title: E.s.r. studies of sulphur-substituted pyrimidines. 2-thio-5-carboxyuracil at 77 K.
abstract: Single crystals of 2-thio-5-carboxyuracil were irradiated and studied at 77 K with e.s.r. spectroscopy. Five resonances were observed and related to the sulphur atom in the 2 position of the pyrimidine ring. Three of the resonances have been assigned to three conformations of a radical formed by hydrogen abstraction from N1. The principal values for the nitrogen coupling are 9-7, 0-0 and 0-0 gauss. The g tensor principal values are 2-173, 1-997 and 1-990 for the dominant conformation of this radical. Two other radicals could not be identified unambiguously.
mesh_terms: D004578:Electron Spin Resonance Spectroscopy; D005609:Free Radicals; D005615:Freezing; D011830:Radiation Effects; D014498:Uracil / Q000031:analogs & derivatives / Q000528:radiation effects*
chemical_list: D005609:Free Radicals; D014498:Uracil