Homolytic mechanisms of aromatic rearrangements. Part I. The rearrangement of N-chloroacetanilide

Abstract

The kinetics and products of the rearrangement of N-chloroacetanilide, catalysed by light and by benzoyl peroxide in carbon tetrachloride, catalysed by t-butyl peroxide in chlorobenzene, and in hot glacial acetic acid, and the products of the rearrangement catalysed by hydrogen chloride in acetic acid and in carbon tetrachloride, have been investigated. The reactions in the presence of light or free-radical initiators, and in acetic acid, are autocatalysed, partly owing to the formation of hydrogen chloride in a side-reaction. The kinetics, and the ratios of isomeric chloroacetanilides formed under various conditions, are consistent with an initial homolytic reaction, which is followed by a faster, heterolytic reaction, catalysed by hydrogen chloride. In the presence of organic peroxides, a third mechanism, involving nuclear chlorination of acetanilide by t-butyl hypochlorite or benzoyl hypochlorite, is also an important contributor to the total reaction.