An in situ UV-vis spectroelectrochemical investigation of the initial stages in the electrooxidation of selected ring- and nitrogen-alkylsubstituted anilines
An in situ UV-vis spectroelectrochemical investigation of the initial stages in the electrooxidation of selected ring- and nitrogen-alkylsubstituted anilines
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DOI：
10.1016/s0013-4686(98)00390-9
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发表时间：
1999-01-01
影响因子：
6.6
通讯作者：
Holze, R
中科院分区：
文献类型：
--
作者：
Malinauskas, A;Holze, R
采用原位紫外-可见光谱电化学技术，研究了几种N-烷基取代（N-乙基-和N，N-二甲基-）和环取代（o-、m-、对甲基、o-乙基-）苯胺衍生物在ITO玻璃电极上的电氧化反应。用n -乙基苯胺，在阳极电位步骤后观察到中间产物和最终产物的明确吸光度峰。演示了电生成的中间体转化为最终产品的过程。观察了N，N-二甲基苯胺电生成中间体的形成及其电解中断后的消耗。然而。没有检测到最终产物。这被解释为C-C（尾对尾）耦合，导致在所研究的光谱范围内无法检测到的联苯胺型最终产物。在λ = 450 nm处检测到环烷基取代苯胺的吸光度瞬态，显示出典型的中间物质的时间依赖行为。在λ = 750 nm处的吸光度瞬变是由环取代苯胺电氧化的最终产物引起的。根据所得结果，提出了反应顺序。在足够高的阳极电位下，所有被研究的苯胺衍生物都发生电氧化，生成中间体。在接下来的化学步骤中，中间体与底物的溶液分子发生反应。与未取代苯胺的化学反应进行得最快，而环烷基取代衍生物的反应稍慢。n -烷基取代苯胺衍生物的化学反应最慢。1999爱思唯尔科学有限公司版权所有。
The electrooxidation of a selection of N-alkylsubstituted (N-ethyl- and N,N-dimethyl-) and ring-substituted (o-, m-, p-methyl-, o-ethyl-) aniline derivatives at ITO glass electrodes was investigated in acidic solutions with in situ UV-vis spectroelectrochemistry. With N-ethylaniline well defined absorbance peaks of an intermediate and of an end product were observed after an anodic potential step. The conversion of the electrogenerated intermediate into an end product was demonstrated. With N,N-dimethylaniline the formation of an electrogenerated intermediate as well as its consumption after interruption of electrolysis were observed. However. no end product was detected. This is interpreted in terms of a C-C (tail-to-tail) coupling, leading to a benzidine type end product which is not detectable in the investigated spectral range. Absorbance transients were detected at lambda = 450 nm for ring-alkylsubstituted anilines, showing the typical time dependent behaviour of an intermediate species. Absorbance transients at lambda = 750 nm were identified as being caused by end products of the electrooxidation of ring-substituted anilines.A reaction sequence is proposed based on the results obtained. At sufficiently high anodic potentials all investigated aniline derivatives undergo electrooxidation, yielding intermediates. In the following chemical step, intermediates react with solution phase molecules of the substrate. The fastest chemical reaction proceeds with unsubstituted aniline, whereas ring-alkylsubstituted derivatives react somewhat slower. The slowest chemical reaction proceeds with N-alkylsubstituted aniline derivatives. (C) 1999 Elsevier Science Ltd. All rights reserved.