Alkoxy nitroxide radicals from photolysis of nitropyridines: a kinetic investigation by electron spin resonance spectroscopy

Triethylsilyloxy nitroxide radicals obtained by photolysis from the three isomeric nitropyridines have been investigated by e.s.r. spectroscopy. The kinetic study showed a first-order decay of the radicals; the concentration was found to depend upon the square root of the light intensity and therefore a reaction mechanism is postulated involving the reversible formation of a diamagnetic dimer. Proof of this was obtained by rapidly raising the temperature during the course of radical decay.