The catalytic effect of water on the keto-enol tautomerisation reaction of thioformic acid

Abstract

A detailed theoretical study of the proton transfer in the HC(O)SH ⇌ HC(S)OH reaction in the gas phase and catalysed by water is presented. The mechanism is analysed within the framework provided by the reaction force; structural parameters and electronic properties are analysed along the reaction path. A complete description of the electronic activity that takes place along the reaction coordinate emerges when analysing the reaction electronic flux, thus allowing one to make a clear distinction between the two reaction mechanisms. Results show that the barrier height of the water-catalysed proton transfer reaction is about a third of that for the intramolecular reaction, thus emphasising the importance of the catalytic effect of H₂O.

Keywords:

• reaction force
• reaction electronic flux
• tautomerisation reaction
• thioformic acid

Acknowledgements

This work was supported by Fondecyt through project 1090460. F.D. thanks CONICYT for a Doctoral and Apoyo de Tesis fellowships and to L'OREAL-UNESCO for the Woman in Science 2009 award.