Energetics and cooperativity in three-center hydrogen bonding interactions. II. Intramolecular hydrogen bonding systems

A comprehensive ab initio study was conducted on a series of amide structures containing intramolecular two- and three-center H-bonding interactions. The superior strength of a two-center H bond in a six-membered ring as opposed to a five-membered ring was demonstrated by a consortia of H-bonding indicators. The results show that the relative stability of isomers containing a H bond does not necessarily parallel the strength of the H-bond itself.