物理化学学报 >> 2004, Vol. 20 >> Issue (08): 801-805.doi: 10.3866/PKU.WHXB20040804

研究论文 上一篇    下一篇

铱(III)离子催化铈(IV)离子氧化异丁醇的反应动力学及机理

宋文玉;李红变;刘红梅   

  1. 河北大学化学与环境科学学院,保定 071002
  • 收稿日期:2004-01-05 修回日期:2004-03-15 发布日期:2004-08-15
  • 通讯作者: 宋文玉 E-mail:songwenyu@126.com

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

Song Wen-Yu;Li Hong-Bian;Liu Hong-Mei   

  1. College of Chemistry and Environmental Science, Hebei University, Baoding 071002
  • Received:2004-01-05 Revised:2004-03-15 Published:2004-08-15
  • Contact: Song Wen-Yu E-mail:songwenyu@126.com

摘要: 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25~40 ℃区间氧化异丁醇(BA)的反应动力学.结果表明反应对铈(IV)离子为一级,对异丁醇的表观反应级数为正分数.准一级速率常数kobs随[H+]及催化剂[Ir(Ⅲ)]增加而增大,随[HSO4-]增加而减小.在氮气保护下,反应不能引发丙烯酰胺聚合,说明在反应中没有自由基产生.提出了催化剂、底物和氧化剂间生成双核加合物的反应机理,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.

关键词: 铱(III)离子, 铈(IV)离子, 异丁醇, 催化剂, 动力学及机理

Abstract: The kinetics of iridium(III) catalyzed oxidation of isobutyl alcohol by cerium(III) in aqueous sulphuric acid medium has been investigated by titrimetric technique in the temperature range of 25~40 ℃.The reaction order of [Ce(IV)] was found to be unity and that in isobutyl alcohol to be positive fractional. It was found that the pseudo first order ([(CH3)2CHCH2OH] >> [Ce(IV)]) rate constants kobs increases with the increase of [Ir(III)] and [H+],but decreases with the increase of [HSO4-].Under the protection of nitrogen the reaction system does not induce polymerization of acrylamide indicating no generation of free radicals. Formatoin of a dinuclear complex involving the oxidant, catalyst and the substrate before the rate-determining step has been proposed in the reaction mechanism, and the rate equation derived from the mechanism can explain all experimental observations. From the hydrogensulphate dependence, Ce(SO4)2+ has been found as the kinetically active species. The pre-equilibrium constants, rate constants of the rate-determining step together with the parameters were evaluated.

Key words: Iridium(III) ion, Cerium(IV) ion, Isobutyl alcohol, Catalyst, Kinetics and mechanism