Determination of absolute rate constants for the reversible hydrogen-atom transfer between thiyl radicals and alcohols or ethers
作者:Christian Schöneich、Klaus-Dieter Asmus、Marija Bonifačić
DOI:10.1039/ft9959101923
日期:——
have been determined for the reversible hydrogen-transfer process R˙+ RSH ⇄ RH + RS˙ by pulse radiolysis, mainly through direct observation of the RS˙ radical formation kinetics in water–RH (1 : 1, v/v) mixtures. The thiols investigated were penicillamine and glutathione; the RH hydrogen donors were methanol, ethanol, propan-1-ol, propan-2-ol, ethylene glycol, tetrahydrofuran and 1,4-dioxane with the
已通过脉冲辐解确定了可逆氢转移过程R˙+RSH⇄RH +RS˙的绝对速率常数,主要是通过直接观察水-RH中的RS˙自由基形成动力学来确定的(1:1,v / v)混合物。所研究的硫醇为青霉胺和谷胱甘肽;RH的氢供体为甲醇,乙醇,丙-2-醇,丙-2-醇,乙二醇,四氢呋喃和1,4-二恶烷,其中提取的氢位于羟基或烷氧基官能团的α处。上述平衡的正向反应(在放射生物学中称为“修复”反应)的速率常数通常约为10 7 – 10 8 dm 3 mol –1 s –1而通过硫氢基自由基从RH吸氢(逆过程)的速率常数约为10 3 – 10 4 dm 3 mol –1 s –1。这样产生的平衡常数约为10 4。基于这些数据,标准还原电势可以为R'R来评价“COH / H + // R'R”CHOH,R'R“CO / H + // R'R”C(OH)和R'R“CO //R'R'C˙O -选自甲醇,乙醇和丙-2-醇夫