Hydrogen and proton exchange at carbon. Imbalanced transition state and mechanism crossover

Abstract

Using the remarkable study of C–H oxidation of substituted fluorenyl-benzoates as an example, we have shown that a mechanism crossover takes place upon decreasing the driving force, from a CPET pathway to a PTET pathway.

Statistical analysis of C–H activation by oxo complexes supports diverse thermodynamic control over reactivity

“…65,66 In this case, the intermediates arise from proton transfer and electron transfer, and when either Δ G PT or Δ G ET lowers in energy the transition state can adopt structural and electronic components of these intermediates resulting in a lower barrier height. While the use of these classical structure–energy relationships to analyse PCET reactions has been questioned recently, 26,27 proton transfer and electron transfer states and their energies also have roles in nonadiabatic rate theories of PCET which treat proton transfer in a quantum mechanical fashion. 67,68 Therefore, the use of Δ G PT and Δ G ET to predict barrier heights of PCET is consistent with prior theoretical foundations.…”

Proton-Coupled Electron Transfer Guidelines, Fair and Square

“… 69 It has also been suggested that the larger slope when the base was varied is because of a simultaneous PTET mechanism. 70 …”

From Synthetic to Biological Fe4S4 Complexes: Redox Properties Correlated to Function of Radical S‐Adenosylmethionine Enzymes

“…As demonstrated in Refs. [37][38][39][40][41][42][43][44], H-atom-abstraction (HAA) reactivity and selectivity are strongly influenced by the interplay of redox and acidobasic components of the HAA thermodynamic force, which are usually inter-dependent so that a lower E°is compensated to some extent by a higher pK a and vice versa. Thus, to probe the 5'-dAdo * properties relevant for enzymatic HAA reactivity, we first analyze electrochemical behavior of 5'-dAdo * in aqueous solution and then we compare it with its behavior in models of the [Fe 4…”