H. Tavakol, Computational Study of Thiohydroxamic Acids Tautomers 2^nd Internatnal conference on mathematical chemistry, Kashan, Iran, April 2009.

Abstract

In recent years, computational chemistry has been one the major topics in chemistry. In addition, thiohydroxamic acids have very important properties and are among the most well studied compounds due to their significance in complexing with transition metals since 19^th century [1]. They play various roles in analytical and biological chemistry. In addition, the tris-chelates of thiohydroxamic acids and Fe³⁺ are believed to participate in bacterial iron-transport systems [2]. They are also capable to trap free radicals [3] that there is no doubt that the inhibitory effect is in correlation with chelation of the catalytic metal center by the hydroxamate function. Also, they have been used as polymer regulators [4]. The properties of the thiohydroxamate system have been reviewed recently [5]. In spite of their biological importance, very little theoretical work [6] is done on this system.

Although the growing interest in the study of  thiohydroxamic  functional groups is observed, but the structures of thiohydroxamic  acids are still the subject of many controversies. Because the potential for tautomerism and transition state energy and properties has been recognized as a particular characteristic of thiohydroxamic acids and this aspect has not been investigated fully. Therefore, in this work, we have attempted a thorough analysis of all possible tautomers of some thiohydroxamic acids.

In most of previous literatures, Thiohydroxamic acids reports in two tautomeric forms, first is keto or N-hydroxy thioamide form a and second is iminothiol or α-merchapto oxime b form. In addition, they may exist in third tautomeric form that can be explained as α-nitroso thiol c form. We used all these tautomers in our calculations and we have selected nine different thiohydroxamic acids for estimating their properties by computational method.  Three possible tautomers of all selected compounds considered in this work