RESEARCH DEPARTMENT, MONSANTO CHEMICAL COMPANY ]
[CONTRIBUTION FROM THE CENTRAL
T H E REACTION OF STYRENE WITH ALDEHYDES WILLIAM S. EMERSON
Received June 16, 1946
Prins (1, 2) originally condensed styrene with formaldehyde by means of sulfuric acid in glacial acetic acid to give principally phenyltrimethylene glycol diacetate as well as some phenyl-1 ,3-dioxane. He erroneously formulated these compounds as derivatives of 2-phenyltrimethylene glycol. Later Fourneau, Benoit, and Firniinich (3,4) showed these to be derived from l-phenyltrimethylene glycol. They hydrolyzed the diacetate to the glycol, as Prins had, and then prepared its dibenzoate, which proved to be identical with that which Rupe and Muller ( 5 ) had obtained by reducing sodium hydroxymethyleneacetophenone. These latter investigators demonstrated the identity of their dibenzoate by pyrolyzing it to cinnamyl benzoate. Under the same conditions employed by Prins (1) we have caused styrene to react with acetaldehyde, propionaldehyde, n-butyraldehyde, and isobutyraldehyde. The initial condensation products decomposed partially to give off acetic acid on the first attempt a t fractionation. However, after the acetic acid had been washed out of this distillate with \Tater, the water-insoluble material was easily separated by fractional distillation into recovered styrene, a diene (I), a dioxane (JI), a glycol acetate (IV), and a high-boiling oil. The dienes obtained from the reactions with acetaldehyde and propionaldehyde were identified as l-phenylbutadiene and l-phenyl-1 ,3-pentadiene, respectively, by treating them with maleic anhydride to obtain known Diels-Alder adducts (111). The diene from the n-butyraldehyde reaction also added maleic anhydride. By analogy this adduct has been formulated as 3-phenyl-ðylA4-tetrrthydrophthalic anhydride. The diene from the isobutyraldehyde reaction would not add maleic anhydride either when the ingredients were heated together over an open flame or when they were allowed to stand for two weeks in benzene solution. No dioxane was obtained from the reaction between styrene and n-butyraldehyde. The dioxanes from the other three reactions were pyrolyzed a t 425-575" to the corresponding dienes in 30-43Lr, conversion by passing their vapors, together with steam, over a phosphoric acid catalyst supported on silica gel. Because of this reaction and since they were synthesized from the corresponding glycol esters, these compounds have been formulated as 2,6-dialkyl-4-phenyl1,3-dioxanes. The reaction between styrene and acetaldehyde yielded largely l-phenyl-1 ,3butylene glycol diacetate contaminated with some monoacetate which could not be separated by fractional distillation. The esters from the other condensations were all monoacetates of the corresponding glycols. These esters all gave dienes in 5445% conversion when their vapors, together with steam, were passed a t 496-575" over a phosphoric acid catalyst supported on silica gel. These converBions are slightly better than the 53% of butadiene recently obtained by the 464
465
REACTION OF STYRENE WITH ALDEHYDES
pyrolysis of 1,3-butylene glycol diacetate (6). Treatment of the acetates with ten per cent aqueous potassium hydroxide produced the corresponding glycols (V) in 56-8170 yield. An attempted acetylation of the l-phenyl-l,3-hexylene
/-\
CHCHzCHR
W l
-
I
0-CH-0
I
/
~H=CHCH=CRR’ \A
R’
I
I1
c=o
O=C
\
‘0’ I11
/
-
//
-1
~HCH~CHOHCHRR’ OCOCHa IV
CH
/ \
/-\
\=)-CH
I
0
\ / C H/ \
\~HOH 2 CH~CHOHCHRR’ v /-\ 1/-\-CH
\==/I
CHR’
I
0
R’
VI
CHCH,
H
CH
/ \0 I RCH CHR‘ \ / 0
VI1
CHaCH
\ /
CHCHS
0
VI11
glycol yielded only a monoacetate. Moreover the monoacetate of l-phenyl-4methyl-l,3-amylene glycol did not react with acetic anhydride. Since these glycols did not prove amenable to solid derivative formation, they were treated with the original aldehyde, calcium chloride, and a few drops of hydrochloric acid to give the same dioxane which was isolated from the original condensation reaction in conversions of 17-80%, l-Phenyl-l,3-hexylene glycol would not
TABLE I CONDENSATION REACTIONS % CONVEB-
CONVEB% STYBENE % CONVER- %SION TO
ALDEHYDE USED
SION TO GLYCOL
-
DIOXANE
YON0 OR
szi-o
% 'ONVER* BOILINC
DEESTEB
138 g. 180 g. 225 g. 225 g .
Paraldehyde.. . , . . . . . . . . . . . . , . . , , Propionaldehyde.. . . . . . . . . . . . . . . , n-Butyraldehyde . . . , . . . . . . . . . . . . Isobutyraldehyde.. . . . . . . . . . . . . . .
5 18 23 14
1
0 13
14
23
j
39 13
16
17
TABLE I1 COMPOUNDS PREPARED
H
H
CH3 CHzCHa CHI
H H CHa
H CHs CHzCH3
H H H
CHa CH2CHa CH(CHa)z
1
89-94 /14 mm .b 98-125/1 Id 127-130/ 1l e 126130/11f
1.6010' 1.5952d 1.59176 1.5985 0.926 91.2 8.86 90.59.06
115-116g 156-157h 152-153
:ibiCa CH(CHs)z
1
~
175.0 6.25 75.26.44
125-130/14 150-155 14 159-162/11
l-Phenyl-l,3-butylene Glycol Monoacetates, Type Formula IV -~ H 162-164/14j 1.4883 1.075 69.3 7.69 H H 169-171/14 1.4902 1.057 70.3 8.11 CHs 1.4867 1.038 71.2 8.47 H 179-181/11 CHzCH3 1.4941 1.045 71.2 8.47 CH3 175-176/11 CHP ~
68.57.35 70.58.06 71.08.33 72.08.27
l-Phenyl-l,3-butylene Glycols, Type Formula V H CHa CHGHa CH3
H H
H CH3
173-174/13k 180-183/16 170-172111 181-183/14
1.5319 1.073 72.3 8.44 73.18.45 1.5241 1.051 73.4 8.89 74.18.84 1.4955 1.020 74.3 9.28 74.39.14 1.5133 1.035 74.3 9.281 74.78.75
Dioxanes from Styrene Dimer, Type Formulas VI and VI1 ~
CHa' CHzCHs (CH*)*CHV CH(CHs)z
CHI' CHzCHs (CH2)zCHs CH (CHa)z
203-213/11 220-235,14 222-232/11 222-229/11
1.5762 1.035 86.4 7.91 86.37.87 1.5451 1.038 81.5 8.65 81.78.57 1.5505 1.019 81.9 9.09 84.08.63 1.5478 1.024 81.9 9.09 82.58.71 466
REACTION OF STYRENE WITH ALDEHYDES
467
TABLE 11-Concluded 0,411 the analyses are microanalyses performed by the Arlington Laboratories, Fairfax, Virginia. b Klages, (8) gives b.p. 86"/11 mm. and (9) b.p. 90"/15. c Klages (9) gives n t 1.6128 and Cotton and Mouton (10) give n'v 1.6089. d K 1 a g e ~ ,(9) gives b.p. 116"/16 mm. and n'," 1.6111. e Klages, (9) gives b.p. 128"/16 mm. and n'," 1.6025. f Perkin, (11) gives b.p. 248-250". 0 Diels and Alder, (12) give m.p. 120'. h Diels and Alder, (12) give m.p. 158-159'. i T h i s is probably largely the diacetate for which Franke and Kohn (13) give b.p. 157"/10 mm. Calc'd: C, 67.2; H, 7.20. An extremely viscous syrup. Franke and Kohn, (13) describe i t as a powder which sinters at 60" and melts roughly at 73.5", b.p. 162-164"/11 mm. Sprague and Adkins, (14) give its b.p. as 175-178'/21 mm. More probable structure: Formula VIII.
form a dioxane under these conditions. This was not surprising since the corresponding dioxane could not be isolated from the original condensation. No attempt was made to prove the structures of the high-boiling by-products. The carbon-hydrogen analyses of three of them suggested that they might be dioxanes derived from styrene dimer and the aldehyde in question (VI)and (VII). The product obtained from styrene and acetaldehyde had a higher carbon and lower hydrogen content than this structure would require. Therefore, it may be a dihydropyran (VIII) derived from styrene dimer by the same mechanism as that recently postulated by Raker (6) in the reaction between propylene and formaldehyde. The likely assumption must also be made that a molecule of acetic acid was lost on distillation. EXPERIMENTAL
Condensations. These were run according to the method of Prins (1) with but slight modification. I n a 2-1. three-necked flask equipped with a thermometer, stirrer, and dropping-funnel was placed 660 g. of glacial acetic acid and 96 g. of concentrated sulfuric acid. When this mixture had been cooled t o 20' with a cold water-bath, 10 g. of the aldehyde in question was added. Then, while the temperature of the reaction was held at 15-20', the remainder of the aldehyde mixed with 312 g. of styrene was gradually added over a one- t o two-hour period. The stirring and cooling were continued for fifteen and one-half t o seventeen hours longer. After dilution with 2 1. of water, the reaction mixtures were extracted three times with benzene. These extracts were washed twice with excess aqueous sodium bicarbonate and then distilled with considerable decomposition until no further volatile material could be collected. The distillate was washed twice with water and then carefully fractionated t o separate the products. These reactions are summarized in Table I. Compounds prepared. All compounds prepared, together with their physical properties and analyses, are summarized in Table 11. The conversions shown in Table I are based on the structures shown, and are calculated from styrene. As indicated, fractionation of each once-distilled reaction mixture yielded unreacted styrene, a phenylalkadiene, a 2,6-dialkyl4-phenyl-lf3-dioxane, a 1-phenyl-I, 3-alkylene glycol mono- or di-acetate, and a highboiling oil which was possibly a mixture of dioxanes derived from styrene dimer. Pyrolyses. The dienes were also obtained by pyrolyzing the appropriate ester or dioxane in the apparatus described previously ( 7 ) . These pyrolyses mere conducted at pressures
468
WILLIAM S. EMERSON
of 85-95 mm. in the presence of steam and a phosphoric acid catalyst supported on silica
gel. They are summarized in Table 111. TABLE I11
PYROLYSES "Em.,"C.
CHARGE
;z
50 g. l-Phenyl-1,3-butylene 496-510 25 glycol diacetate 77 g. l-Phenyl-1,3-amylene 550-575 55 glycol monoacetate 174 g. 1-Phenyl-1,a-hexylene 550-575 120 glycol monoacetate 60 g. l-Phenyl-4-methyl-l,3550-575 40 amylene glycol monoacetate 50 g. 2,6-Dimethyl-4-phenyl- 425-440 40 1,3-dioxane 30 g. 2,6-Diethyl-4-phenyl550-575 25 1,3-dioxane 83 g. 2,6-Diisopropyl-4-phenyl 550-575 50 1,a-dioxane
-
-
%CON'EBSIO?
% RE-
1-Phenylbutadiene
62
-
1-Phenyl-l13-pentadiene
64
13
1-Phenyl-l ,3-hexadiene
54
20
1-Phenyl-4-methyl-1,3pentadiene
65
12
1-Phenylbutadiene
30
24
l-Phenyl-l,3-pentadiene
33
30
l-Phenyl-4-methyl-l,3pentadiene
43
39
PRODUCT
:OVEBY
-
-
-
TABLE I V HYDROLYSES ESTER USED
GLYCOL OBTAINED
1-Phenyl-l ,3-butylene glycol diacetate. . . . . . .
l-Phenyl-l,3-amylene glycol monoacetate . . . l-Phenyl-1,3-hexylene glycol monoacetate. . . l-Phenyl-4-methyl-l,3-amylene glycol monoacetate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1%
l-Phenyl-l,3-butylene 1-Phenyl-l ,3-amylene 1-Phenyl-1,3-hexylene
YIJ%tD
56 62 70
1
l-Phenyl-4-methyl-l,3-amylene 81
TABLE V DIOXANEPREPARATIONS
--
I-
l-Phenyl-l,3-butyIene. . . Paraldehyde SO l-Phenyl-l,3-amylene. . . Propionaldehyde 69 1-Phenyl-4-methyl 1,3amylene. . . . . . . . , . , . . . . Isobutyraldehyde 17
128-133/15 mm. 146-150/11 mm.
1.5084 1.5005
1.5070 1.5006
162-166/15 mm.
1.4959
1.4923
d-PhenylS-alkyl-b4-tetrahydrophthaZicanhydrides were prepared by heating for a few minutes at the boiling point a mixture of the appropriate diene and an equimolar quantity of maleic anhydride. Upon cooling, the compounds were crystallized from benzene. Their properties are shown in Table 11. 1-Phenyl-1 ,S-allcylene glycols were prepared by refluxing for five hours the corresponding l-phenyl-1,3-alkylene glycol mono- or di-acetate with a two-fold quantity of ten per cent
REACTION OF STYRENE WITH ALDEHYDES
469
aqueous potassium hydroxide. The cooled mixtures were extracted three times with benzene. Distillation of these extracts yielded the glycols, whose properties are summarized in Table 11. The yields obtained are shown in Table IV. 1-Phenyl-1 ,d-hexylene glycol monoacetate. A mixture of 39 g. of l-phenyl-l,3-hexylene glycol, 19.5 g. of fused sodium acetate, and 195 cc. of acetic anhydride was boiled under reflux for two hours, cooled, and poured into 1liter of water. After the excess of acetic anhydride had decomposed, the product was removed by three benzene extractions. Distillation of these benzene extracts yielded 36 g. (76%) of l-phenyl-l ,3-hesylene glycol monoacetate, b.p. 169-181°/12mm., n: 1.4905-1.4859. The pure monoacetate had sh0n.n n: 1.4867. Attempted acetylation of 1 -phenyl-.&methyl-l,3-amylene glycol monoacelate. A mixture of 14 g . of l-phenyl-4-methyl-l,3-amylene glycol monoacetate, 7 g. of fused sodium acetate, and 70 cc. of acetic anhydride was heated under reflux for two hours and then worked up as in the previous experiment. There was recovered on distillation 8.5 g. (61%) of l-phenyl4-methyl-] ,3-amylene glycol monoacetate, b.p. 174-177"/11 mm., n: 1.4939. The pure compound had boiled a t 175-176°/11 mm., n: 1.4941. 2,6-Dialkyl-,$-phenyl-l,%dioxanes. T o equimolar quantities of the l-phenyl-l,3-alkylene glycol and the corresponding aldehyde was added one per cent of concentrated hydrc chloric acid and ten per cent of anhydrous calcium chloride. After standing three days, the mixture was diluted with benzene, decanted from the calcium chloride and washed with aqueous sodium bicarbonate. Distillation yielded the desired dioxane. The reaction mixture from the l-phenyl-4-methyl-l,3-amylene glycol and isobutyraldehyde, after standing three days, was treated with an additional one per cent of concentrated hydrochloric acid, heated on the steam-bath for two hours, and then allowed to stand two days more before distillation. Even this treatment failed t o produce any dioxane from l-phenyl-l ,3hexylene glycol and n-butyraldehyde. These preparations are summarized in Table T. SUMMARY
Styrene has been condensed with acetaldehyde, propionaldehyde, n-butyraldehyde, and isobutyraldehyde by means of sulfuric acid in glacial acetic acid. The products isolated were the corresponding l-phenyl-l,3-alkadiene, 2,6dialkyl-$-phenyl-1,3-dioxane,l-phenyl-l,3-alkylene glycol mono- or di-acetate, and a high-boiling oil probably derived from styrene dimer. DAYTON7, OHIO
REFERENCES (1) PRINS,Chem. Weekblad, 16, 1510 (1919); Chem. Zentr., I, 423 (1920). (2) PRINS,Proc. Acad. Sei. Amsterdam, 22, 51 (1919); Chem. Abstr., 14, 1662 (1920). (3) FOURNEAU, BENOIT,AND FIRMINICH, Bull. SOC. chim., 47, 858 (1930). (4) FOURNEAU, BENOIT,AND FIRMINICH, Bull. soc. chim., 47, 894 (1930). (5) RUPEAND MULLER, Helv. Chim. Acta, 4, 841 (1921). (6) BAKER,J . Chem. Soc., 296 (1944). (7) EMERSON AND AGNEW,J . Am. Chem. Soc., 67, 518 (1945). (8) KLAGES,Ber., 37, 2301 (1904). (9) KLAGES, Ber., 40, 1768 (1907). (10) COTTON AND MOUTON, Ann. chim., [8] 28, 214 (1913). (11) PERKIN,J. Chem., Soc., 3G, 141 (1879). (12) DIELSAND ALDER,Ber., 62, 2081 (1929). (13) FRANXEAND KOHN,Monatsh., 27, 1115 (1906). (14) SPRAGUE AND ADKINS, J. Am. Chem. Soc., 66, 2669 (1934).
