Possible precursors in HCN oligomerization

Ab initio self-consistent field calculations have been used to characterize the electronic structure and to predict geometrical parameters of H2C2N2 isomers. Only three isomers along with the linear (HCN)2 hydrogen-bonded complex are predicted to be lower in energy than two non-interacting HCN monomers. Large scale correlation calculations led to only small refinements in the relative energetics. The most stable isomer is iminoacetonitrile, a fact which enhances the possibility of its rôle in HCN oligomerization. However, this isomer has not been spectroscopically characterized in the gas phase and so accurate predictions of equilibrium rotational constants for iminoacetonitrile as well as the other isomers are reported.