Study of Mechanism Keto-Enol Tautomerism (isomeric reaction) Structure Cyclohexanone by Using Ab initio Molecular Orbital and Density Functional Theory (DFT) Method with NBO Analysis

Initial quantum mechanic studies and density function theory (DFT) in the level of HF/6-311+G**, B3LYP/3-21+G* and B3LYP/6-311+G** on Keto-Enol Tautomerism (isomeric reaction) cyclohexanone structure, that results shows that activation energy for this reaction equal 64.6143(kcal.mol-1) and transition state has the highest energy level equivalent whit -194354.27(kcal.mol-1) that due to breaking of C-H bond and composing of O-H bond. The results of NBO analysis of showed that the bond π are in resonance condition with lone-pair electrons oxygen of and therefore providing enol state and the transition state in these reactions usually is the structure between ketone state and enol state. Bond order and density of electrons aren’t the same in structures enol state, transition state and ketone state. Also tautomerism cyclohexanone structure is a kind of endothermic isomeric reaction.