Pattern of OH Radical Reaction with N6,N6,9-Trimethyladenine. Dehydroxylation and Ring Opening of Isomeric OH Adducts

Article abstract of DOI:10.1021/j100176a056

The OH radical reacts with N⁶,N⁶,9-trimethyladanine (A) in aqueous solution by addition to carbons 4 and 8 of the purine system (k = 8.4 * 10⁹ M^-1 s^-1).The resulting radicals A4OH* and A(OH* undergo elimination of OH(1-) (identified by conductance; k_el = 2*10⁶ s^-1) and ring opening (k = 2.3*10⁵ s^-1), respectively.The two types of reaction have different activation parameters.The (heterolytic) dehydroxylation reaction of A4OH* is inhibited by H(1+) and by OH(1-).The radical cation (the yield per OH* is 50percent) formed by elimination of OH(1-) from A4OH* is oxidizing (with respect to N,N,N',N'-tetramethyl-p-phenylenediamine); in contrast, A8OH* or its ring-opened product is reducing (toward tetranitromethane or viologens).On one-electron oxidation, A8OH* is converted into 8-hydroxy-N⁶,N⁶,9-trimethyladenine, which was measured by HPLC with optical and electrochemical detection.