ACID-CATALYZED REACTIONS OF VINYL COMPOUNDS: IV. MECHANISM OF FORMATION OF THE PRODUCTS OF THE REACTION OF VINYL ACETATE AND BENZENE

Abstract

In part II of this series the isolation and identification of nine products from the reaction of vinyl acetate with benzene and aluminium chloride were described. This paper presents a discussion of the mechanism of formation of these compounds.A comparison of the aluminium chloride catalyzed reactions of benzene with vinyl acetate and ethyl acetate is described. The reaction with ethyl acetate gave all the monocyclic products obtained from the reaction involving vinyl acetate, as well as m-diethylbenzene. The ratio of the ortho and para isomers of ethylacetophenone is the same in both reactions, which suggests that the same acetylating species is involved. The fact that none of the three polycyclic products is obtained from the reaction involving ethyl acetate suggests that the vinyl moiety of the ester is involved in the formation of these compounds from vinyl acetate. The use of 14C-labelled vinyl acetate confirmed the fact that the synthesis of 9,10-dimethylanthracene involved only the vinyl part of the ester.A study of the reactions of ethyl acetate and vinyl acetate with aluminium chloride showed that ethyl chloride and vinyl chloride, respectively, may be intermediates in the alkylation of benzene with these reagents. Evidence is presented that 1-phenylethyl chloride may also be an intermediate product in the reaction of vinyl acetate and benzene. 1,1-Diphenylethane is believed to be involved in the formation of 9,10-dimethylanthracene, the final step of which is thought to occur by the dehydrogenation of 9,10-dihydro-9,10-dimethylanthracene.