铱(III)离子催化铈(IV)离子氧化四氢糠醇的动力学及机理

在酸性介质中用氧化还原滴定法研究了铈(IV)离子在痕量铱(III)离子催化作用下，于298~313 K区间氧化四氢糠醇(THFA)的反应动力学. 结果表明，反应对铈(IV)离子为一级，对铱(III)离子也为一级，对四氢糠醇的表观反应级数为正分数. 准一级速率常数kobs随H+]增加而增大，而随HSO₄－]增加而减小. 在氮气保护下，反应能引发丙烯腈聚合，说明在反应中有自由基产生. 通过kobs与HSO₄－]的依赖关系，找到本反应体系的动力学活性物种是Ce(SO₄)₂，并计算出平衡常数，速控步骤的速率常数及相应的活化参数.

Kinetics and Mechanism of Iridium(Ⅲ) Catalyzed Oxidation of Tetrahydrofurfuryl Alcohol by Cerium(Ⅳ) in Aqueous Sulphuric Acid Medium

The kinetics of trace Ir(III) catalyzed oxidation of tetrahydrofurfuryl alcohol(THFA) by Ce(IV) in aqueous sulphuric acid medium was studied by titrimetric technique of redox in the temperature range of 298~313 K. The order was found to be unity with respect to both Ce(IV) and Ir(III), and for tetrahydrofurfuryl alcohol the apparent reaction order was a positive fraction. It was found that the pseudo first order (THFA]>>Ce(IV)]) rate constant, kobs, increased with the increase of H＋] but decreased with the increase of HSO₄－]. Under the protection of nitrogen, however, the reaction system could induce polymerization of acrylonitrile, indicating the generation of free radicals. A reasonable mechanism involving a preequilibrium was proposed. From the relation between kobs and HSO₄－], Ce(SO₄)₂ was found to be the kinetically active species. The equilibrium constants and rate constants of the rate-determining step along with the activation parameters were evaluated.