Theoretical investigation of sulfur and halogen-substituted carbocations

The stabilization of sulfur, fluorine and chlorine substituted carbocations was studied using hydride exchange reactions at the G2 level of theory; evaluation of the π bonding in these was performed using variation of the dihedral angle in the case of sulfur compounds and NRT and other bond order calculations for all compounds. Resonance contributors were estimated using the NRT method. Sulfur substitution stabilizes carbocations comparable to oxygen substitution covered previously. The stability of trisubstituted carbocations is enhanced over the oxygen analogues. Halogen substitution leads to destabilization, which is more extreme for the fluorine-substituted carbocations.