碱性介质中二(高碘酸根)合铜(Ⅲ)酸根氧化乙二醇独丁醚的反应动力学及机理

在25℃～40℃区间用分光光度法在碱性介质中研究了二(高碘酸根)合铜(Ⅲ)酸根配离子(DPC)氧化乙二醇独丁醚(EGB)的反应动力学。结果表明:反应对DPC为一级,对EGB是1< n_ap< 2(n_ap代表表观反应级数);在保持准一级条件(EGB]₀ 》Cu(Ⅲ)]₀)下,表观速率常数,k_obs,在弱碱性介质中,随OH^-]增大而减小,在较强碱性介质中随OH^-]增大而增大,随着IO₄^-]增加而减小;无盐效应。提出了含有自由基过程的反应机理,由假设的两种同时进行的反应机理推出的速率方程能很好的解释全部实验现象,进一步求得速控步的速率常数和活化参数。

Kinetics and Mechanism of Oxidation of Ethylene Glycol Monobutyl Ether by Diperiodatocuprate(Ⅲ) in Alkaline Medium

Copper (Ⅲ) has received extensive attention recently because of its apparent involvement in various biological processes. Amounts of work have been reported. But because Cu (Ⅲ) is in the highest oxidation state and the reaction is complicated in this system, it is of significance to have a further study on this kind of reaction system.Investigation on them will certainly provide us with more dynamical parameters, and will provide theoretical foundation for the reaction route design of the organic synthesis and quantitative analysis of analytical chemistry.The kinetics of oxidation of ethylene glycol monobutyl ether (EGB) by diperiodatocuprate (Ⅲ) complex (DPC)was studied spectrophotometrically between 25℃ and 40℃ in alkaline medium. All kinetic measurements werecarried out under pseudo-first order conditions. The reaction process was monitored automatically by recording the varying curve of absorbance (A) of reaction solution with time (t) at 415nm with a spectrometer.The reaction rate showed first order dependence in DPC and 1 ＜ nap ＜ 2 in EGB. It was found that under the conditions of the pseudo-first order (EGB] 0 >Cu (Ⅲ)]0), the rate constant, kobs, changed differently under different OH-] . At low OH-], kobs decreased with increase in OH-], but when OH-] increased to enough extent, kobs increased with increase in OH- ], and then it decreased with increase in IO4- ]. There is no effect of addition of salt like KNO3. Free radicals were observed in the process of reaction. A plausible mechanism involving free radical was proposed. The rate equations derived from two simultaneous mechanisms can explain all experimental observations. The activation parameters along with the rate constants of the rate-determining step were calculated.