钴(Ⅲ)络合物氧化对苯二胺类化合物的动力学与机理的研究

本文通过监测氧化中间体半醌(S~+)的吸光度变化跟踪反应进程。用初始速率法处理得到了HAc-NaAc介质中Fe(CN)_6~(3-)(Ox′)催化[CO~Ⅲ(NH_3)_5Cl]~(2+)(Ox)氧化CD-4遵循下列动力学方程: d[S~+]/dt=k_(obs).[Ox′]~(0.90)[Ox]~(0.85)认为Fe(CN)_6~(3-)的再生过程是整个反应的决速步骤。估算了决速步的速率常数k(298K)、活化焓△H~(0≠)和活化熵分别为1.92dm~3·mol~(-1)s~(-1)、23.1kcal/mol和20.5cal/mol.K。以TEPPD代替CD-4、以Fe(CN)_6~(4-)代替Fe(CN)_6~(3-)的实验结果支持了所提出的再生机理的合理性。 实验也得到了[Co~Ⅲen_2Cl_2]~+直接氧化CD-4或TEPPD的动力学方程。测定了反应的活化能。认为PPD氧化为半醌是反应的决速步骤。[Co~Ⅲ(NH_3)_6]~(3+)、[Co~Ⅲ(NH_3)_5Cl]~(2+),[CoⅢen_3]~(3+)、[CoⅢen_2Cl_2]~+氧化PPD的实验结果表明,钴(Ⅲ)络合物的取代活性增加,氧化活性亦增加。

THE KINETICS AND MECHANISM OF OXIDATION OF P-PHENYLENE-DIAMINES WITH Co(Ⅲ)-COMPLEXES

The oxidation of CD-4 with[Co111(NH3)5Cl]2+(Ox) catalyzed by Fe(CN)63- (Ox') was investigated in HAc-NaAc buffer solution by means of initial rate method. The empirical rate equation is:The regeneration of Fe(CN)63- is regarded as the rate-determing step. The rate cons" tant(298K) and activation parameters have been evaluated. The results obtained with TEPPD instead of CD-4 or Fe(CN)64- instead of Fe(CN)63- suport the suggested regeneration mechanism.The empirical rate equation of direct oxidation of CD-4 or TEPPD with [Co111 en2Cl2]+ has been formulated. The activation energy was measured. The rate-determing step may be the oxidation of PPD to S+.The experimental results of oxidation of PPD with [Co111(NH3)6]3+ [Co111en3]3+; [Co111(NH3)5C1]2+and [Co111en.Cl2]+ showed that the oxidizing ability of the Co(III)-complexes decreases with their substitution inertness.