Theoretical Calculations on the Conformational/Tautomeric Equilibria for Small Molecules in Solution

Peter Nagy

doi:10.4172/2167-0501.s4-001

Abstract

The prevailing conformation and/or tautomeric form of a species may affect the product in chemical reactions. Determination of the predominant ligand structure is also important in theoretical drug design, where the goal is finding the best fit between the structurally flexible ligand and the receptor. The present review surveys the computational problems encountered in structure determination of small organic molecules in solution. The discussed issues include the method of the geometry optimization, the needed level of theory and basis set, choice of the modeling parameters, and the determination of the relative standard chemical potentials for estimating the equilibrium constant in relation to the molar concentration of the participants through the chemical transformation.

Highlights

This review intends to survey theoretical calculations for conformational and/or tautomeric equilibria of small organic molecules in solution
Ab initio SCRF solvation energy calculations pointed out the gradual stabilization of the keto form with larger dipole moment in dielectrics characterized by ε=2 and 36
This time period was selected, because computer resources allowing satisfactorily high-level theoretical calculations for in-solution processes became available for a large fraction of the research community only in about the nineties

Summary

Introduction

This review intends to survey theoretical calculations for conformational and/or tautomeric equilibria of small organic molecules in solution. In the forthcoming survey, hydrogen bonds will be accepted on the basis of the H...X distance Another important field of the conformational changes is the possibly back-and-forth flip from the chair structure to the twist-boat (skew) form for six-member saturated rings. According to the best knowledge of the author, no comprehensive review has been published so far on the field specified in the title of this paper This title allows for a survey of the wide research activity of the scientific community, only a more modest goal has been set forth as an aim in this review: consideration of the theoretical studies on the in-solution conformational and tautomeric equilibria for small, biological important molecules including mainly 1,2-disubstituted ethanes, ortho phenols, and five- and six-member ring systems. The recent publications include references to papers reporting earlier stages of the methods

Methodology

H H3C C CH3

Findings

Concluding Remarks