Radical formation in salts of pyrimidines III. Cytosine . H2O cyrstals.

The radicals produced by X-irradiation at 77 K and at 300 K in cytosine monohydrate crystals have been analysed by electron-spin-resonance (e.s.r.) spectroscopy. Three radicals have been identified at 77 K: the anion radical and the cation radical of the cytosine molecule, together with the radical resutling from H-abstraction from the nitrogen N1. Irradiation at 300 K produces radicals resulting from H-adition at three different positions of the cytosine molecule. These are the C5-addition radical, the C6-addition radical, and the O2-addition radical. The results are compared with those found previously by other authors.