SOLVENT EFFECTS IN PHOTOLYSIS OF CHLORO SUBSTITUTED BENZYL CHLORIDES
Berta Košmrlj and Boris Šket*
Faculty of Chemistry and Chemical Technology, University of Ljubljana, Aškerèeva 5, 1000 Ljubljana, Slovenia
The effect of solvent on photolyses of 3-chloro and 4-chloro substituted benzyl chlorides is described. Analysis of the products formed indicates that both radical and ionic intermediates are involved. In the first step, homolytic benzylic C-Cl bond cleavage occurs, resulting in a radical pair. Further reaction pathway, however, depends upon the solvent used. In cyclohexane and tetrahydrofuran, the products obtained are formed via an intermediate benzylic radical. Photolysis in acetonitrile, on the other hand, results in products, which can be interpreted through intermediate formation of both benzylic cation and benzylic radical. The presence of LiAlH4 accelerates the reduction of the C-Cl bond in the aromatic ring, leading to toluene as the main product.