AN MCSCF AB INITIO STUDY OF C-CL BOND CLEAVAGE IN H3C-Cl

The thermal, photochemical and reductive dehalogenations of methyl chloride (H3C-Cl) are studied with the ab initio MCSCFmethod using three different basis sets (3-2 lG*, 6-31G* and 6-31 +G*). It has been found that both thermal and photochemicaldecomposition produce a methyl and a chlorine radical. The photochemical decomposition involves excitation of the H3C-Clmolecule from the singlet ground state to a singlet or triplet n-u* state which dissociates directly to these products. The reductivedehalogenation involves the formation of a metastable anion (resulting from electron transfer to the chloromethane) which dissociatesimmediately to a methyl radical and chloride anion. While for the thermal and photochemical decomposition the resultsobtained at the various computational levels do not significantly differ, for a reliable description of the reductive dehalogenation,it is essential to use a basis set, such as 6-31 +G*, which includes appropriate sp-type diffuse functions