Vinyl isocyanate and vinylcyano ether: ab initio studies of geometries and conformations

Abstract

Ab initio molecular orbital calculations using the minimal STO-3G basis set have been carried out on vinyl isocyanate. Preliminary calculations employing experimental geometric parameters indicate the existence of two stable conformations: cis and trans, with the latter being of lower energy. Only after geometry optimizations have been carried out is the cis conformer found to be more stable. However, the energy difference is computed to be rather small, namely 0.08 kcal mole −1. Similar results are found for vinylcyano ether using both the minimal STO-3G basis and the split-valence 4-31G basis. The cis-vinylcyano ether optimized STO-3G structure is computed to be greater than 5 kcal mole −1 more stable than the corresponding optimized cis-vinyl isocyanate.