Computational and theoretical approaches for mechanistic understanding: general discussion

Abstract

responded: Experimentally, the competition reactions were performed in a 4 : 1 mixture of dichloromethane:methanol. In methanol, the reactions both proceed more rapidly and also go more to full completion, while dichloromethane was introduced to ensure the solubility of all products. We therefore ran calculations incorporating a correction for pure methanol and a second set (in the supporting information) with pure dichloromethane. Importantly, the trends are identical with these two approaches, but with higher computed barriers in dichloromethane (consistent with the slower reactions observed experimentally). The increased barriers are due to the more difficult Cl À dissociation step (D to E in the paper). We feel justied in emphasizing the results in methanol as other experimental work has shown similar C-H activation reactions to be promoted upon the addition of just a few equivalents of methanol. This may be due to specic solvation of the Cl À anion as it dissociates. The computed barriers in methanol are also more consistent with most of the reactions proceeding at a reasonable rate at room temperature experimentally. We also found the balance between intramolecular AMLA/CMD and an external CMD process was solvent dependent: in methanol the former is clearly favoured, whereas in dichloromethane external CMD can become competitive, especially for the more electron-withdrawing substituents.

The continuum of carbon–hydrogen (C–H) activation mechanisms and terminology

“…This Perspective was prompted by a discussion at the Faraday meeting in 2019 between Love, Eisenstein, Macgregor, Davies, Lloyd-Jones and others 23 . A point of agreement was that the use of terminology to describe and differentiate between the processes involved in C-H bond cleavage within the community was being used inconsistently.…”