Superelectrophilic Gallium(III) Homodimers in Gallium Chloride-Mediated Methylation of Benzene: A Theoretical Study

Abstract

The GaCl3-mediated Friedel–Crafts alkylation of benzene by methyl chloride has been studied by means of density functional theory computations at the M062X/6-311+G(2d,2p) level of theory. The role of superelectrophilic Ga2Cl6 homodimers has been confirmed and explained. The results are consistent with the observation of second-order rate dependence in GaCl3-mediated Friedel–Crafts alkylations. This work also reveals that, even in a typical Friedel–Crafts alkylation, no Wheland-type σ-complex can be modeled, suggesting a concerted electrophilic aromatic substitution. Also refuted is the possibility of activation of the arene nucleophile by the Lewis acid.