An ab initio study concerning the experimental observability of C3H62+ isomers

The thermochemistry and structure of the three lowest energy C3H62+ dications, namely the dimethylcarbene, trimethylene and propene dications, have been studied with ab initio molecular orbital calculations up to the G2(ZPE=MP2) level. The geometries of the three dications are significantly influenced by hyperconjugation. Both the dimethylcarbene and trimethylene dications are predicted to be stable species and should be observable under appropriate experimental conditions. However, the propene dication is predicted to reside at best in an extremely shallow potential energy well and is unlikely to be experimentally observable. The predicted heats of formation (ΔfH°298 in kJ mol−1) are 2491, 2499 and 2539 for the dimethylcarbene, trimethylene and propene dications, respectively.