Using pulse radiolysis, we studied the reactions of small radicals (e(aq)(-), OH., N-3(.), and (CH2OH)-C-.) with 3-(mercaptoethyl)chinazoline-2,4-(1H,3H) in aqueous solution. Whereas the solvated electron adds selectively to the carbonyl group near the aromatic moiety, the hydroxyl radical reacts by addition to the aromatic ring as well as by H abstraction at >N(l)H and -SH groups. Also, azide radicals nonspecifically oxidize the aromatic ring, the thiol group, or the thiolate anion and the amine group at N-(l), as identified by subsequent radical products. In contrast, hydroxymethyl radicals (derived from methanol) abstract hydrogen selectively at the thiol group. The thiyl radical formed was used to study the kinetics of H abstraction in the bisallylic positions of linolenic acid. Product transient identification was performed by kinetic analysis as well as by comparison with reactions of molecules with structures less complex than that of the title compound, exhibiting relevant functional groups.