An EPR study of 1-adamantylmethyl radicals

Abstract

The 1-adamantylmethyl, di(1-adamantyl)methyl, and tri(1-adamantyl)methyl radicals have been prepared by photolysis of hexabutylditin in presence of the corresponding bromide, the 1-adamantylhydroxymethyl radical by photolysis of di-tert-bulyl peroxide in presence of 1-adamantylmethanol, and the di-1-adamantylketyl radical anion by photolysis of di-1-adamantyl ketone in presence of sodium–potassium alloy. The EPR ¹H and ¹³C hyperfine coupling constants which are observed in these radicals and in the tetra-1-adamantylcyclobutadiene radical cation are discussed in terms of the structures of the radicals.

The di-1-adamantylmethyl radical decays in cyclopentane at 310 K and in toluene at 180–240 K by clean pseudo first-order kinetics. The reaction is much faster in the latter solvent, implying that it involves abstraction of benzylic hydrogen. At 190 K in pentane, the decay shows second-order kinetics. The decay of the tri-1 -adamantylmethyl radical shows more complicated behaviour.