N-Substituent effects on the stability of ketenimines

A homodesmotic reaction was designed to study N-substituent effects on the stability of ketenimines. A good correlation (SE1=-12.27 chi(BE)+29.81) between N-substituted ketenimine stabilization energies (SE1) and substituent group electronegativity has been found. Both N-substituted and C-beta-substituted ketenimine stabilization energies (SE1 and SE2) have good correlations with Taft's dual-substituent-parameters and modified Swain-Lupton constants. As to N-substituent and C-beta-substituent effects on the stability of ketenimines, sigma-donors stabilize ketenimines while sigma-acceptors destabilize them; pi-acceptors stabilize ketenimines while pi-donors destabilize them.