Semiempirical Method MNDO for the Evaluation of the Effect of Different Substituents at the Imine-Carbon Position on the Acetaldemine-Vinylamine Tauotomerization and Comparison to the Substitution at α-Position

Abstract

MNDO calculations have been employed to study the effect of some substituents of the acetaldemine-vinylamine tautomeric system at the imine-carbon position of CH 3 CXNH, where X = H, F, CN, NH 2 , NO 2 , BH 2 , CH 3 and CF 3 . It is found that the substitutents F, NH 2 and NO 2 encourage the formation of the enamine tautomer. The substitutents CN, CH 3 , CF 3 and BH 2 encourage the formation of the imine tautomer. Isodesmic reactions, free energy change (∆G), charge distribution and energy gap (E g ) between HOMO and LUMO were used to prove these findings. Resonance stabilization was a major factor in the determination of the most stable tautomer. These results were compared with previous work on the substitution at the σ -carbon position.