Steady State Radiolysis of Aqueous Aerated Solutions of 5,6-Dihydrothymine. Identification of the Major Degradation Products

The major radiation-induced degradation products of 5,6-dihydrothymine (1) in aqueous solutions saturated either with O2 or N2O/O2 (75/25 v/v) were identified as thymine (10), the trans-and cis-isomers of 6-hydroperoxy-5,6-dihydrothymine (5, 7), 5-hydroperoxy-5,6-dihydrothymine (9), and their corresponding hydroxy derivatives (4, 6, 8). The formation of these compounds is explained in terms of initial H-abstraction from the C(5) and C(6) carbons which gives rise respectively to the transient 5-yl and 6-yl radicals. Thymine hydroxy-hydroperoxides (11-14) and their decomposition products (17-20), which are derived from hydroxyl radical attack at the 5,6-ethylenic bond of thymine (10), were also characterized.