ESR parameters and the structures of the free radicals produced from the reduction of cytosine in nonaq. solns. were studied by an electrochem. method in conjunction with ESR. The structure of the radical with ESR parameters of g = 2.002, aN = 1.05 G, a1H= 2.1 G, a2H= 1.05 G was determine In the course of studies on the kinetic behavior of this radical, a new phenomenon was observed After the electrochem. reduction of cytosine was stopped, the concentration of this radical 1st increased and then decreased, through a max. in the whole growth and decay process. Thus, after the electrochem. reduction ceased, a subsequent chem. reaction continued to generate the radical as well. A reaction mechanism was suggested in which the 2-electron reduction product can react with the substrate cytosine, according to a reaction scheme presented in the text. Kinetic parameters k1 (4.9 ?10-2 dm3/mol/s) and k2 (7.7 dm3/mol/s) were determine The experimental curves coincided well with curves derived from the numerical solution of the theor. model.

Key words: OXIDATION REDUCTION REACTION, REACTION MECHANISM, REACTION KINETICS, STRUCTURAL ANALYSIS, ELECTRON SPIN RESONANCE, CYTOSINE, ELECTROCHEMICAL REACTION