Localized charge distributions in stable n-hexane radical cations

The potential energy surface of n-hexane radical cations is probed theoretically. The structures with low internal energies are characterized by extensive lengthening of one of the three innermost C-C bonds. This C-C bond stretch is induced by localization of the positive charge. For an elongated terminal C-C bond we calculated an energy which is 0.4 eV higher than that for a stretched central C-C bond. The n-hexane geometries with several C-C bonds stretched do not represent stationary points on the potential energy surface. Comparison with previous dissociative-neutralization experiments of low-internal-energy n-hexane ions shows that the fragmentation pathways reflect the two lowest energy structures.