Complete active space self consistent field and externally contracted Cl potential energy curves for the CH3F– and CH3Cl– anions

Abstract

Ab initio calculations using the Complete Active Space SCF (CAS SCF) and externally Contracted Cl (CCl) methods and optimized basis sets have been performed to study the stability of the negatively charged molecular ions CH₃F^– and CH₃Cl^–. Neither of the molecules has a positive electron affinity. Both systems are essentially formed of the parent molecule with the extra electron in a very diffuse molecular orbital extending out from the methyl group. The extra electron moves over to the halogen atom when the RX bond is dissociated. The barrier for the dissociative electron attachment reaction of methyl fluoride and methyl chloride is calculated to be 230 and 130 kJ mol^–1, respectively. The solvent effect on the theoretical potential curves is discussed.