Solvent effect in photolysis of chloro substituted benzyl chlorides

The effect of solvent on photolyses of 3-chloro and 4-chloro substituted be nzyl chlorides is described. Analysis of the products formed indicates that both radical and ionic intermediates are involved. In the first step, homo lytic benzylic C-Cl bond cleavage occurs, resulting in a radical pair. Furt her reaction pathway, however, depends upon the solvent used. In cyclohexan e and tetrahydrofuran, the products obtained are formed via an intermediate benzylic radical. Photolysis in acetonitrile, on the other hand, results i n products, which can be interpreted through intermediate formation of both benzylic cation and benzylic radical. The presence of LiAlH4 accelerates t he reduction of the C-Cl bond in the aromatic ring, leading to toluene as t he main product.