Nonlinear dynamics in chemistry derived from sulfur chemistry. Part 2. New experimental data on the chlorite-thiourea reaction
Nonlinear dynamics in chemistry derived from sulfur chemistry. Part 2. New experimental data on the chlorite-thiourea reaction
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DOI：
10.1021/j100146a035
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发表时间：
1993-11
期刊：
影响因子：
--
通讯作者：
C. Chinake;R. H. Simoyi
中科院分区：
文献类型：
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作者：
C. Chinake;R. H. Simoyi
图1.在360 nm处的吸收迹线为三甲基溴化铵与（a）AIMSA、（B）AMS A和（c）硫脲的反应。[ClOrlo]= 0.004 M，每种还原剂的初始浓度为0.001 M。反应温度为25 ℃，离子强度为0.5M（NaClO 4）.亚磺酸氧化为亚磺酸的反应速度较慢，双分子速率常数仅为27.8M_1s ~*。二氧化氯的形成与pH值的突然下降和硫酸盐的突然形成相一致，所有这些似乎都表明R10和R11（或任何磺酸氧化成硫酸盐）是快速和不可逆的。我们目前的研究表明，我们在文献2中提出的机制也不能充分描述我们在亚氯酸盐-硫脲反应中观察到的二氧化氯行波。5这可能是因为反应步骤的选择不好或对某些反应步骤的相关动力学参数估计不佳。特别值得注意的是，波前不是尖锐的，但包含在反应区之前的可清楚观察到的反应区。5反应区可用酸碱指示剂观察，但用氯化钡4和淀粉作指示剂时则不能观察。[5]对有限反应区的观察表明，化学波中有一个区域是由化学动力学控制的。这导致人们相信，控制从磺酸形成硫酸盐的相关速率常数可能并不那么高。我们现在已经积累了更多的数据，表明fcio和ku的修订是必要的：（a）氨基亚氨基甲烷亚磺酸，NH 2（NH）CS 02 H（AIMSA），这是一个建议的中间体在硫脲氧化为硫酸盐，与硫脲反应，并观察到相同类型的行为与硫脲本身，时钟反应特性，行波，以及时空行为。8（B）A磺酸，氨基甲磺酸，NH 2CH 2-SO 3 H（AMSA），也与NH3反应，并且反应没有km和kn预测的那么快。图1示出了用硫脲和硫脲、AIMSA和AMSA获得的吸光度迹线。用磺酸获得最长的诱导时间。8（c）Rabai等人最近的工作表明，二氧化氯与硫脲反应产生二硫代双甲脒离子（NH 2）CSSC（NH 2）2+或AIMSA，这取决于二氧化氯与硫脲的初始比例。9磺酸仅在高酸中形成，并且之后产生硫酸盐的反应可以忽略不计。(d)我们做了一些实验，监测还原剂的消耗速度。噻托溴铵具有吸收性，
Figure 1. Absorption traces at 360 nm of the reaction of chlorite with (a) AIMSA,(b) AMS A, and (c) thiourea.[ClOrlo= 0.004 M, and the initial concentration of each of the reductants is 0.001 M. Reaction temperature was 25 C, and the ionic strength was 0.5 M (NaC104). the oxidation of the sulfenyl acid to sulfinic acid, is comparatively slow with a bimolecular rate constant of only 27.8 M_1 s~*. The formation of chlorine dioxide coincides with a sudden decrease in pH and a sudden formation of sulfate, all of which seemed to suggest that R10and Rll (or any oxidationof the sulfonic acid to sulfate) are fast and irreversible. Our present studies show that the mechanism we suggested in ref 2 also cannot adequately describe the traveling wave of chlorine dioxide we observe in the chlorite-thiourea reaction. 5 This could be because of a bad choice of reaction steps or poor estimation of the relevant kinetics parameters of some of the reaction steps. Of particular note is the fact that the wave front is not sharp but contains a clearly observable reaction zone which precedes the reacted zone. 5 The reaction zone can be observed by using an acid-base indicator but cannot be observed when barium chloride4 and starch are used as indicators. 5 The observation of a finite reaction zone suggests a region in the chemical wave that is dominated by chemical kinetics. This leads to the belief that the relevant rateconstants that control the formation of sulfate from sulfonic acid may not be that high. We have now accumulated more data that suggest that a revision of fcio and ku is necessary:(a) The aminoiminomethanesulfinic acid, NH2 (NH) CS02H (AIMSA), which is one of the proposed intermediates in the oxidation of thiourea to sulfate, was reacted with chlorite, and the same type of behavior was observed as with thiourea itself, clock reaction characteristics, traveling waves, as well as spa-tiotemporal behavior. 8 (b) A sulfonic acid, aminomethanesulfonic acid, NH2CH2-S03H (AMSA), was also reacted with chlorite, and the reaction was not as fast as predicted by km and kn. Figure 1 shows the absorbance traces obtained with chlorite and thiourea, AIMSA, and AMSA. The longest induction time was obtained with the sulfonic acid. 8 (c) Recent work by Rabai et al. have shown that the reaction of chlorine dioxide with thiourea yields dithiobisformamidine ion,(NH2) CSSC (NH2) 2+, or AIMSA, depending on initial ratio of chlorine dioxide to thiourea. 9 The sulfonic acid is formed only in high acid, and there is negligible reaction after that to give sulfate.(d) We have run some experiments in which we monitor the rate of consumption of the reductants. Thiourea has an absorption