Electronic Structure of Lone Pairs. II. Disulfides and Acyl Thiol

The electronic structure and the electronic transition of three cyclic disulfides, (CH2)3S2, (CH2)4S2, and (CH3)2S2, are calculated by the semi-empirical ASMO SCF method in order to study the interaction of the neighbouring lone pairs of the S–S bond in connection with the ability of reductive scission. It is concluded that the absorption at 2500–3000 Å is the transition of n–σ* and that the variation in the maximum for the various cyclic disulfides and the chain disulfide are induced by the change in the dihedral angle that a molecule can take. The electronic structure and the reactivity of (CH3)2S2, CH3SSH, and CH3SCOCH3 are then discussed on the basis of an extended Hückel calculation. It is suggested that there is the possibility of an interaction between two molecules, R2S2, through the S–S bond of each molecule, in the HO of one molecule and in the LV of another.