Differences in the electronic structure of sulfenyl chlorides and bromides as possible reasons for their different reactivities toward aromatic compounds

Abstract

The electronic structure of C- and N-sulfenyl chlorides and bromides was studied by semiempirical quantum-chemical methods. The sulfur atom in sulfenyl chlorides always possesses a larger positive charge than the sulfur atom in the corresponding sulfenyl bromides, which is responsible for the higher electrophilicity of sulfenyl chlorides as sulfenylating agents in charge-controlled reactions. Electrophilic properties of sulfenyl bromides stem to a considerable extent from the low-lying lowest unoccupied molecular orbital. The contribution of bromine to the LUMO can exceed that of the sulfur atom, thus favoring formation of the bromination products in orbital-controlled reactions.