DEPENDENCE OF ISOTOPE EFFECTS ON CONFORMATION IN DECARBOXYLATION OF 3-CARBOXYBENZISOXAZOLES

Conformational analysis of 3-carboxybenzisoxazole and its 4-hydroxy-su bstituted derivative was performed by a semiempirical molecular dynami cs approach. The most stable conformers of the reactants and transitio n states from these simulations were used in calculations of the kinet ic isotope effects of carbon, nitrogen, oxygen and deuterium. It was s hown that the conformation of either reactant or transition state can significantly affect the magnitude of an isotope effect, especially fo r atoms involved in hydrogen bonding.