Hydrogen and Proton Exchange at Carbon.Imbalanced Transition State and Mechanism Crossover

Abstract

A recent remarkable study of the C-H oxidation of substituted fluorenyl-benzoates together with the transfer of the proton to an internal receiving group by means of electron transfer outer-sphere oxidants, in the noteworthy absence of hydrogen-bonding interactions, is taken as example to uncover the existence of a mechanism crossover, making the reaction pass from a CPET pathway to a PTET pathway as the driving force of the global reaction decreases. This was also the occasion to stress that considerations based on “imbalanced” or “asynchronous” transitions states cannot replace activation/ driving force models based on quantum mechanical treatment of both electron and transferring proton.