Abstract: The tautomeric mechanism of acetaldehyde into vinyl alcohol and ketene into ethynol have been investigated theoretically by ab initio MO method and AM_1 MO method respectively. The geometry of various critical points in reaction pathways had been optimized on the corresponding potential energy surfaces. The reaction heat and the rate constant of the two reactions were also calculated. The results show that the stability of vinyl alcohol is higher than ethynol while the reaction rate of acetalde-hyde into vinyl alcohol is lower than that of ketene into ethynol.

Key words: Vinyl alcohol, Ethynol, Tautomeric reaction, Ab initio, AM1 method