Theoretical studies on the bonding characteristics and charge topology of a ketene–pyridine ylide

Abstract Ab initio Hartree–Fock (6-31G * ) and density functional (B3LYP/6-31G * ) methods have been used to study the mechanism of the formation of a ketene–pyridine ylide which has been observed by G.G. Qiao, J. Andraos and C. Wentrup (J. Am. Chem. Soc., 118 (1996) 5634). The results show that a complex (COM) is formed first, then the ylide via a transition state (TS). The activation barrier of this reaction is only 2.84 kcal mol −1 at the B3LYP/6-31G * level, which is in good agreement with the experimental fact that the reaction can proceed at 15 K. In addition, the electronic structure and bonding of the stationary points have been analyzed by Bader-type electron density analysis.