Kinetic applications of electron paramagnetic resonance spectroscopy. III. Self-reactions of dialkyl nitroxide radicals

Bimolecular rate constants and activation parameters have been measured for the self-reactions of several dialkyl nitroxides in a number of solvents. It has been shown that there is a large deuterium isotope effect on the reaction if the hydrogens on the α-carbons are replaced by deuterium. The results are consistent with a mechanism involving the reversible formation of a diamagnetic nitroxide dimer and its slow decomposition to a hydroxylamine and a nitrone. The equilibrium constant for dimer formation has been determined with (CH3-CD2)2NO· in isopentane and in CF2Cl2. The analogy between the self-reactions of nitroxides and of peroxy radicals is pointed out.