Electron correlation effects on both conventional, O-H…O, and nonconventional, C-H…O, intramolecular hydrogen bonds present in a selected azelaic acid folded conformation were evaluated ab initio using HF and MP2 methodologies. The relative strength of the hydrogen bonds was examined through different indicators derived from geometry, vibrational frequencies, and electron density along the hydrogen bond path. The HF method results in weaker O-H…O and C-H…O hydrogen bonds when compared with the corresponding results using the MP2 method. Additionally, the stability of the folded azelaic conformation is found to depend on the level of theory used. Accordingly, the zero-point corrected energies of the folded conformation relative to a linear conformation are calculated to be +4.46 kcal/mol and -3.67 kcal/mol at the HF and MP2 levels of theory respectively. The positive sign at the HF level indicates that the folded conformation is less stable than the linear conformation, in sharp contrast to the MP2 method, which predicts the folded conformation to be preferred.
Kalata, Sabina; Huang, Alina; and Parra, Ruben
"Correlation Effects on Intramolecular C-H...OH and O-H...O Hydrogen Bond Interactions in Azelaic Acid: an ab initio study,"
DePaul Discoveries: Volume 10, Article 12.
Available at: https://via.library.depaul.edu/depaul-disc/vol10/iss1/12