PYROLYTIC DECOMPOSITION OF ALLYLIC ESTERS

Abstract

The acetate of 6,6-dimethyl-2-cyclohexen-l-ol was thermally decomposed and the pyrolysis products were characterized. This allylic ester decomposed with difficulty. Under conditions which led to complete decomposition of 3-acctoxycyclohexene, 6,6-dimethyl-2-cyclohexen-l-ol acetate was virtually unreacted. Complote decomposition of the allylic acetate was achieved at about 600oC. The pyrolysis products consisted mainly of o-xylene, toluene, 5,5-dimethyl-1,3-cyclohexadiene and acetic acid. The aromatic compounds are thought to be formed from the less stable dione. Partial decomposition of ester enriched with deuterium in the 4-position, permitted estimation of the isotope effect, kH/kD, for the pyrolytic elimination. Tne value obtained was about 2. Together with other experimental evidence, it indicates that the main mode of decomposition is 1,4-conjugate elimination and that allylic rearrangement, if it occurs at all, is unimportant.