Mechanism of Aromatic Hydrocarbon Acylation by Substituted Benzoic Acids: A Novel Reaction Pathway

Abstract

Aromatic hydrocarbons are susceptible to direct acylation by benzoic acids with high yields bearing ortho or para alkyl groups as substituents under Friedel–Crafts reaction conditions. The α-H of the alkyl moiety seems to be responsible for the observed relatively high reaction rates of conversion. Carbanion-like species are proposed as reaction intermediates, which also operate as strong bases in the reaction rate-determining steps. Trapping experiments, deuterium isotopic effects, and kinetics data favor a concerted reaction pathway where proton transfer from the hydrocarbon molecule to a carbanionic intermediate takes place with a simultaneous electrophilic attack of the carbonylic carbon atom.