STUDIES IN TRIFLUOROMETHANESULPHONIC ACID-IV KINETICS AND MECHANISM OF ACYLATION OF AROMATIC COMPOUNDS

Article abstract of DOI:10.1016/S0040-4020(01)97639-2

A detailed kinetic study has been made of acylation reactions in solvent trifluoromethane sulphonic acid (CF3SO3H) using carboxylic acids as the electrophilic species involved.These species were shown to be probably the protonated form of the mixed anhydride.The reactions show high substrate selectivity characterised by high negative values of p⁺.Substituents in the carboxylic acids have a relatively small influence on the reactions rates due to a cancellation of substituents effects on the protonation of the mixed anhydride with those operating on the subsequent slow reaction of these species with the aromatic substrate.Anomalous effects were found for certain ortho substituents.The overall mechanism is discussed in terms of polar and steric effects in conjunction with the competing protonation of the aromatic bases, together with evidence from isotope effects.