PT - JOURNAL ARTICLE AU - Jovanovic, S V AU - Neta, P AU - Simic, M G TI - One-electron redox reactions of pyrazolin-5-ones. A pulse radiolysis study of antipyrine and analogues. DP - 1985 Oct 01 TA - Molecular Pharmacology PG - 377--380 VI - 28 IP - 4 4099 - http://molpharm.aspetjournals.org/content/28/4/377.short 4100 - http://molpharm.aspetjournals.org/content/28/4/377.full SO - Mol Pharmacol1985 Oct 01; 28 AB - One-electron oxidation of several derivatives of pyrazolin-5-one, including the drug antipyrine, were studied by pulse radiolysis of aqueous solutions. All the compounds were found to be oxidized by Br2 rapidly (k approximately 3 X 10(8)-2 X 10(9) M-1 s-1) but considerably more slowly by weaker oxidants, such as peroxyl radicals. From redox equilibria using p-methoxyphenol and N,N,N',N'-tetramethyl-p-phenylenediamine as reference compounds, the one-electron oxidation potentials of the methyl-substituted 2-pyrazolin-5-ones were found to be in the range of 0.32-0.39 V versus normal hydrogen electrode. The relevance of these findings to the properties of the drug nafazatrom is discussed. Antipyrine was found to have a much higher oxidation potential, estimated as 1.2-1.5 V, which is rationalized on the basis of the phenyl substitution and lack of resonance stabilization of the radical cation.