The Reaction of Solvated Electrons with Cytosine, 5-methyl Cytosine and 2′-deoxycytidine in Aqueous Solution the Reaction of the Electron Adduct Intermediates with Water, P-nitroacetophenone and Oxygen a Pulse Spectroscopic and Pulse Conductometric Study

Summary

Using conductivity detection, pulse radiolysis experiments showed that solvent protonation of the electron adducts of cytosine, 5-methyl cytosine and 2′-deoxycytidine occurs with rate constants k ≥ 2 × 10⁴M⁻¹s⁻¹. The protonated electron adducts transfer an electron to p-nitroactetophenone (PNAP) with rate constants ranging from 3·5×10⁹ to 5·3·10⁹M⁻¹s⁻¹. The transfer is quantitative (G = 2·7), as shown by conductometric and spectroscopic measurements. In the presence of O₂ no electron transfer to O₂ takes place, implying that O₂ adds to the protonated electron adduct radicals.

No electron transfer from the H- and OH-adducts of the cytosine derivatives, either to PNAP or to O₂, takes place near neutral pH. It is suggested that the differences in the reaction behaviour of the H-adduct radicals and the protonated electron adduct radicals towards PNAP can be accounted for if different radicals are formed by H-addition and protonation of the electron adduct. The H atoms most probably add to the C-5-C-6 double bonds, whereas the electron adducts are protonated at N-3 and/or 0-2.