Issue 35, 2010
From the journal:

Physical Chemistry Chemical Physics

The catalytic effect of water on the keto–enol tautomerism. Pyruvate and acetylacetone: a computational challenge†

Giuliano Alagona,*a   Caterina Ghioa  and  Peter I. Nagyb  

* Corresponding authors

a CNR-IPCF, Molecular Modelling Lab, Via Moruzzi 1, I-56124 Pisa, Italy
E-mail: G.Alagona@ipcf.cnr.it
Fax: +39 050 3152442
Tel: +39 050 3152450

b Center for Drug Design and Development and the Department of Medicinal and Biological Chemistry, The University of Toledo, Toledo, OH, USA
E-mail: pnagy@utnet.utoledo.edu
Fax: +1 419-530-7946
Tel: +1 419-530-1945

Abstract

The catalytic effect of explicit water molecules on the keto–enol tautomerism in a system of biological interest (enolpyruvate) has been investigated at the B3LYP/6-31++G** level by exploring the potential energy surface in the presence of 1 or 2 water molecules and comparing the energy profiles to the direct tautomerisation one. The water-assisted mechanisms turned out to be more favourable than the direct ones, in agreement with what occurred for the acetylacetone tautomerism in the presence of a single water molecule. To compare the behaviour of water in pyruvate and in acetylacetone, the two-water-assisted mechanism has been also examined for the latter at the B3LYP/6-31G* level. A number of stationary points for both compounds in vacuo and in the presence of explicit water molecules have been computed with DFT coupled to larger basis sets and at the MP2 level. Two diketo forms more stable than any of the keto–enol tautomers have been located, while for pyruvate the keto form is always more favourable than the enol one. The equilibrium constant for acetylacetone tautomerisation has been computed with high accuracy, performing a complete basis set extrapolation for the relative internal energy, to determine whether the quality of the method/basis set is responsible for the earlier modest agreement with the experimental value. Monte Carlo and molecular dynamics simulations helped characterize the solution structure and association features in the 0.03–0.22 molar concentration range.

Graphical abstract: The catalytic effect of water on the keto–enol tautomerism. Pyruvate and acetylacetone: a computational challenge

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Article information

DOI
https://doi.org/10.1039/C003999C
Article type
Paper
Submitted
09 Mar 2010
Accepted
22 Jun 2010
First published
02 Aug 2010

Phys. Chem. Chem. Phys., 2010,12, 10173-10188

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The catalytic effect of water on the keto–enol tautomerism. Pyruvate and acetylacetone: a computational challenge

G. Alagona, C. Ghio and P. I. Nagy, Phys. Chem. Chem. Phys., 2010, 12, 10173 DOI: 10.1039/C003999C

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