title: The reactions of the hydroxymethyl radical with 1,3-dimethyluracil and 1,3-dimethylthymine.
abstract: Hydroxymethyl radicals .CH2OH, generated by the radiolysis of methanol (0.5 mol dm-3) in N2O-saturated aqueous solutions, were reacted with 1,3-dimethyluracil or 1,3-dimethylthymine (10(-3) mol dm-3). The products were identified and their G values determined. It has been concluded that in 1,3-dimethyluracil .CH2OH attack occurs only at C(6) while in 1,3-dimethylthymine there is partitioning between addition (two-thirds) and H-abstraction from the C(5)-methyl group (one-third). A rate constant for CH2OH addition to 1,3-dimethyluracil of about 10(4) dm3 mol-1 s-1 is estimated. Complexities that may arise in the radiolysis of pyrimidines such as 1,3-dimethylthymine, apparently as a consequence of the formation of 5-alkylidenepyrimidines, are discussed. A value of 0.15 has been estimated for the disproportionation/combination ratio for the hydroxymethyl radical self-termination reaction.
mesh_terms: D002849:Chromatography, Gas; D004247:DNA / Q000528:radiation effects; D005609:Free Radicals; D006878:Hydroxides; D017665:Hydroxyl Radical; D011854:Radiochemistry; D013941:Thymine / Q000031:analogs & derivatives*; D014498:Uracil / Q000031:analogs & derivatives*
chemical_list: D005609:Free Radicals; D006878:Hydroxides; D017665:Hydroxyl Radical; C039199:N,N-dimethylthymine; D014498:Uracil; C002451:1,3-dimethyluracil; D004247:DNA; D013941:Thymine