Natural bond orbital analysis of some para-substituted N-nitrosoacetanilide biological molecules

Abstract

Theoretical study of several para-substituted N-nitrosoacetanilide biological molecules has been performed using density functional B3LYP method with 6-31G(d,p) basis set. Geometries obtained from DFT calculation were used to perform natural bond orbital analysis. The p characters of two nitrogen natural hybrid orbital (NHO) σN3–N2 bond orbitals increase with increasing σp values of the para substituent group on the benzene, which results in a lengthening of the N3–N2 bond. The p characters of oxygen NHO σO1–N2 and nitrogen NHO σO1–N2 bond orbitals decrease with increasing σp values of the para substituent group on the benzene, which results in a shortening of the N2=O1 bond. It is also noted that decreased occupancy of the localized σN3–N2 orbital in the idealized Lewis structure, or increased occupancy of \( \sigma_{\rm N3-N2}^{\ast}\) of the non-Lewis orbital, and their subsequent impact on molecular stability and geometry (bond lengths) are also related with the resulting p character of the corresponding nitrogen NHO of σN3–N2 bond orbital.