Jan. 5, 1955
81
%VINYL-1,3-BUTADIENE [CONTRIBUTION FROM THE BAKERLABORATORY OF CHEMISTRY AT CORNELL UNIVERSITY]
Z-Vinyl-l,3-butadiene BY A. T. BLOMQUIST AND JOSEPH A. VERDOL RECEIWDJUNE 16, 1954 Pyrolysis of 3-methylene-l,5-pentanediol diacetate may be controlled to afford either 2-vinyl-1.3-butadiene or .%(,&acetoxyethyl)-1,4-butadiene. The structures of the two substituted butadienes were confirmed by standard chemical and physical methods including those of infrared and ultraviolet spectrophotometry. The triene dimerizes and/or polymerizes with great ease even a t -5’.
Recent studies in this Laboratory have shown that the unsaturated acetates obtained by the thermal condensation of olefins with formaldehyde in an acetic acid-acetic anhydride medium are convenient intermediates for the preparation of certain substituted 1,3-b~tadienes.~Those derived from isobutylene-type olefins are of particular interest as they afford 2-substituted-1,3-butadienes smoothly upon pyrolysis. CHF~!-CHZCHZOAC
A ----f
1
L--
2
3
5
CHe=C-CH=CH2
I
,
---L
4
Fig. 1.-Infrared
,
,
,
,
,
I
6 7 8 9 10 11 12 1314 Wave length, p. spectrum of 2-vinyl-l,3-butadiene.
R R In this connection, 3-methylene-1,5-pentanediol Catalytic reduction of I11 required 96.5% of diacetate (I), a product of the thermal condensa- three molar equivalents of hydrogen and gave 3tion of isobutylene with formaldehyde,2aappeared methylpentane (IV), characterized by its physical to be worthy of study as i t should yield two buta- properties including its infrared spectrum. Mild diene derivatives by varying the pyrolysis con- oxidative ozonolysis converted I11 to mesoxalic ditions ; 2- (P-acetoxyethyl)- 1,3-butadiene (11) and acid (V), characterized as its phenylhydrazone. the cross-conjugated triene 2-vinyl-l,3-butadiene Addition of I11 to a benzene solution of maleic anhydride gave a crystalline adduct VI, m.p. 238(111). 239’, in Sly0 yield. Analysis of the latter indiA CHZ=C-CH~CH~OAC + cated that it comprised one mole of I11 and two I moles of maleic anhydride. The carbon skeleton CH~CHZOAC of the adduct was indicated by aromatization and 1 decarboxylation of its tetramethyl ester VI1 to A naphthalene. The above transformations are ilCH~=C-CH=CHZ ----f CHz=C-CH=CHz lustrated in the diagram below. I I CHZCHZOAC I1
CH=CHz I11
Pyrolysis of I a t 485’ in a nitrogen atmosphere over carborundum chips gave either I1 or I11 predominately depending upon the velocity of I through the furnace (see Experimental part). Pure 111, obtained after several redistillations, was a colorless volatile liquid, b.p. 44-45’, %*OD 1.4484, extremely prone to undergo dimerization and polymerization. Because of this all characterization studies were made using freshly distilled samples. The ultraviolet spectrum of I11 showed one principal absorption maximum, be%:’ 223 mp, log E 4.01, in accord with the 2-vinyl-1,3-butadiene structure. The infrared spectrum of I11 (Fig. I) also supported the cross-conjugated triene structure; strong maxima a t 6.12, 10.12, 10.97, 11.05 and 11.17 p (characteristic of RCH=CH2 and R2C=CH2) and a strong maximum a t 6.25 (characteristic of >C= c-c =cC=C-C=C
