On the C 2 H 2 l + potential energy hypersurface. An ab initio study

The study of the C2H2l+ cation at several levels of ab initio theory reveals the existence of four stationary points, three of them are characterized as minima and another as a transition state; the 1-iodovinyl cation is the global minimum, the cyclic iodonium ion is very close in energy to the 1-iodovinyl cation and the transition state connecting the 1-iodovinyl cation and the cyclic iodonium ion is very high in energy.