Theoretical and Physical Aspects of Stepwise Mechanisms in Acyl-Transfer Reactions

Recent applications of theoretical and physical approaches to the elucidation of acyl-transfer mechanisms have led to further clarifications of structures of intermediates and transition states involved in the stepwise reaction paths. Gas-phase acyl-transfer reactions, both experimental and theoretical, are surveyed, in which factors conductive to the stepwise path are discussed. Aminolysis reactions of carbonyl and thiocarbonyl esters in solution are reviewed with special emphasis of transition state variation with substituents in the nucleophile, acyl and leaving groups applying Marcus theory, Bell-Evans-Palanyi principle, principle of microscopic reversibility, DFTFukui function, reactivity-selectivity principle, natural bond orbital analysis and More O'Ferrall-Jencks diagram etc. The use of cross-interaction constants as a mechanistic tool is stressed.