| Abstract: | The potential energy surface for the CH5N]+˙ system has been investigated using ab initio molecular orbital calculations with large, polarization basis sets and incorporating valence-electron correlation. Two CH5N]+˙ isomers can be distinguished: the well known methylamine radical cation, CH3NH2]+˙, and the less familiar methylenammonium radical cation, CH2NH3]+˙. The latter is calculated to lie 8 kJ mol?1 lower in energy. A substantial barrier (176 kJ mol?1) is predicted for rearrangement of CH2NH3]+˙ to CH3NH2]+˙. In addition, a large barrier (202 kJ mol?1) is found for loss of a hydrogen radical from CH2NH3]+˙ via direct N—H bond cleavage to give the aminomethyl cation CH2NH2]+. These results are consistent with the existence of the methylenammonium ion CH2NH3]+˙ as a stable observable species. The barrier to loss of a hydrogen radical from CH3NH2]+˙ is calculated to be 140 kJ mol?1. |
