The nature of the NO bond in amine oxides

Abstract

AbstractDespite the ubiquitous presence of amine oxides in chemistry, there is no consensus about the nature of the NO bond in these compounds. In this work, we have used electron density analysis to investigate the nature of this bond in substituted amine oxides, R3NO, and have compared it with the nature of the NO bond in hydroxylamines, R2NOR, and model molecules that have well‐established chemical bond character. The results showed that the NO bond length and relative stability are proportional to the inductive effect of the substituents. Quantum chemical topology, natural bond orbitals (NBO), and natural resonance theory (NRT) analyses indicated that the NO bond is polar covalent in all the studied amine oxides, but the ionic contribution is different. NBO and NRT analyses revealed that molecules with more electronegative substituents have strongly delocalized NO and NR bonds, whereas molecules with electropositive substituents have localized bonds.