Conformational stability and vibrational spectrum of glyoxilic acid oxime predicted from ab initio study

Abstract

The conformational stability of glyoxilic acid oxime (HOOC–CH–NOH) (GAO) and its anions has been studied by ab initio calculations at different levels of the theory, HF/6-311G ∗∗, MP2/6-311G ∗∗ and B3LYP/6-311G ∗∗. Geometry optimization was performed for 16 conformations of GAO and five anions in C s symmetry. The interconversion pathways for the four lowest energy conformers as well as the corresponding transition states have been investigated using QST3 and IRC techniques. The minima and the transition states obtained were estimated by calculations of the vibrational frequencies. The energy barriers of three interconversions, ectt–ecct, ectt–ettt and ectt–zccc, have been estimated. Vibrational spectra and IR intensities of the lowest energy conformers, zccc, ectt, ettt and ecct, have been calculated and discussed at HF/6-311G ∗∗ optimized geometries.