67934-78-5Relevant articles and documents
Fenton chemistry of 1,3-dimethyluracil
Theruvathu,Aravindakumar,Flyunt,Von Sonntag,Von Sonntag
, p. 9007 - 9014 (2007/10/03)
Hydroxyl radicals were generated in the Fenton reaction at pH 4 (Fe2+ + H2O2 → Fe3+ + ?OH + OH-, k ≈ 60 L mol-1 s-1) and by pulse radiolysis (for the determination of kinetic data). They react rapidly with 1,3-dimethyluracil, 1,3-DMU (k = 6 × 109 L mol-1 s-1). With H2O2 in excess and in the absence of O2, 1,3-DMU consumption is 3.3 mol per mol Fe2+. 1,3-DMUglycol is the major product (2.95 mol per mol Fe2+). Dimers, prominent products of ?OH-induced reactions in the absence of Fe2+/Fe3+ (Al-Sheikhly, M.; von Sonntag, C. Z. Naturforsch. 1983, 31b, 1622) are not formed. Addition of ?OH the C(5)-C(6) double bond of 1,3-DMU yields reducing C(6)-yl 1 and oxidizing C(5)-yl radicals 2 in a 4:1 ratio. The yield of reducing radicals was determined with tetranitromethane by following the buildup of nitroform anion. Reaction of 1 with Fe3+ that builds up during the reaction or with H2O2 gives rise to a short-chain reaction that is terminated by the reaction of Fe2+ with 2, which re-forms 1,3-DMU. In the presence of O2, 1.1 mol of 1,3-DMU and 0.6 mol of O2 are consumed per mol Fe2+ while 0.16 mol of 1,3-DMU-glycol and 0.17 mol of organic hydroperoxides (besides further unidentified products) are formed. In the presence of O2, 1 and 2 are rapidly converted into the corresponding peroxyl radicals (k = 9.1 × 108 L mol-1 s-1). Their bimolecular decay (2k = 1.1 × 109 L mol-1 s-1) yields ～22% HO2?/O2?- in the course of fragmentation reactions involving the C(5)-C(6) bond. Reduction of Fe3+ by O2?- leads to an increase in ?OH production that is partially offset by a consumption of Fe2+ in its reaction with the peroxyl radicals (formation of organic hydroperoxides, k ≈ 3 × 105 L mol-1 s-1; value derived by computer simulation).
