Substituent effect on structure, electron density, and intramolecular hydrogen bonding in nitroso‐oxime methane

Abstract

Density functional calculations with Beck’s three-parameter hybrid method using the correlation functional of Lee, Yang, and Parr (B3LYP) were carried out for investigation of the intramolecular hydrogen bond strength in Nitroso-oxime methane and its derivatives. Also, vibrational frequencies for them were calculated at the same level of theory. The p-electron delocalization parameter (Q) and as a geometrical indicator of a local aromaticity, the geometry-based harmonic oscillator measure of aromaticity index has been applied. Additionally, the linear correlation coefficients between substituent constants and selected parameters in R position have calculated. The obtained results show that the hydrogen bond strength is mainly governed by the resonance variations inside the chelate ring induced by the substituent groups. The topological properties of the electron density distributions for OAHO intramolecular bridges have been analyzed in terms of the Bader theory of atoms in molecules (AIM). Correlations between the H-bond strength and topological parameters have been also studied. The electron density (q) and Laplacian (!2 q) properties, estimated by AIM calculations, show that OH bond have low q and negative (!2 q) values (consistent with covalent character of the HBs), whereas OAH bond have positive (!2 q) Furthermore, the analysis of hydrogen bond in this molecule and its derivatives by quantum theory of natural bond orbital (NBO) methods fairly support the ab initio results. Natural population analysis data, the electron density, and