluble in all coirnon organic solvents tested except DLF.
Of course, polymer solubility is dependent on molecular weight. The
solubility of lower molecular weight polymers is always greater. The
molecular weight distribution curves of polymer samples obtained during
this study indicate that molecular weights are extremely uniform as
indicated by the low values for M /M obtained (see Table 7 on page 70.
A notable exception to this was poly-meta, -dinitrostyrene. Low ratios
of M /M and narrow molecular weight distributions are typical for anionic
polymerizations in aprotic media where chain transfer and termination
are not occurring.
The elemental analyses of the polymers obtained during this
study appear in Table 8, page 71, and the melt temperatures in Table 9,
page 72. The polymers evidenced unexpected thermal stability. The
other assumptions incorporated in the kinetic treatment well be dis-
1. The rate of initiation is fast relative to prop0aation.--
Two fairly representative monomers, para-methoxy-g-nitrostyrene and
6-nitrostyrene, were quantitatively investigated in this respect. Para-
nethoxy-F-nitrot" Ln: in particular was studied because it : p ?rently
it > > C),
Sc 0. I
S*r o .
n3. rt 41
l "4 &
.A 0 0
O 0 cO
0 E) 0a
0 > 0
C) 0 -4
4 C Bo 0
cs r- C, Co rI C4 L' co
0o C) 0 C) C C)
on C C:) C) (D C) CD C)
C-l CD n') CD C) C) CD C)
Co 4 -4 C) c 0 C4 C1
o Ui u') C0 ) r- CD C) 0
-4 -4 o -o A
-U')* vo cm 14 L4 L' -4
S-4 o '0 CD o a T '
P4 .C4 p4 C.4 9 Pe- P4
'-4 ro4 4- r F. : 4
iS 4 o o o 4- W4-1
a: i r-- i- ** CS
;a 4 a a) (' C
eI P4 0 P4 I
rg c qj ^ '^ TO l c
i 00 1
I I I I I
- M+ c
I('J c4 O '-4 fr- -3- (3 o a rn cM 1 d 4
c0 0 4 r- \D (' O (4 i, r- 0' 0
o a' oo -f CY co 0 0 Cri a' c0 cn cIN
-4 '- '-4 CS a' r- .0 c-4 Cn c r(
110 'o0 'D \o 0 I'D U) L In Un ,ij- .Z -
I I I
'n -4 -4 a' -4I L-3
4-i 1-4 -4 -4 C, C
^-1r- rl l Cn e
c cc c0 r-4 r- coC cO o0 Ce I T- r
cn uI m o cc en cn c -0 '- 1- -4
fn Ln ir) '0 '0 r. -4 Ln V r-4 ,-4
4 cn m 0 o 0c cc a Ca
-Z 0 0 0 0 c r cn c-4 ('4 a' a
S .0 %.0 o oI, oI m-l crn
$-'f- X X N 0 0 0
.0 e 0 05 0 p N N
4-1 4 4 4- '- 3 -4 0 o 4: 4r
C) ) Ca) C) 4-4 -4 -4 N 1 .,- .^4
2 2 2 2 I 4-4 L4-" u f 0 c
P. f2 C 0 i Cl a. 2 m~ 2 Cl.
2hermal EB-hvior of Poly-substituted- -nitrostyrenes
Substituent Discoloration of Melt Temperature
Solid C. 0C.
H 300-305 (dec.)
meta-methyl 275-230 >300
para-methyl 295 >300
,neta-methoxy 290-295 (dec.)
para-methoxy 260 270--275 (dec.)
ortho-fluoro 285-295 >300
meta-fluoro 275-280 >300
para-fluoro 290-295 >300
para-chloro 285-290 >300
meta-broino 250--260 > 300
para-broino 280-293 >300
meta-nitro 290-295 (dec.)
para-nitro 290-200 (dec.)
is the least reactive of all monomers studied. It was felt that if
this monomer would "pass the test" then the assumption is probably
valid. The ultra-violet method used gave values for the rate constant
of initiation, k. = 2.9 and 3.5 1. mole sec. respectively, for the
para-methoxy and non-substituted B-nitrostyrenes (see Figures 6 and 7,
pages 74 and 75. These values indicate that the rate of initiation is
rapid and that the observed rate of polymerization, v is the rate of
2. The rate of chain transfer is small or non-existent.--
As previously mentioned, those polymers whose solubility in L:MF per-
mitted GPC molecular weight distribution analysis gave very narrow
molecular weight distributions (see Figure 8, page 76 for a typical
example). This. is one of the most surprising characteristics of these
polymerizations to be noted to date. The apparent lack of reactivity
of the propagating f-nitrostyryl carbanion toward ethanol can be ration-
alized on the basis of pKa values. The pKa of nitromethane is 11.0
while that of ethanol is 15.9. It can be seen that the structure of
the propagating '-nitrostyryl carbanion is quite analogous to that of
the conjugate base of nitromethane. From this data it can be seen that
the propagating carbanion is a Ear weaker base thai the ethoxide anioi.
3. Terminaition does not occur during the polperizations.--
The molecular weight distribution data also supports this assumption
except in the case of the meta and para- -dinitrostyrenes where a "back
biting" form of auto-termination has been proposed. This termination
also accounted for the broader molecular weight distribution curves for
the corr:sp:oiLng polym.-rs (see Figure 24, page102). In higher concen-
trations of polymer, intermolecular terinination is also likely.
II II II
H 1 -1
^0 00 0 O ^ C \
0 U 0
(D u p
- CO O
23 25 27 29
Molecular Weight Distribution Curve of Poly-para-
The fact that termination does occur for these monome.rs coupled with
the apparently significant solubility of the resulting polymers in the
chosen solvent system made it impossible to obtain a rate constant for
para- -dinitrostyrene. The validity of the value obtained for the
meta isomer should be questioned despite its excellent Hammett plot
agreement with that value obtained by Kamlet and Glover.
4, 5. The length of the poljymer chain does not affect the
rate of reaction. -- This assumption appears to be valid up to a point
as indicated by the kinetic plots (see Figures 6-15, pages 74 through
84 .) The "straight-line behavior" of the data indicates that this
assumption is valid for low conversions. As previously mentioned, the
polymerizations are heterogeneous after 10 to 25 seconds of polymeriza-
tion depending upon the monomer. This requires that, in order to main-
tain a constant rate of polymerization, the propagating carbanion must
maintain a constant access to monomer which becomes more difficult as
the length of the precipitating polymer occludes and effectively buries
the carbanion. This is the most probable explanation for the sudden
decrease in observed rates of polymerization at higher percent conver-
sion. However, the fact that the observed rates remain constant past
the point of heterogeneity does definitely sho.- that the mere precipi-
tation of product does not alter the kinetics of the reaction. This
observation validates assumption 5 as well.
6. Conversion of initiator to proaatin_.n carbanion is quan-
titative and the reactivity of all resulting ion_ -pairs is assumed to be
equal.-- The initiation reaction must be quantitative as evidenced by
the relatively high reactivity of n-nitrostyrenes toward nucleophilic
attack. This high reactivity is a-parent from Kanlet's observations.
1 0o1 0
o II L7 Q C%
O C. a) .
0.0 C'J 0
O m i r o
00 U) 'J 0
0 0 C 0
4X O 4 0
S-I- u O 0
00 0 r- O
0 i 0 0 -40 .
SC *4 4
4 4 -4
o -O 4 C r1
-4 O) 0 U.)
\ II -- t vo a
O 1 *-0 uL)
r N 40
.0 0 4
v *0 O
% o4-o1 1
(- O 0
r-4 4 r.
0 0 0o
o P4 0 -C
\c O u-i .Ho
&. II 4.)
\ 0 o a in
O a w
\ y a o (
\ m aSr;<
\I '- -
\4 bo -i
\ iu o UU
0 0 0
I. 0 ) O 0
N Ld o C iJ
0 0 0 0
o CU cM -1
\ s K4
r--4 c I0 x
ox CA L
0 -4 1--
0 ca 4 U
No OJ 0
0 0 0 0 0
0 0 0 0
O in en O
r~ CD o in 11 0O
~II_ __ I~
to 0 to 0 Ll
0 O 6 0
Propagation Rate Constants (k )
Substituent k (1. mole sec. ) k /k
p p o
para-methoxy 0.38 0.42
meta-methyl 0.57 0.63
para-methyl 0.63 0.71
-H 0.90 1.0
para-fluoro 1.1 1.2
meta-methoxy 1.3 1.4
para-chloro 0.73 0.82
para-bromo 1.4 1.6
meta-bromo 1.8 2.0
meta-nitro 2.2 2.5
The fact that polymer yield has been shown to be directly proportional
to initiator concentrations (see Figure 19, next page) supports the
assumption that the reactivity of all carbanions is essentially equal.
If there were significant quantities of both tight ion-pairs and the
more reactive solvent-separated ion-pairs, then one would expect a
dilution effect to result in an increased observed rate of polymeriza-
tion as has been observed in the aiionically initiated polymerization
of styrene in THF by Szwarc. This would be manifested by a decrease
of the slope of the percent conversion versus initiator concentration
plot. It should be noted that,in this work, this was only tested over
a fairly small range of concentrations (5-fold dilution).
7. The rate of plymerization equals the rate of disappearance
of monoimer.-- There were no indications during this study that any side
reactions occurred. In view .of the fact that possible base catalyzed
Michael addition of ethanol to B-nitrostyrene is merely an extreme of
chain transfer, this possibility need not be considered further in view
of the molecular weight distribution data.
The Ha3nett plot of the kinetic data (see Figure 20, page 91
showed a surprising resemblance to a similar plot of the data of Kamlet
and Glover, Figure 21, page 92 This fact alone illustrates the
mechanistic similarity between the base catalyzed Michael addition reac-
tion and the anionic polymerization of a, -unsaturated compounds. The
fact that both plots definitely show and unusual trend is certainly
reinforcing that an unusual effect is being observed and not merely
Non-.straight Hanmiett plots have been obtained before from many
organic reactions. However, these have usually been explained on the
"1 G) (U
. o. O cv 4. C, o
___~I__CI_ ~_ -I--~--L)----C------I II