Studies of Diarylalkanes. V. The Benzylation of Benzene and Chlorobenzene with Benzyl or p-Chlorobenzyl Chloride under the Influence of Various Catalysts

Abstract

Abstract The benzylation of benzene and chlorobenzene with benzyl or p-chlorobenzyl chloride under the influence of various catalysts has been carried out in order to elucidate the relation between the cleavage reaction of the DPM and the Friedel-Crafts benzylation. In the aluminum chloride- or gallium chloride-catalyzed benzylation, the compositions of the equilibrium mixture are similar to those of the cleavage reaction. It has been suggested that, in the presence of such catalysts, the DPM formed at an initial stage is cleft with the catalyst, and that the same equilibrium relationship as has been postulated in the cleavage reaction is established. On the other hand, in the aluminum chloride-, gallium chloride-nitro compound complex or in indium chloride, which does not exhibit the ability to cleave the DPM, both the products and the isomer distributions are different. It has been estiablished that the isomer distributions in the benzylation are affected by the reactivity of the reactive species as well as by the catalytic ability to cleave the DPM. It has also been found that, under the influence of a strong catalyst such as the aluminum chloride - nitromethane complex, the relative reactivity of p-chlorobenzyl chloride on benzene is equal to that of benzyl chloride, while the reactivity of the former is about half that of the latter in the presence of such a weak catalyst as indium chloride.