ChemInform Abstract: Theoretical Study on Carbocation with a Triple Bond

The vinyl cation with a ethynyl fragment, C4H3+ is investigated with ab initio molecular orbital calculations. Two geometrical isomers of C4H3+, open chain and triangular geometries are calculated in order to ascertain the existence of the triangular isomer. The 4–31G* and MP3/6–31G*//4–31G* level calculations confirm that the latter is more stable than the former. However, the activation energy for intra-conversion is considered to be rather small. The calculated results are analyzed by comparing with experimental results. The relation between molecular vibration and reaction is analyzed by dynamic electron transfer.