IONIC TELOMERIZATION OF STYRENE
May 20, 1954 [CONTRIBUTION KO. 337
FROM THE
2685
CHEMICAL DEPARTMENT, EXPERIMENTAL STATION,E. I. DU PONTDE XEMOURS COMPANY]
AND
The Ionic Telomerization of Styrene BY DONALD D. COFFMAN AND EDWARD L. JENNER RECEIVED DECEMBER 28, 1953 The ionic telomerization of styrene with acetic acid has yielded the acetates of alcohols containing from one to several styrene units, H(CH?CHPh),OAc Esters containing 1, 2 and 3 units have been isolated. From styrene and acetonitrile, acyl derivatives of primary amines having a number of styrene units have been obtained, and amines from the first two members have been identified, Similarly, styrene and formaldehyde in acetic acid have given the acetates of glycolq containing one methylene group and a variable number of styrene units.
The telomerization of an ethylenically unsaturated monomer, M, yields a family of products of the type A-M,-B in which n is a small integer and A and B are derived from reactants other than the monomer. The literature records such telomerization brought about by free radicals' and by ionic2 catalysts. The present investigation is concerned with acid-catalyzed telomerization in which the intermediates are cationic as represented schematically in the following steps
+ M +A-Mf A-M+ + M +A-M-M+ A-M,+ + B e +A-M,-B A+
Initiation Propagation Termination
The compound A-B may serve as the source of A' and B3,although this is not necessary. B may be a neutral molecule and thus require, as an additional step, the loss of a cation (for example, a proton) or the addition of an anion. In this work, styrene was employed as monomer, and A and B were
lyst. Among the catalysts investigated, perchloric acid was the most active. Sulfuric acid was approximately as active as the boron fluoride-acetic acid complex (Table I). TABLE I COMPARISON OF CATALYSTS FOR THE IONIC TELOMERIZATION OF STYRENE WITH ACETIC ACID Molar concn. of catalyst in acetic acid
Reaction time, hr
Total conversion,Q %
Yield of telomer, = 2 , "c
n
0.1 HC104 5 87 25 0 3 HI SO^ 65 84 28 0.27 BFS'CHjCOOH 65 72 18 a Total conversion was calculated as the weight of the total product divided by the weight of the styrene charged.
The boron fluoride-acetic acid complex was generally chosen for use to avoid the hazards accompanying the use of perchloric acid and to avoid the possibility of sulfonation which might occur with sulfuric acid. In a telomerization a t 25' with a A B 20-hour reaction time and 0.5 M boron fluoride1. H @ OAc9 acetic acid complex as catalyst, the product had 2. H e CH,CN (followed by OAce or H S 0 4 9 ) the following molecular weight distribution: n = 1, 3. HOCHze OAce 11%; n = 2,38%; n = 3,20%; and n > 3,31%. These combinations lead, respectively, to the ace- These fractions contained low proportions of hytyl derivatives of alcohols, amines and glycols drocarbon impurities. The fraction containing each containing from one to several styrene units. two styrene units was selected for detailed investiTelomerization of Styrene with Acetic Acidgation. This fraction was composed of the teloFrom a family of telomers, one ( n = 2 ) was se- meric ester (90%) and styrene dimer (10%). The lected for determination of structure. hydrocarbon was separated by distillation ; its concentration in the product was estimated from CeH6 the refractive index. I H( CHzCH) OAC Telomerization of Styrene with Acetonitrile.This telomer was demonstrated to be the acetate The telomerization of styrene with acetonitrile of 1,3-diphenylbutanol by hydrolysis to the alcohol offers a route to aliphatic primary amines having which in turn was oxidized to P-phenylbutyrophe- phenyl groups attached to alternate carbon atoms none identified by its melting point and those of its in the chain. By analogy with the products oboxime and phenylhydrazone. The formation of tained from styrene and acetic acid and also from 1,3-diphenylbutyl acetate can be accounted for consideration of the established synthesis of amides by (1) the addition of a proton to the P-carbon of a from the reaction of olefins with nitrile^,^ the telstyrene molecule followed by (2) the attack of the omerization probably proceeded through an inresulting carbonium ion on the p-carbon of a second termediate enol sulfate or acetate I11 which was styrene molecule, and ( 3 ) termination by the addi- hydrolyzed to the amide. tion of an acetate ion to the carbonium ion. This C6Hs '&Hs reaction is analogous to the previously described RCN I @ H(CH2JH),@ + H(CH2CH),--N=C--R telomerization of butadiene with acetic acid.2 I I1 The telomerizations were conducted a t 25' by adding styrene to an acetic acid solution of the cataCeHs OSOIH (Or OAc) (1) T. A. Ford, W. E. Hanford, 5. Harmon and R. D. Lipscomb. THISJOURNAL, 74, 4323 (1952); J. Harmon, T.A. Ford, W.E. Hanford and R. M . Joyce, ibid., 71,2213(1950): R.M.Joyce, W. E. Hanford and J. Harmon, ibid., 70, 2529 (1948): M. s. Kharascb, E. V. Jensen and W. H. Urry, ibid., 69,1100 (1947). ( 2 ) Ii. 1. Tenner and K . S. Schreiber, ihiii., 73,4 3 4 8 (1051).
I1
HS048 or
OAce
I
H(CHzCH)n-N=C-R
I11
( 3 ) J. J. Ritter and P. P. Minieri, ibid., 70, 4045 (1948),and Wieland and E . Dorrer, Ber.. 63,404 (1930).
II.
CFHj
I
1120
0
I1
111 _j. H(CII~CH),,--SIIC-R
The structure indicated for the telorner is supported by the identification of the amine CHa-CHCH2-CHXHz
I
CsHo
I
divided by weight of styrene) was obtained in 7 2 hours. The approximate molecular weight distribution of this product as determined by fractional distillation was: n = 1, 35y0; 71 = 2, l'i~o; and IZ > 2, 413%. These fractions were chiefly glycol acetates but contained simple styrene-acetic acid telomers as contaminants.
CsH6
Experimental
This formulation was substantiated by the preparation of the amine picrate which had a meltinq point identical with that reported for the picrate of 1,3-diphenylbutylamine. The telomerization of styrene with acetonitrile was conducted with sulfuric acid catalyst in either acetic acid or nitrobenzene. Nitrobenzene solvent was preferable to acetic acid, which competed as a telogen and led to small amounts of esters in addition to the desired amides. In some cases the telomers were isolated as the amides, but more frequently the crude product was hydrolyzed, and the resulting amines were isolated In a telomerization conducted in nitrobenzene solution a t 2.5' with 1 : 2 : 1 mole ratios of styrenp: acetonitrile: sulfuric acid, a 69% conversion was obtained in 24 hours. The hydrolyzed product comprised 21Y0 amine, n = 1 ; 18% amine, n = 2 ; and 61% amines, n > 2. Here, as with the teloineric ester, the fractions contained hydrocarbon contaminants. The n = 2 fraction contained approximately 2% hydrocarbon and 98% diphenylbutylamine. It was found that a lower ratio of acetonitrile to styrene increased the formation of the by-product styrene dimer. In an experiment similar to the one described above but having mole ratios of styrene: acetonitrile :sulfuric acid of 2 : 2 : 1, a 517, yield of total product was obtained in three hours. Of this, 11% was n = 1, 17% was n = 2, and 727, was n > 2. The n = 2 fraction from this experiment contained 15yohydrocarbon. Telomerization of Styrene with Formaldehyde in Acetic Acid.-In the Prins reaction, an olefin reacts with formaldehyde in the presence of an acid catalyst to form a 1,3-glyc01.~ By the telomerization of an olefin with formaldehyde, a,w-glycols have been prepared which contain a plurality of hydrocarbon units in the chain. The products have been isolated as the diacetates, which are believed to have the structure AcOCH*(CH&H).OAc
Telomerization of Styrene with Acetic Acid .-A solution of the catalyst, boron fluoride-acetic acid complex, was prepared by absorbing 500 g. of boron fluoride in 1 1. of acetic acid cooled in an ice-bath. The resulting solution was diluted with glacial acetic acid as required before reacting with styrene. The telomerization was brought about by adding 720 g. of styrene t o 4 1. of solution which was 0.5 M boron fluoride-acetic acid complex in acetic acid. After the homogeneous solution had been held at 25" for 20 hours, it was drowned in 25 I. of ice-cold sodium hydroxide. The resulting mixture was extracted with toluene, and the organic estract was washed with water and dried over calcium chloride. The toluene and unreacted styrene were removed by distillation under reduced pressure, and the telomers were fractionally distilled (Table 11). TABLE I1
DISTILLATION O F STTRENE-.4CBTIC ACID TELOMERS wt of fraction. g
No of fraction
86.3 12.3 52.3 54.0 67.8 55.1 33.0 10.4 26.0 86.7 47.4 174.0
1 2 3 4
5 6 7 8 0
10 11 R
-
n p .
oc
7.7 79-140 138-143 143 143-144 144-145 145 132-160 160-200 200-205 205-210
.....
Pressure, m m of inerciirv
?IZ1D
3
1 ,4920
1 1 1 1
1 0.2 0.2 0.3 0.3
1.5445 1,5480 1,5441 1.5419 1.5381 1.5378 1,5399 I ,5420 1,5622 1,5620
...
....
1
Total 681.9 Fraction 1 was a-phenylethyl acetate. Its boiling point and refractive index confirm its identification as cy- rather than 8-phenylethyl acetate (Table 111). The corresponding fraction from a similar experiment was characterized by elemental analysis and determination of its saponification equivalent. Anal. Calcd. for C10H1202: C, 73.14; 13, 7.37; sapn. equiv., 164. Found: C, 72.88; H, 7.52; sapn. equiv., 101. TARE 111 IDENTIFICATION OF TELOMERIC ACETATE,n
1
=
1
Refractive C6H5 n . p . , oc index when styrene is employed as the olefin. The prod- Fraction 1 7.7 (3 mm.) n Z 6 D 1 .4g::n uct containing two styrene units was presumed to e-Phenylethyl 72-7
