Protocovalent N–O bonding in methyl nitrite (CH3ONO) and ethyl nitrite (C2H5ONO). Topological analysis of the electron localization function (ELF) and electron localizability indicator (ELI-D) functions

Topological analysis of the ELF and ELI-D functions has been carried out using DFT and CASSCF methods for cis- and trans-isomers of methyl nitrite (CH3ONO), as well as three conformers of ethyl nitrite (C2H5ONO). The N–O central bond is of protocovalent type and is represented by the V(N) and V(O) attractors (basins), with a population of 0.79/1.15e in CH3ONO and 1.08/1.12e in C2H5ONO. The correspondence between the protocovalent N–O bond and the most favourable dissociation channel, previously observed for nitrous acid (HONO) [9], has been confirmed.