Fe(III)与2,3-二羟基苯甲酸配位反应的动力学和机理

研究了水溶液中三价铁与2,3-二羟基苯甲酸络合反应的机理与动力学. 测定并计算了络合作用的反应速度常数. 活性 和活性焓随氢离子浓度增加而降低, 指明了FeCH2(3+)的缔合机理和FeOH(2+)与Fe2(OH)2(4+)的解离活化机理, 反应速率方程表明氢离子浓度的依赖关系对Fe(III)络合作用是典型的. 但是在[Fe(III)]的二级反应动力学则有一个反常贡献.

Kinetics and mechanism of the complexing of Fe(III) by 2,3-dihydroxybenzoic acid

The kinetics and mechanism for complexing of aqueous Fe(III) by 2,3-dihydroxybenzoic acid (I) were studied in 1.00 mol.dm-3 ionic strength with [H+]1.00 ?10-2 to 0.700 mol.dm-3, and [Fe(III)]/[I] ?10. The rate constants for complexing of FeOH23+, FeOH2+ and Fe2(OH)4+ by I were measured and calculated The activation enthalpy and entropy decrease with increasing [H+]. This indicates an associative mechanism for FeOH23+ and a dissociative mechanism for FeOH2+ and Fe2(OH)24+. The reaction rate equation shows the H+ dependence typical for Fe(III) complexation, but there is an unusual contribution from a kinetic term 2nd order in [Fe(III)]. A possible mechanism is proposed.