Jan. 20, 1952
KINETICSOF POLYMERIZATION OF ALLYLESTERS
The acid chloride, 279 g. (2.31 moles), was added dropwise t o a mixture of 158 ml. (2.32 moles) of allyl alcohol, 371 ml. (4.6. moles) of pyridine and 500 ml. of toluene. The addition was completed in one hour and gentle reflux was maintained for an additional two hours. The reaction mixture was washed with 2 X 100 ml. water, 3 X 100 ml. 5% hydrochloric acid, 2 X 100 ml. 5% sodium hydroxide and again with 2 X 100 ml. water. After drying over 35 g. of calcium chloride and 15 g. of potassium carbonate, the ester was distilled under nitrogen. The product was collected at 13&140°, refractionated and collected a t 138.5-138.7’, n % ~1.4098. The yield was 155 g. (47.5% based on acid chloride, 44.6% based on acid). Isopropenyl acetate from theoTennessee Eastman Co. was distilled and collected at 96-97 . Benzoyl peroxide was purified by precipitation with methanol from chloroform solution and with distilled water from acetone solution. Experimental Procedure.-A solution of benzoyl peroxide in the monomer was transferred by means of a hypodermic syringe to Pyrex tubes with constricted necks. The tubes
[CONTRIBUTION FROM THE INSTITUTE OF POLYMER
Allyl Polymerization.
337
were cooled in a Dry Ice-methanol-bath and evacuated on a Cenco-Hyvac oil-pump and then flushed with pure, dry nitrogen. Alternate evacuations and nitrogen flushings were repeated several times after which the tubes were seated under vacuum. The tubes were suspended in a rocking wire basket in a constantotemperature bath of paraffin oil maintained a t 80 f 0.1 At measured intervals tubes were removed and dipped into the freezing mixture. The tubes were opened and samples were removed by hypodermic syringe for determination of peroxide concentration. The concentration of benzoyl peroxide in the allyl esters was determined by iodometric titration in glacial acetic acid after addition of potassium iodide according to the method of Bartlett and Altschul.‘ The concentration of peroxide in isopropenyl acetate was determined by back titration of excess arsenious oxide with standard iodine according t o the method of Siggia.lV
.
(19) S. Siggia, “Quantitative Organic Analysis via Functional Groups,” John Wiley and Sons, Inc., New York, N. Y.,1949, p. 102.
BROOKLYN, NEWYORK
RESEARCH, POLYTECHNIC
RECEIVED FEBRUARY 13,1951
INSTITUTB OF BROOKLYN]
111. Kinetics of Polymerization of Allyl Esters1B2
BY NORMAN G. GAY LORD^ AND FREDERICK R. EIRICH The peroxide-catalyzed bulk polymerization of allyl esters, attended by the phenomenon of degradative chain transfer, may also be accompanied, t o a small extent, by secondary reactions, wherein hydrogen abstraction from the acid derived portion of the ester or afree radical displacement reaction occurs. The extent of these reactions determines the dew-of further lowering of the DP beyond that brought about by the primary degradative attack. The following order of DP is found in the allyl esters: trimethylacetate < propionate < acetate < ethyl carbonate. A kinetic scheme is set up including these secondary reactions and the conditions under which it yields the experimentally observed constant dM/dP are discussed. The polymerization of isopropenyl acetate with benzoyl peroxide is almost identical with that of allyl acetate, the shift in the position of the ester group apparently producing little change in polymerization behavior. The reciprocal relation between DP and rate of BaO2 decomposition may be traced t o a common cause, Le., the relative ease of transfer re actions on allylic molecules.
The benzoyl peroxide catalyzed bulk polymeriza-
tion of allyl acetate a t 80’ yields a polymer with an average molecular weight of about 1300.‘ In any given polymerization, the concentration of monomer polymerized is, to a good approximation, a linear function of the concentration of peroxide decomposed, ;.e., dM/dP is constant. The constancy of dM/dP is attributed to degradative chain transfer‘ wherein active radicals, as in growing chains, yield stabilized radicals with lowered reactivity by abstraction of a-methylenic hydrogen from the allylic monomer. Emulsion polymerization of allyl acetate with potassium persulfate gives a polymer of the same average D P as in bulk polymerization indicating analogous initiation and termination mechanisms.s In previous paperss it was shown that the decomposition of benzoyl peroxide in allyl alcohol, allyl bromide and several allyl esters was compatible with the existence of a spontaneous unimdecular reaction accompanied by a free radical induced (1) This work was carried out with the support of the U. S. Navy, Bureau of Aeronautics. (2) Abstracted from P portion of the dissertation submitted by Norman G. Gaylord t o the Graduate Faculty of the Polytechnic Institute of Brooklyn, in partial fulfillment of the requirements for the degree of Doctor of Philosophy, June, 1950. (3) E. I. du Pont de Nemours and Co., Yerkes Research Laboratory, Buffalo, N. Y. (4) P. D. Bartlett end R. Altschul, THIS JOUXNAL, 67,816 (1945). (5) P. D. Bartlett end K. Nozaki, J . P d y m c t Sci., 8, 216 (1948). (6) N. G. Gaylord and F. R. Eirich; Part I, THIS JOURNAL, 78,4981 (1951): Part 11. iMd., 74,534 (1952).
chain decomposition. The present investigation is concerned with a study of the kinetics of the benzoyl peroxide catalyzed polymerization of allyl esters. Experimental Results The bulk polymerization of several allyl esters was carried out under vacuum a t 80°, in the presence of varying initial concentrations of benzoyl peroxide. The concentrations of monomer and peroxide were followed as a function of time. Unsaturation and peroxide concentration were determined by the methods of Bartlett and Altschul.* The results are summarized in Table I wherein the concentrations are expressed in moles per k i l ~ g r a m . ~The constant value of dM/dP in a given run and the variation of this value with initial peroxide concentration are shown in Fig. 1.
Discussion Secondary Degradative Attack-As indicated by Bartlett and Altschul‘ there are two possible positions in allyl acetate from which hydrogen atoms might be removed to yield a free radical with greater stability than the attacking radical. Bartlett favored reaction 1 and rejected reaction 2 on the grounds that vinyl acetate which can undergo the second reaction but not the first, polymerizes to long chains with no appearance of degradative chain transfer, while allyl propyl
VOl. 74
SORMAN G. GAYLORD AND FREDERICK K. ETRICII TABLE I POLYMERIZATION OF ALLYL ESTERS WITH BENZOYL PEROXIDE AT SO =t0.1 Peroxide (m./kg.)
Time, hours
Monomer (m./kg.)
Polymer,
Peroxide
c70
(m./kg )
Monomer (m./kg.)
Peroxide (in /kg 1
Polymer,
5%
Polymer,
Monomer (m :kg )
76
A . Allyl acetate
9.79 8.80 8.40 7.40
BzzO?,9.96%
BznOi, 4.91'7,
BzrOn, 2.05%
0.0845 .0517 .0316 ....
0.0 2.50 5.00 24.00
0.0 10.1 14.2 24.4
0,204 ,115 .Of369
9.50 7.69 6.73 5 17
....
0.0 36.9 52.1 68.5
8.93 5.63 4.28 2.81
0.411
0.0 19.1 29.2
,198 ,109
I, 5i,
T3. Allyl propionate HZnO,,9.52%
HzrOn, 4.9457,
n ,204
0.0 8.3 12.:3
0.0 2.50 5.00 24.00
,113 0538
21.1
. . . ,
BaOz, 2.02%
0.0836 .Os23 .0334
24.00
i
.
.
.
7.57 6.69 6.19 4.74
%:Or,
0.0 11.6 18.2 37.4
0.204 .119 ,0727 D.
0 . 0859 ,0445 .0240
2.50 5.00 24.00
. .
0.0 27.4 40.6 60.3
0.370 .190 .I06
0.0 32.9 49.5 70.2
7.75 5.20 3.91 2.31
...,
BzzOz, 8.96%
0.0 40.8 57.4 74 0
7.05 4.17 3.00 1.83
....
Allyl trimethylacetate RmOz, 5.05%
6.84
0. 0
6.14
10.2 17.0 22.7
5.68 3.29
0.393 ,183 . OS23
4,94$>
7.51 5.45 4.46 2.98
....
BzzOz, 2.08%
0.0
0.0 16.8 27.5 45.9
Allyl ethyl carbonate
C
0.0 2.50 5.00
8.25 8.86 A . 96 4.46
0.20s .lo25 ,0520 ....
6.70 5.16 4.30 3.57
0.0 23.0 35.9 46.7
E. Tsopropenyl acetate Bz&, 2.G1 Yo
0.0830 ,0501 .030s
0.0 2.50 5.00 48.00
I
I
.
.
9.7s S 92 8I5 7 13
BzzO?, 4.95%
0,205
0.0 8.8 1:3,G
OB13 . .
27 1
0
8.0
g
0.0 18.4 27.8 48.9
carbonate which would undergo the first but not the second reaction shows a constant dM/dP.
I
10.0
9.43 7.70 (i .83 4 81
,112
R. 6.0
It + CHz=CHCHrOCCH3 + 0
c!
I/ + CH*=CHCHOCCHa
RH
$ 4.0
r,
t o
Y
c
2.0
(1 1
I1
.CH?CH=CHOCCHl
Wi
0 il "
R.+ CIT+2HCIj?OCCHB
---f
0 RII
1 + CHQ=CHCH,OCCHX. f
4
(2)
0.
;
CF-Ig=CHCHgOC--CH?
c .
1 O Z
1L-J
i - L - l L L i i L _ l L i
_i
D L
O 10 O 20 0.30 0.40 0 10 0.20 Peroxide, moles per kilogram
L
L
L I-
O 30 D I O
Fig. 1.-Monomer concentration plotted against peroxide concentration in bulk polymerization of allyl esters at SO ': A, allyl acetate; B, allyl propionate; C, allyl ethyl carbonate; I), allyl trimethylacetate Data from Table 1. upper curve, 2% B z ~ O Z ;middle curve, 5% RzlO?; lower curve, 10% Bz&
summary of constants obtained in the bulk polymerization of several allyl esters in the presence of benzoyl peroxide a t 80" is given in Table TI along with some of the data of Bartlett and Altschul. The relatively small variation in the results supports Bartlett's contention that hydrogen abstraction from the methylene group alpha to the double bond is the primary source of degradative chain transfer, It is difficult to see, however, how n kinetic scheme formulated by the use of
Jan. 20, 1952
KINETICSOF
POLYMERIZATION OF
ALLYLESTERS
TABLE I1
SUMMARY OF CONSTANTS FOR ALLYLESTERSBY
Initial wt peroxide,
.
Monomer
Allyl acetate
CeHsCOO.
%
m
2.05 4.94 9.96
12.2 12.6 12.1 12.3
Allyl acetate'
CeH~C00-00CCaHs P
POLYMERIZATION OF BENZOYL PEROXIDE AT 80 & 0.1 O THE
1.01 2.14 6.10 9.95
dM dP
Conversion,c %
25.5 20.8 15.2
26.1 46.1 69.4
12.0 25.2 49.0 70.9
22.2 15.5 12.3
21.1 45.9 72.1
P
+ CH2=CHCHzOCOCHa --+ M
P
CeHsCOOCHzCHCHnOCOCH. Ri CeHbCOO.
+ CHz=CHCH*OCOCHs + kb
M
P
C01
28.8 24.4 18.5 15.6
ki + 2CsHeCOO* ka
0.3
13.5 13.6 14.1 14.0
+ CeHsCHzCHCHnOCOCHs RI
CeH6COO. P
+ CH2=CHCHgOCOCHa + kc
M CeHsCOOH
CHFCHCHOCOCH~ r ks
13.7 f 0.4b Allyl propionate
1.97 4.94 9.52
10.3 10.6 9.9
+ CHz=CHCHzOCOCHs +
CsH6COO~
14.3 14.0 14.7
C~HKCOOH CHz=CHCHzOCOCHI* Y
27.7 24.1 14.5
38.3 62.7 74.1
2.08 5.05
5.6 5.3
M R
2.01 4.95
12.6 12.4
+ CH-CHCHsOCOCHs
18.7 15.7
+ RH
23.7 47.5
r
R 25.1 18.6
27.1 48.9
reaction 1 alone could serve as an explanation for the small but significant deviations which are observed within the series of allyl esters. These variations appear to be indicative of the extent to which these compounds can and do participate in reaction 2 as well as reaction 1. Independent support for this possibility is found in the result of Matheson, et dI7 that chain transfer in the methyl group of vinyl acetate is about forty times as frequent as that occurring in the side methyl of methyl methacrylate.s Further, in the peroxide-catalyzed polymerization of vinyl acetate the= is < 600 and as many as 100 or more transfer reactions per kinetic chain are i n d i ~ a t e d . ~Similarly, the criterion of a constant d M / d P for reaction 1 is not compelling since a mechanism leading to a constant dM/dP can be equally formulated if reactions 1 and 2 coexist. Considering the original scheme of degradative chain transfer, and adding the steps involved in the additional transfer reaction 2, we have (7) M. S. M a t h w n , E. E. Auer, E. B. Bevilacqua and E. J. Hart, THISJOURNAL, 71, 2610 (1949). (8) H. Kwart, H. S. Bmadbent and P. D . Bartlett, ibid., 73, 1080 (I%@, ham obtained a lower value for the chain transfer constant for vinyl acetate, not in good agreement with that of other
+ CHt=CHCHOCOCH*
kc
+ CHz=CHCHzOCOCH3 + M RH + CHz=CHCH~OCOCHI* Y
12.5 0.1 Data from Bartlett and Altschul, ref. 4. DP obtained from Staudinger's equation after calibration with two samgles of M = 890 and 1150, determined cryoscopically. e 48 ours.
workers,
Rn+1 k3
M
5.45 f 0.15 Isopropenyl acetate
+ CHs=CHCHzOCOCH3 +RCHzCHCHzOCOCHs kz
Rn
1 4 . 3 f0 . 2 Allyl trimethylacetate
M
P
10.3 f 0 . 2 Allyl ethyl carbonate 2.02 4.94 8.96
339
k6
r+r+r-r
ks ? + Y + Y - Y
ki r+Y+r
-
Y
By steady state assumptions we have -dM/dt = (ka k b dp/dt = 2k1P - (ka
+ + kd) P M + (kz + ka + k4)RM ko
kc
kb
+ kd) pM = 2k1P
P
=
2k1P
+ + k, + pM - (ks + k4)RM E 0
F~ where k o
dR/dt = (ka f
kb)
- k" pM E 0
= k.
kb
kd
Therefore = &Po
-dP/df
and
Although this mechanism is undoubtedly an oversimplification, it enables us to obtain an over-all picture of the situation.I0
-
(9) This k~ I/; kl of Bartlett and Altschul, ref. 4, and, as in their scheme, does not include induced decomposition, (10) As pointed out by the Referee, inclusion of R R + RI in the genetal scheme does not necessarily affect the ultimate kinetic picture since the D P data represent statistical averages and do not deny the presence of some molecules considerably larger than the mean,
-
+
NORMAN G. GAYLORD AND FREDERICK R. EIRICH
340
Vol. 74
would have resulted as from allyl acetate and the conversion would have had to have the same low order. Therefore, the presence of different, more reactive radicals, undoubtedly -COCHCl, are indicated. These are capable of starting new chains and are effective carriers, hence consuming more monomer, in contrast to the product from the acetate which is relatively ineffective as far as chain propagation is concerned. Degradative Displacement Reaction.-If the results from the polymerization of allyl trimethylacetate are examined, a striking incongruity is observed. From Table I1 it is seen that this compound which has no abstrac table hydrogen in the acid derived portion of the molecule, and hence only the allylic position available for degradative attack, nevertheless has the lowest E and the smallest dM/dP of all the allyl esters. Either allyl trimethylacetate presents a special case or a new mechanism must be postulated which will account for the behavior of the trimethylacetate within an over-all picture of the allyl esters. The lowered DP a t approximately the same conversion is indicative of a greater number of radicals, either from the catalyst, or by effective chain transfer, or may be due to more transfer relative to propagation. The lowered dM/dP may arise by wastage of initiating centers lowering the conTABLE I11 sumption of monomer per unit center, or may arise VISCOMETRY IN ALLYLESTERS from chain transfer to radicals which cannot propaPeroxide, Convergate the chain. From Part I1 of this series we Temp., Time, moles/ Polymer, sion, learn that the decomposition of benzoyl peroxide Monomer hr. kg. ?sp/c % in the trimethylacetate is more rapid than in the 0.04Sb 14.7 Allyl acetatea 75 4 0.173 other esters. This may also be indicative of the .O5lb 7 . 9 15 4 .175 presence of more radicals assisting in inducing Allyl chloroacetate' 75 5 ,0366 .047b 15.4 decomposition, Le., of more transfer to peroxide. 75 5 .0354 .069* 16.9 The structure of allyl trimethylacetate reveals 8.3 15 5 ,0354 .03Tb the possible origin of a radical which may be an 15 4 ,0361 .03@ 7 0 effective carrier, ie., the trimethylacetate radical. Allyl acetate 80 48 .0845 .047 This radical might arise by a free radical displace60 48 .204 .048 ment on the carbonyl as has been shown to occur 80 48 .411 .037 in the decomposition of oxalyl chloride, initiated Allyl propionate 80 48 .0814 ,036 by organic peroxides.12 However, a more likely 80 48 .204 .041 reaction would be a displacement at the allylic 80 48 ,393 ,039 carbon. Kharasch has shown that in the decom.032 Allyl trimethylacetate 80 48 .0859 position of acetyl peroxide in allyl bromide the free .033 80 48 .208 methyl radical attacks the allyl bromide, displacing .047 Allyl ethyl carbonate 80 48 .0836 a bromine atom and forming butene. Further, 80 48 .204 .046 other products isolated in the reaction were postu.059 80 48 .370 lated as arising in a similar manner.1g Finally, the Isopropenyl acetate 80 48 ,0830 ,050 induced decomposition of benzoyl or acetyl per.203 .047 80 48 oxides has to be considered as a radical displacea Data from Cohen, et al.," using benzoyl peroxide and ultraviolet light. The polymer was not isolated; qap/c ment reaction which frees acyl radicals. Thus a was determined at 30' from the increase in viscosity of the free radical displacement reaction a t the allylic product and value of per cent. polymer obtained by titration. carbon is a likely reaction. The trimethylacetate radical then can arise by a variety of displacement that the DP obtained from allyl chloroacetate reactions either in the monomer on the allylic must be of the same low order of magnitude as that carbon or in the polymer on the side chain. It of the other allyl esters. At the same time it was may then decompose to the t-butyl radical either found that the conversion is much higher for a given spontaneously or a t the moment of reaction. In amount of peroxide. If no degradative attack by order to include these features in a kinetic scheme reaction 2 had occurred or if this degradative leading to the experimentally observed constant attack had removed the chlorine, the same radical (12) M. S. Kharasch and H. C. Brown, THISJOURNAL, 64, 329 On the basis of the above kinetic scheme we are in a position to discuss the experimental data summarized in Table 11. Reaction 2 of the degradative chain transfer leads, in allyl acetate, to the radical -0COCH2. stabilized by resonance through the carbonyl group. In allyl propionate the corresponding radical -0COCHCHs would be similarly stabilized, while in allyl ethyl carbonate, as in all allyl carbonates, no radical stabilization by the carbonyl group is possible. Thus, in kinetic terms, there is less degradative chain transfer in the and consequently a somewhat higher carbonate DP. Further, more monomer is consumed per given initiating radical, ;.e., fewer active radicals are wasted by termination in degradative attack, so that a higher dM/dP ensues. A slightly higher conversion follows. By similar reasoning, more degradative chain transfer would occur in the propionate than in the acetate due to the greater stability of the radical formed in the propionate, as borne out by the data of Table 11. Further evidence in favor of degradative attack in the acid derived portion of the ester, in particular on a methylenic hydrogen adjacent to carbonyl, can be observed in the work of Cohen, et al., on allyl chloroacetate. l 1 While no molecular weights as such were determined, sufficient values of qsp/c were calculated so as to show (Table 111)
O C .
(11) S. G. Cohca, B. E. Ostberg, D. B. Sparrow and E. R. Blout, J . P d m n Sci., 8, 264 (1948).
(1942). !la) M. S. Kharasch and G. Buchi. J. Org. Chcm., 14, 84 (1949).
Jan. 20, 1952
KINETICS OF POLYMERIZATION OF ALLYLESTERS
34 1
dM/dP, we can make several changes in the previous scheme. Replacing allyl acetate by allyl trimethylacetate, equations for k ~ k., , kb, k,, k ~ k~ , and kt, remain essentially the same. The equations for k d and kq are replaced by the radical displacement reaction
in this way. It may be concluded that, as already mentioned by Bartlett,I4 effective chain transfer is a regular feature in allyl polymerization although particularly pronounced in allyl trimethylacetate and in allyl chloride. It is apparent that experimental inaccuracies do not permit distinction between two mathimatical functions which do not diverge very greatly.16 kd' CsHsCOO* 4-CHPCHCH~OCOC(CHJI + While we believe that with regard to the extent P M to which radical displacement occurs, allyl triCHfCHCHzOCOCsHs (CH:)zCCOO* methylacetate represents a special case, the mechS MI anism as such cannot be excluded for the other k4' allyl esters. The final decision can only come from R CHpCHCH*OCOC(CH:)( a careful analysis of reaction products, but the fact M Pin trimethylacetate is exceptionally CHFCHCHPR (CHa),CCOO* that the D low indicates that only in this case do we have an M2 S Expressions for the disposition of the trimethyl- appreciable effective chain transfer from the acid derived portion of the molecule.16 acetate radical replace kaand k,. Polymerization of Isopropenyl Acetate.-The krs constancy of the ratio dM/dP observed with other (CH,)aCCOO. CHFCHCH,OCOC( CHI)&+ allyl esters is equally obtained with isopropenyl S M (CH&CH COa CH+-CHcHOCOC( CH& acetate (Fig. 2). The similarity of the polymerization of this monomer to that of allyl acetate has r been reported." Examination of the constants kib obtained in the bulk polymerization of this material (CH:)aCC00. CHpCHCH%OCOC(CH:), --f (Table 11) confirms these observations. Further, S M as pointed out in Part I1 of this series,6 the decomCHFCHCH~C( CHI): COS (CHa),CCOO* position of benzoyl peroxide in the course of the Mi S I n the steady state
+
+
+
+
+
+
+
+
-dM/dt
(ka
+
+ + kdpM + (kn + ka)RM + kcsM - (k. + + ko + kd')pM S 0 kb
dp/& = 2k1P
kb
:$:where dR/& = (k.
ko = k. -k
kb
-k k ,
kd*
+ &a) pM - (k: f k4')RM S 0 5.0t
I
,
I
,
0.05 0.10 0.15 0.20 0.25 Peroxide, moles per kilogram. Fig.2.-Monomer concentration plotted against peroxide concentration in the bulk polymerization of isopropenyl acetate a t 80": upper curve, 2% BZZOZ,lower curve, 5% BaOo. Data from Table I.
It should be pointed out that if the following propagation step (chain reinitiation) were included in the kinetic scheme (CHt)aCCOO* M -C Re the constancy of dM/dP would be interfered with. As a matter of fact we have observed that in many cases the data from allyl polymerizations can be fitted as well into a vinyl kinetic scheme. For example, a linear relationship between log M and
propionate > acetate > ethyl carbonate, D P and d M / d P decrease in the same order from right to left. If chain propagation (R. and ka) is more difficult going from right to left in the above monomer series, radicals may react instead with peroxide to induce wastage, increasing dP/dl and lowering dM/dP with monomers on the left. The necessary trend in ka would be that expected from steric effects. Similarly, if propagation becomes more difficult from right to left, but degradative chain transfer (kb and ka) is relntively unchanged from monomer to monomer, then w u l d be decreased going from right to left. Also. if propagation becomes more di5cult. then a transfer reaction with peroxide could become important, giving a lower s a n d dM/dP and a higher dP/& going from right to left. (17) R. Hart and G. Smets, J . Polymer Sci., I, 55 (1950); N. 0. Gaylord and F. R. Eirich, ibid., 6,743 (1950).
-
~ T Y R O N H. WILT
polymerization of both materials is also similar. Therefore, isopropenyl acetate can be considered as fitting into the same general position in the series of allyl esters as allyl acetate. The reactivity of the double bond would be approximately the same, since Melville and Robb18 have. shown that there is little difference in reactivity whether substituents are on carbon 2 or 3 . Primary degradative chain transfer in both compounds is comparable, the increased accessibility and decreased steric hindrance of the side methyl apparently balancing the decreased stability of the primary allylic radical as compared to the secondary allylic radical in allyl acetate.
Experimental Materials.-The allyl esters and benzoyl peroxide were prepared and purified as described in Part I1 of this series.6 Experimental Procedure.-Polymerizations were carried out as previously described. Samples were removed for determination of unsaturation and peroxide concentration. The analytical methods employed for the allyl esters were (18) H. W.Melville and J. C . Robb, Proc. K o y d Soc. ( L o n d o n ) , Ai96, 494 (1949); i b i d , 8208, 181 /19',0)
[CONTRIRUTIOY NO
82(1 FROM
Vol. 74
similar to those of Bartlett and Altschul.4 The bromatebromide solution used was standardized against the allyl monomer under investigation. The concentration of monomer in isopropenyl acetate was determined by removal of residual monomer under vacuum a t room temperature to constant weight. Isolation of Polymer .--The polymer was isolated by removing all volatile material under vacuum a t room temperature to constant weight. Purification of Polymer for Molecular Weight Determinations.-The polymer from the polymerization of the monomer to the exhaustion of peroxide was isolated as above, dissolved in benzene, extracted with aqueous potassium carbonate, dried and isolated as described by Bartlett a n d Altschul. Molecular Weight Determinations.-All molecular weights were determined cryoscopically. A solution of the polymer was made up accurately by weight in benzene and transferred to the apparatus for the determination of molecular weights by freezing point depression (Eimer and Amend) utilizing a Beckmann thermometer and mechanical stirring. The values of the freezing point depressions thus obtained were in each case the result of at least two checking determinations. Viscometric Determinations.-Viscosities were measured in benzene as solvent using a modified Ostwald pipet, in a constant temperature bath operating a t 27". BROOKLYU 2 . N. U RECEIVED FEBRUARY 13, 1%51
1FIC n R P A R T V F h ? OF CHEMISTRY, IJUIVRRSITY O F PITTSBURGH]
The Direct Pyridylethylation of Active Hydrogen Compounds. I. 2-Vinylpyridine with Ketones ROBERT LEVINE.4ND
?rlYRON
H.
WILT
The Michael condensation has been effected between a number of ketones and 2-vinylpyridine in the presence of sodium metal as the condensing agent In the pyridylethylation of methyl ethyl ketone and methyl isobutyl ketone, condensation occurs a t the 0-methylene group of the former and the a-methyl group of the latter compound.
While the ketones, acetonel and acetophenone? have recently been condensed with 2-vinylpyrihave been pyridylethylated indirectly by the reac- dine, a we are reporting the results we have obtained tion of the sodium derivatives of ethyl acetoacetate in similar condensations with a number of other ketones. Most of our condensations have been effected by v3 the interaction of two equivalents of ketone, one -CI-T--CFI? + CJT cocrwo?c,rr,+ equivalent of 2-vinylpyridine and a small amount of I sodium metal. The yields and other pertinent data on the compounds we have prepared are found in Table I. It may be seen that acetone has been pyridylethylated in negligible yield. Instead, 11, 70T it has been self-condensed to give a mixture of mesityl oxide and isophorone. The other ketones have been mono-2-pyridylethylated in fair to good yields. Furthermore, it may be seen that in the 111, 9oc, experiments with methyl ethyl ketone and methyl h'i isobutyl ketone, the respective dehydrated ketols I + c I I ~ c o c s 3 I ,+ 111, 3or, were also formed. In several of the runs, after the and ethyl benzoylacetate with 4-vinylpyridine and inonopyridylethylated derivatives were distilled subjecting the condensation prntlucts to hetiinic iroin the reaction mixtures, higher boiling nitrogencleavage, the direct pyridylethyhtioii of the sodium derivatives CJlJC'OCTT CTic CII 'i 9 C 11,' ic'rI--cIT CH$OCH(CH2CH&'y-2)CH(CH3)2 (VI of these ketones has Condensation a t the CH2 group not been reported previously. The three equations above show how ous materials were isolated, which probably conphenyl ~-(2-pyridyl)-propylketone may be pre- sist of condensation products of one molecule of pared by these two routes. Since the relatively re- the ketone(s) with more than one molecule of vinylactive ketones, phenylacetone and desoxybenzoin, pyridine. From the pinacolone run, both monoand di-2-pyridylethylated products have been iso(1) Doering and Wed, THISJ O U R N A L , 69, 24F1 (1947 I -J
f
(2) Boekelheide a n d Agriello. r h d , 72, 5 f l O i (1950)
7 ) R ~ i ~ k v i h e i dand e Rla'oii c b r d , 73. 2356 (1951)
