The Thermal Isobutylene-Formaldehyde Condensation1 I I

dimedon derivative) in 73% yield. ... steel bomb, the mixture was heated with shaking for 8 hours ... a very weak test for the hydroxyl group with cer...
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Vol. 77



The Thermal Isobutylene-Formaldehyde Condensation1 BY A. T. BLOMQUIST AND



RECEIVED JUSE 16, 1954 Uncatalyzed thermal condensation of isobutylene with paraformaldehyde in acrtic acid-acetic anhydride affords principally 3-methyl-3-butene-1-01 acetate and 3-methylene-] ,S-pentanediol diacetate. The latter is the principal product of :I similar condensation of 3-methyl-3-butene-1-01 acetate with paraformaldehyde. The structure of these products was established by standard chemical and physical methods. Accessory products of the condensations which were isolated and characterized included methanol, methyl acetate and isoprene glvcol diacetate. Isoprene was obtained on pyrolysis of 3-methyl-3-butene-1-01 acetate.

Recent studies of the uncatalyzed thermal condensation of olefins with formaldehyde by B a i q 2 -4rnold3 and workers in this Laboratory4 have shown that the principal products of the reaction are unsaturated primary alcohols. Further, the carbon-carbon double bond in these alcohols has been found to occupy a position adjacent to its original location in the olefins. RCHzCH=CHz









CH3 11 I C H P = C ( C H ~ C H ~ O H ) ~ CHZ=C( CH2CH20Ac) I11 V CHI











One of several possible satisfactory explanations for this shift of the unsaturation was advanced by Price4" and by Arnold3 who suggested the intermediate formation of a "transient cyclic complex" as indicated below.

Those not characterized were obtained in small amounts and included high boiling substances which presumably comprised polyhydric alcohols and their acetates resulting from formaldehyde condensations with I , 11,111, I V and V. I n a second similar thermal olefin-formaldehyde / / E 2 )'H3 condensation using pure I1 as the olefinic reactant CH CH? --+ CH \CH? the unsaturated diacetate V, containing some 111 It I R-JH5 (0I1 and IV, was obtained in 50-6070 yield. The secR-CH OH ondary products observed here were small amounts \H.' of V I and high boiling polyhydric alcohols and their The foregoing has prompted a study of the be- acetates. havior of isobutylene in its thermal condensation Pure I and I1 were difficult to obtain by fracwith formaldehyde as the expected products would tional distillation of the isobutylene-formaldehyde be useful intermediates for the synthesis of a num- reaction mixture, Acetylation of those fractions ber of interesting simple organic compounds for comprising I , I1 and their mixtures using acetic anpolymerization reactions of the addition and con- hydride and pyridine gave the pure acetate 11, b.p. densation type. 143-144', e z o 1.4201. ~ Its infrared spectrum Our experience with the thermal olefin-formal- showed strong absorption a t 6.05 and 11.25 (for dehyde reaction had indicated that the desired >C=CHz) and also a t 5.75 p , characteristic of an products, predominately as acetates, were usually ester group.5 obtained in higher yields in a reaction medium of The acetate I1 decolorized solutions of potassiuni acetic acid-acetic anhydride. Accordingly, such a permanganate in water and bromine in carbon tctinediuni was used in the present study. rachloride. Catalytic reduction of I1 required The principal products obtained upon heating 1.05 molar equivalents of hydrogen giving a prodparaformaldehyde with an excess of isobutylene in uct indistinguishable from isoamyl acetate. Reacetic acid-acetic anhydride for 8 hours at 190" ductive ozonolysis of I1 gave fornialdehyde (as its were 3-methyl-3-buten-1-01 and its acetate, I and dimedon derivative) in 73% yield. Pyrolysis of I1 I1 (50-60y0) and 3-methylene-l,5pentanedioland a t 550' over carborundum resulted in a 737p conits acetates, 111,I V and V (13%). version to isoprene in one pass. The isoprene obA number of accessory products were also formed. tained was characterized by its physical properties, Those isolated and characterized were methanol, 5600 methyl acetate and isoprene glycol diacetate, VI. I1 A CH*=C-CH=CHz ( 1 ) T h e work reported here mas done as p a r t of a research program a t t h e Baker Laboratory of Chemistry, Cornell University, sponsored hy T h e B. F. Goodrich Company. (2) J. P. Bain, TAISJOURNAL, 68, 638 (194G). (3) R . T.Arnold a n d J. F. Dowdall, ibid., 7 0 , 2690 (1848); R. T . Arnold, R. W. Amidon and R. M . Dodson, i b i d . , 74, 2871 (1950). (4) A. T. Blomquist, L. I. Diuguid, M. Passer a n d C. S. Schollenherger, unpublished; M. Passer, Thesis, Cornell University, 1948; C. S. Schollenberger, Thesis, Cornell University, 1947. (4) (a) C. C. Price, "Reactions a t Carbon-Carbon DoulJle Bonds," Interscience Publishers, Tnc., New York, N. Y.,1946, p. 46.



including its infrared spectrum, and by its DielsAlder adduct with maleic anhydride. Hydrolysis or methanolysis of I1 gave the pure unsaturated alcohol I , b.p. 131-132', e Z 1.4340. o~ The pure unsaturated diacetate V was obtained (i I!.)Gilman, "Organic Chrnlistry," \'