Correct Interpretation of How Tunneling Proceeds at Low Temperatures in the Proton Transfer Reactions Involving Thiotropolone: A Comment

摘要

In their recent Communication Jose and Datta have performed canonical variational transition-state theory calculations with small-curvature tunneling corrections for tunneling (CVT/SCT) to describe the intramolecular proton transfer processes in thiotropolone and tropolone (Reaction (1) of tautomers la/lb and Reaction (3) of tautomers 3a/3b; see Scheme 1 taken form the original Communication by Jose and Datta). These authors conclude that at temperatures below T=240 K proton transfer is faster in thiotropolone than in tropolone, and that for the former molecule tunneling represents about 99% of the total process even at room temperature. The present Corrrespondence shows that their CVT/SCT calculations are incorrect, and that the conclusions derived from those calculations are erroneous and easily refuted by basic arguments of how tunneling proceeds in a chemical reaction. The Correspondence also provides the correct interpretation of tunneling effects in Reactions (1) and (3). The same arguments are also valid for the deuterium transfer in the two compounds (see Scheme 1), and therefore they are not discussed here. Details about the CVT/SCT calculations are given in the Supporting Information.