Cooperative effects in regular and bifurcated intramolecular OH⋯OC interactions: A computational study

Density functional theory calculations are performed to investigate the stabilizing or destabilizing cooperative effects in regular and bifurcated intramolecular OH⋯OC hydrogen bond (H bond) interactions. Regular H bonds are examined in two model hydroxyketones: 1-hydroxy-3-butanone, and 5-hydroxy-4-quinolone. Bifurcated H bonds, OH⋯O(C)⋯HO, are examined in two model systems: 1,5-dihydroxy-3-pentanone, and 1,8-dihydroxy-9-acridinone. Changes in the strength of the H bonds are examined upon extending the backbone of each model system with polyol chains of varying size. Stabilizing cooperative effects are seen in both the regular and the bifurcated H bonds. When compared with corresponding regular H bond counterparts, the bifurcated H bond model systems exhibit destabilizing cooperative effects with polyol addition. It is found that, for comparable systems, the OH⋯OC interaction is strengthened more by stabilizing cooperative effects than it is weakened by destabilizing cooperative effects.