Reactions of Thermally Generated 1-Adamantyl and Di(1-adamantyl)ketyl Radicals in Toluene

Article abstract of DOI:10.1021/jo00290a044

Thermolysis of tri(1-adamantyl)methanol in toluene at 145-185 deg C gives bibenzyl, di(1-adamantyl)ketone, di(1-adamantyl)methanol and a cross-product, 1,1-di(1-adamantyl)-2-phenylethanol, in yields which depend on the temperature and the isotopic composition of the solvent.In the presence of benzophenone the intermediate di(1-adamantyl)ketyl radical transfers hydrogen, giving ketone and the hydroxybenzhydryl radical, the cross-product then being 1,1,2-triphenylethanol.The cage effect (0.38-0.415) has been determined by studying thermolysis in deuterium labeled toluene.In normal toluene almost all the secondary alcohol is formed from Ad2C*OH by hydrogen abstraction from the solvent, whereas in deuterated toluene 22-32percent results from self-disproportionation of ketyl radicals, showing that there is a substantial kinetic isotope effect on hydrogen abstraction.Kinetic modeling of the reaction by means of a rapid, iterative procedure based on the steady-state approximation suggests values in the range 6.0-7.4, decreasing as the temperature rises.