Theoretical study on keto–enol tautomerism and isomerization in pyruvic acid |
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Authors: | Younes Valadbeigi Hossein Farrokhpour |
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Institution: | Department of Chemistry, Isfahan University of Technology, , Isfahan, 84156‐83111 Iran |
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Abstract: | Isomerization and tautomerism of 12 isomers of pyruvic acid including 4 keto and 8 enol forms were studied at the MP2 and B3LYP levels of theory using 6‐311++G(2df,p) basis set, separately. Activation energy (Ea), imaginary frequency (υ), and Gibbs free energy (ΔG#) of the considered isomerization and tautomerism reactions were calculated. Interconversion of the enol forms proceeds through two paths: (i) proton transfer and (ii) internal rotation. Activation energies for the proton transfer paths were in the range of 125–145 kJ/mol and for the internal rotation paths were in the range of 5–45 kJ/mol. Keto–enol tautomerism of pyruvic acid proceeds only through proton transfer route and their activation energies were in the range of 200–300 kJ/mol. Effect of microhydration on the transition state structures and activation energies was also investigated. It was found that the presence of a water molecule catalyzes the isomerization and tautomerism reactions of pyruvic acid so that the activation energies decrease. © 2013 Wiley Periodicals, Inc. |
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Keywords: | keto– enol tautomerism pyruvic acid transition state computational methods activation energy internal rotation |
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