碱性介质中二羟基二(高碘酸根)合镍(Ⅳ)酸根氧化α-丙二醇的反应动力学及机理

Kinetics and Mechanism of Oxidation of α-Propylene Glycol by Dihydroxydiperiodatonickelate(Ⅳ)in Alkaline Medium

用分光光度法在293.2～308.2K区间研究了碱性介质中二羟基二(高碘酸根)合镍?酸根(DPN)氧化α-丙二醇(α-PG的反应动力学及机理。结果表明:反应对DPN为准一级,对α-PG为正分数级;在保持准一级条件(犤α-PG犦0犤DPN犦0)下,表观速率常数随着犤OH-犦的增加而增大,随着犤IO4-犦的增加而减小;无明显的盐效应。据此提出了包括α-PG和MPN形成络合物的前期平衡的反应机理,由假设反应机理推出的速率方程能很好地解释全部实验现象,进一步求得了速控步的活化参数。

The kinetics of oxidation of α propylene glycol (α PG) by dihydroxydiperiodatonickelate? (DPN) in alkaline medium was studied with spectrophotometry in a temperature range of 293.2～308.2K. The reaction was found to be pseudo first order with respect to DPN and fractional order to α PG. The rate increases with the increase in and decreases with the increase in . Added salts did not affect the rate and no free radical was detected. A mechanism of reaction involving a pre equilibrium of an adduct formation between α PG and dihydroxymonoperiodatonickelate? (MPN) is proposed, which can explain all the experimental results. The activation parameters of the rate determining step have been calculated.