THEORETICAL AND EXPERIMENTAL-STUDY ON THE REACTION-MECHANISM OF PHOTOLYSIS AND SOLVOLYSIS OF ARYLVINYL HALIDES

The reaction mechanisms of solvolysis and photolysis of arylvinyl halides have been studied in terms of ab initio molecular orbital calculations and experiments. The frontier orbital of the p-methoxyphenylvinyl cation requires that nucleophiles attack not only the vinylic carbon but also the ipso position of the p-methoxy group. The experimental results also show the possibility of a mechanism proceeding via the ipso intermediate. The solvolysis affords exclusively the vinyl type products because of the instability of the ipso intermediate. On the other hand, some of the ipso intermediate does not decompose to produce the vinyl cation under the mild conditions of photolysis. Substitution of the p-methoxy group in the anisyl fragment occurs in cases where the nucleophile has the ability to form a bond comparable with or stronger than the original C-O bond.