Structures and Vibrational Spectra of the Hydrogen-Bonded Complexes Between Nitrous Acid and Acetone: Ab Initio and DFT Studies |
| |
Authors: | Yordanka Dimitrova |
| |
Affiliation: | 1. Institute of Organic Chemistry, Center of Phytochemistry, Bulgarian Academy of Sciences , Sofia, Bulgaria yordankadimitrova@hotmail.com |
| |
Abstract: | ABSTRACT The structures, stability, and vibrational spectra of the binary complexes formed between acetone and nitrous (trans and cis) acid have been investigated using ab initio calculations at the SCF and MP2 levels and B3LYP calculations with 6-311++G(d,p) basis set. Full geometry optimization was made for the complexes studied. It was established that the complex (CH3)2CO···HONO-trans is more stable than the complex (CH3)2CO···HONO-cis by 0.5–0.8 kcal·mol?1. The accuracy of the calculations has been estimated by comparison between the predicted values of the vibrational characteristics (vibrational frequencies and infrared intensities) and the available experimental data. It was established, that the methods, used in this study are well adapted to the problem under examination. The predicted values with the B3LYP/6-311++G(d,p) calculations are very near to the results, obtained with MP2/6-311++G(d,p). The calculated frequency shift Δν(O[sbnd]H) for the complex (CH3)2CO···HONO-trans (1A) is larger than for the complex (CH3)2CO···HONO-cis (1B). In the same time the intensity of this vibration increases dramatically upon hydrogen bonding. The calculated increase for the complex 1A is up to 15 times and for the complex 1B is up to 30 times. The changes in the vibrational characteristics (vibrational frequencies and infrared intensities) of (CH3)2CO upon the complexation are more insignificant than the changes in the vibrational characteristics of HONO-trans and HONO-cis. |
| |
Keywords: | ab initio and DFT calculations acetone-nitrous acid complexes structures vibrational spectra |
|
|