Substituent effects on stability of ketenimines

Abstract

An isodesmic reaction was designed to study substituent effects on the stability of ketenimines. A good correlation (ΔE = –11.31 χ_BE + 31.07) between substituent group electronegativity and the stability of ketenimines has been found. Electropositive substituents stabilize ketenimines while electronegative substituents destabilize ketenimines. Ketenimines gain extra stabilization when their substituents are π acceptors, such as AlH₂, BH₂, OCH–, HO₂C–, CN, NO₂, and HSO₂, resulting in the existence of cyano-cation resonance structures. An ynamine resonance structure plays an important role in ketenimine with a lithium substituent.