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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >A Novel Approach for Measuring Absolute Rate Constants by Pulsed Electron Spin Resonance: Addition of Phosphinoyl and 2-Hydroxy-2-propyl Radicals to Several Alkenes
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A Novel Approach for Measuring Absolute Rate Constants by Pulsed Electron Spin Resonance: Addition of Phosphinoyl and 2-Hydroxy-2-propyl Radicals to Several Alkenes

机译：一种通过脉冲电子自旋共振测量绝对速率常数的新方法：将膦酰基和2-羟基-2-丙基自由基加到几个烯烃上

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摘要

A time-resolved Fourier transform electron spin resonance (TR FT ESR) method for determining absolute rate constants of reactive, free radical reactions is described. The phase memory times T_M of a family of reacting radicals were measured precisely by electron spin-echo (ESE) detection. In all cases the ESE signal decays show a simple pseudo-first-order behavior. Rate constants of the reactions were extracted from the linear relationship between the reciprocal of the T_M values and the alkene concentrations. The validity of the method is demonstrated for the measurement of the rate constant for addition of different phosphinoyl and 2-hydroxy-2-propyl radicals to several acrylates, methyl methacrylate, and vinyl pivalate in organic solvents at room temperature. The results are in excellent agreement with those obtained by other kinetic investigations employing time-resolved steady-state electron spin resonance (TR CW ESR) and optical absorption spectroscopy. The technique is shown to be applicable to systems with rate constants between 10~4 and 10~8 M~(-1) s~(-1), a range covered by the alkenes examined.
机译：描述了确定反应性自由基反应的绝对速率常数的时间分辨傅里叶变换电子自旋共振（TR FT ESR）方法。通过电子自旋回波（ESE）检测可精确测量一系列反应自由基的相存储时间T_M。在所有情况下，ESE信号衰减都显示出简单的伪一阶行为。从T_M值的倒数与烯烃浓度之间的线性关系中提取反应的速率常数。证明了该方法的有效性，用于测量室温下在有机溶剂中向几种丙烯酸酯，甲基丙烯酸甲酯和新戊酸乙烯酯中添加不同膦酰基和2-羟基-2-丙基的速率常数。该结果与采用时间分辨稳态电子自旋共振（TR CW ESR）和光吸收光谱法进行的其他动力学研究获得的结果非常一致。结果表明该技术适用于速率常数在10〜4和10〜8 M〜（-1）s〜（-1）之间的系统，该范围被所考察的烯烃覆盖。

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