Oxidation potentials of phenols and anilines: correlation analysis of electrochemical and theoretical values
Oxidation potentials of phenols and anilines: correlation analysis of electrochemical and theoretical values
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DOI：
10.1039/c6em00694a
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发表时间：
2017-03-01
影响因子：
5.5
通讯作者：
Tratnyek, Paul G.
中科院分区：
文献类型：
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作者：
Pavitt, Ania S.;Bylaska, Eric J.;Tratnyek, Paul G.
苯酚和苯胺作为环境氧化剂（如二氧化锰）的还原剂和被环境氧化剂（臭氧、三重有机物等）转化的还原剂（如模式污染物）已被广泛研究。这些反应的热力学和动力学已经用取代酚和苯胺的氧化势来解释，通常使用的是质量不确定的遗留实验数据集。虽然有许多可供选择的氧化电位数据，但对不同方法获得的数据的相关性、可靠性和一致性的系统分析很少。我们通过对锰氧化苯酚或苯胺的动力学数据进行广泛的相关性分析（从多个来源编译），并从(i)使用循环伏安法和方波伏安法的电化学测量和（ii）使用密度泛函理论的理论计算中获得氧化电位。来自不同来源和实验条件的测量峰电位（E-p）相关性非常强，均方根误差（RMSE）最小，斜率接近1，截距表明50-150 mV的绝对差异一致；然而，不同来源和理论条件下的单电子氧化电位（E1）与实测氧化电位相比，显示出较大的RMSE、斜率和截距。将计算的E1数据与测量的Ep数据进行校准，可以得到精度更高的E1校正值。对于二氧化锰的氧化，将速率常数归一化（到4-氯同系物）可以将来自多个来源的苯酚和苯胺数据进行关联，从而给出一个统一的定量构效关系（QSAR）。这些qsar之间的比较说明了响应和描述变量的观测与机制特征匹配的原则。
Phenols and anilines have been studied extensively as reductants of environmental oxidants (such as manganese dioxide) and as reductates (e.g., model contaminants) that are transformed by environmental oxidants (ozone, triple organic matter, etc.). The thermodynamics and kinetics of these reactions have been interpreted using oxidation potentials for substituted phenols and anilines, often using a legacy experimental dataset that is of uncertain quality. Although there are many alternative oxidation potential data, there has been little systematic analysis of the relevance, reliability, and consistency of the data obtained by different methods. We have done this through an extensive correlation analysis of kinetic data for phenol or aniline oxidation by manganese oxide-compiled from multiple sources-and oxidation potentials obtained from (i) electrochemical measurements using cyclic and square wave voltammetry and (ii) theoretical calculations using density functional theory. Measured peak potentials (E-p) from different sources and experimental conditions correlate very strongly, with minimal root mean squared error (RMSE), slopes approximate to 1, and intercepts indicative of consistent absolute differences of 50-150 mV; whereas, one-electron oxidation potentials (E1) from different sources and theoretical conditions exhibit large RMSE, slopes, and intercepts vs. measured oxidation potentials. Calibration of calculated E1 data vs. measured Ep data gave corrected values of E1 with improved accuracy. For oxidation by manganese dioxide, normalization of rate constants (to the 4-chloro congener) allowed correlation of phenol and aniline data from multiple sources to give one, unified quantitative structure-activity relationship ( QSAR). Comparison among these QSARs illustrates the principle of matching the observational vs. mechanistic character of the response and descriptor variables.