Theoretical study on kinetics of ammonia-catalyzed ground-state tautomerization in 2-pyridone: effect of chemical modification

摘要

The effects of chemical modification on the kinetics of GSPT in 6R~2PY-NH_3 (R=NO_2, CF_3, COOH; CH_3, C_2H_5) complex, in which the H atom at C_6 position of 2PY was substituted, were researched in detail at the M06-2X/6-311 + G(d, p) level. The changes of structural parameter, reaction mechanism, and energies of GSPT before and after the replacement with different substituent have been analyzed. GSPT process in the 6R~2PY-NH_3 (R=NO_2, CF_3, COOH; CH_3, C_2H_5) complex preferred to occur via a concerted but asynchronous protolysis pathway regardless of the electronic nature of substituent R. However, the structural parameters, asynchronicity of GSPT, and barrier height were influenced by the different substituent. The Hammett's and Taft's substituent constant had linear correlation with Δ(R~1 + R~2), NBO charges of NH_4 ~+ and ΔΔV.