Structure of radicals derived from hydroxypyrimidines in aqueous solution

Abstract

EPR spectra of radicals derived from the three isomeric trihydroxypyrimidines and from 2-hydroxypyrimidine were obtained either in reduction or oxidation conditions at various pH values. Additionally, three other pyrimidine derivatives, 2-thiobarbituric acid, 2-amino-4,6-dihydroxypyrimidine and 2-methyl-4,5,6-trihydroxypyrimidine, were studied in the same conditions. Reduced radicals were produced by reaction of the pyrimidines with the hydrated electron, the hydrogen atom and with the CO₂˙⁻ radical. In these conditions, the electron adducts as well as CO₂˙⁻ adducts were identified in most cases. Oxidized radicals were obtained by reaction of the substrates with OH˙, O˙⁻, SO₄˙⁻, and Br₂˙⁻ radicals. The radicals detected and studied were either of the OH-adduct type or radicals derived from its dehydration. The radicals were investigated by using in situ radiolysis and photolysis EPR techniques.