Comments on chemical properties reported for diphenyl disulfide and its derivatives: The merit of the phenyl groups

The symmetrical 2,2′-disubstitued derivatives of diphenyl disulfide showing widely spanning rates of electrophilic attack of the HIV-1 nucleocapsid protein p7 zinc fingers have been rationalized, based on the lowest unoccupied molecular orbital (LUMO)-lowering approach, by the substituents' π-effects and the hydrogen bond stabilization effects. In the 2,2′-amide- and 4,4′-N-amide-substituted derivatives, the extent of LUMO lowering has been reduced by the destabilization of lone-pair bond orbital, lp(N), present on the nitrogen atom of N-amide. From the natural bond orbital viewpoint, hydrogen bond stabilization of LUMO is mainly governed by stabilization of the σ*_SS bond orbital.