Radical formation in salts of pyrimidines. I. 1-methyluracil. HBr crystals.

Radicals produced by X-irradiation at 77 K of 1-methyluracil. HBr crystals have been analysed by electron spin resonance spectroscopy. The results are compared with those obtained on 1-methyluracil crystals. Four radicals have been identified, two of which are present only in 1-methyluracil. HBr crystals: the C6-addition radical and the pyrimidine--anion radical. Warming-up experiments have been performed in order to study the secondary radical reactions. The different mechanisms proposed for the radiolysis of DNA constituents in the solid state are discussed in connection with these findings.