Hydroxylic Solvents as Hydrogen Atom Donors in Radical Reactions

Hydrogen‐transfer reactions between methyl radicals and protic solvents, such as water and ethanol, have been studied at the G3(MP2)‐RAD level of theory. The typically high barriers for hydrogen ion from the OH group are lowered dramatically on complexation of protic solvents with BMe3. The barrier lowering is found to be a consequence of the unique properties of trialkylboranes, acting as Lewis acids towards the closed‐shell solvent, but as electron donors towards the evolving oxygen‐centered radicals.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)