How Additives Enable Site–Selective Hydrogen Atom Transfer in Alcohols: Critical Roles of Intrinsic Charge Transfer and Peripheral Electrostatic Interactions

The roles of different types of additives or cocatalysts in modulating the hydrogen atom transfer (HAT) process of alcohols are computationally investigated. The approach of energy decomposition analysis is employed to dissect intermolecular interactions between radicals and CH substrates, thereby identifying key factors governing HAT site selectivity. The results reveal that different additives can alter the intermolecular interactions, leading to distinct factors governing HAT site selectivity. Specifically, ZnCl 2 promotes αCH bond activation by enhancing charge transfer from the αCH σ orbital to the singly occupied molecular orbital of nitrogen. Borinic acid and H 2 PO 4 anion favor αCH abstraction by introducing peripheral electrostatic interactions that stabilize the positively charged radical species.