Hydrogen bond cooperativity in polyols: A DFT and AIM study

Density functional theory calculations, and atoms in molecules analyses are performed to investigate both the strength and the cooperative enhancement of intramolecular OH⋯OH hydrogen bonding interactions occurring in polyols. The relative strength of the OH⋯OH interaction is evaluated in two basic model systems: 1,3-propanediol, and 1,8-napthalenediol. The backbone of the former model is aliphatic, whereas that of the latter is aromatic. The cooperative enhancement of the OH⋯OH interaction is evaluated by extending symmetrically the polyol chain of each model system on both sides of the interaction in the basic unit. Specifically, we considered polyols with an odd number of H bonds running from one to eleven depending on the size of the polyol. The polyols are chosen so that there is a carbon atom located in between adjacent hydroxyl groups. Pertinent geometrical, and topological parameters are used as primary indicators of H bond strength, and consequently for cooperativity assessment. Also, the Lippincott and Schroeder hydrogen bond model, LS-HB, is used to estimate intramolecular hydrogen bonding energies.