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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >S-Oxygenation of Thiocarbamides.3.Nonlinear Kinetics in the Oxidation of Trimethylthiourea by Acidic Bromate
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S-Oxygenation of Thiocarbamides.3.Nonlinear Kinetics in the Oxidation of Trimethylthiourea by Acidic Bromate

机译：硫脲的S-氧合反应。3。酸性溴酸盐氧化三甲硫脲的非线性动力学

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摘要

The oxidation of trimethylthiourea(TMTU)by acidic bromate has been studied.The reaction mimics the dynamics observed in the oxidation of unsubstituted thiourea by bromate with an induction period before formation of bromine.The stoichiometry of the reaction was determined to be 4:3,thus 4BrO_3~-+3R1R2C=S+3H2O->4Br~-+3R1R2C=O+3SO_4~(2-)+6H~+.This substituted thiourea is oxidized at a much faster rate than the unsubstituted thiourea.The oxidation mechanism of TMTU involves initial oxidations through sulfenic and sulfinic acids.At the sulfinic acid stage,the major oxidation pathway is through the cleavage of the C-S bond to form a reducing sulfur leaving group,which is easily oxidized to sulfate.The minor pathway through the sulfonic acid produces a very stable intermediate that is oxidized only very slowly to urea and sulfate.The direct reaction of aqueous bromine with TMTU was faster than reactions that form bromine,with a bimolecular rate constant of(1.50±0.04)X10~2 M~(-1)s~(-1).This rapid reaction ensured that no oligooscillatory bromine formation was observed.The oxidation of TMTU was modeled by a simple reaction scheme containing 20 reactions.
机译：研究了酸性溴酸盐对三甲基硫脲（TMTU）的氧化作用，该反应模拟了在溴形成前的诱导期，溴酸盐对未取代的硫脲进行氧化的动力学，反应的化学计量确定为4：3，因此4BrO_3〜-+ 3R1R2C = S + 3H2O-> 4Br〜-+ 3R1R2C = O + 3SO_4〜（2-）+ 6H〜+。该取代的硫脲的氧化速度比未取代的硫脲快得多。 TMTU涉及通过亚硫酸和亚磺酸的初始氧化。在亚磺酸阶段，主要的氧化途径是通过CS键的裂解形成还原性硫离去基团，该基团容易被氧化成硫酸盐。次要途径是通过磺酸生成一个非常稳定的中间体，该中间体仅被非常缓慢地氧化为尿素和硫酸盐。溴水溶液与TMTU的直接反应比形成溴的反应要快，双分子速率常数为（1.50±0.04）X10〜2 M〜（- 1）s〜（-1）。通过简单的反应方案（包含20个反应）来模拟TMTU的氧化。

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