Organic Free Radical and Electron Transfer Chemistry

这项有机动力学项目的拨款代表了德克萨斯农工大学马丁·纽科姆工作的延续。本项目的目的是阐明涉及自由基或自由基阴离子的有机反应的途径。这项工作非常重要，因为它将研究许多被怀疑通过称为SET（单电子转移）途径进行的反应，这些反应以前被认为是通过其他机制进行的。这将提高人们对有机反应如何进行的认识，因此，如何改进这些反应。将继续研究有机自由基和有机反应中潜在电子转移过程的机制。德克萨斯a&m实验室开发的PTOC/thiol方法将研究极快碳自由基重排的动力学，目的是校准如此快的自由基时钟，以便它们可以与非粘性溶剂中的扩散控制二阶过程竞争。在PTOC/thiol方法中，n -羟基吡啶-2-硫酮酯作为自由基前体，噻吩作为自由基捕获剂，可以在25℃下校准一级速率常数大于1 × 10ex -9/s的反应。氨基和氨基阳离子自由基从n -羟基吡啶-2-氨基硫酮氨基甲酸酯也将进行研究。主要目的是确定这些中间体的简单二级反应（如氢原子转移）的速率常数；有了基本反应速率常数，氮中心原子钟将被校准。潜在的电子转移过程（特别是在锂二烷基酰胺的反应中）将继续研究。验证实验导出的氧化电位的双氯胺阴离子-二氯胺基自由基对将寻求。研究了二烷基酰胺锂与卤化三烷基的反应；最近的结果表明，在这种情况下，以前未被考虑到的反应过程可能正在起作用。

This grant within the Organic Dynamics Program represents a continuation of the work by Martin Newcomb of Texas A&M University. The aim of this project is to elucidate the pathway of organic reactions which involve free radicals or radical anions. This work is quite significant in that it will investigate many reactions suspected to proceed by the pathway known as SET (single electron transfer) which have previously been considered to react by other mechanisms. This will enhance knowledge about how organic reactions proceed, and, therefore, how they can be improved. Continued studies in the areas of organic free radicals and mechanisms of potential electron transfer processes in organic reactions will be investigated. Kinetics of exceedingly fast carbon radical rearrangemens will be studied by the PTOC/thiol method developed in the Texas A&M laboratory with the objective of calibrating radical clocks so fast that they may be used in competition with diffusion-controlled second order processes in non-viscous solvents. In the PTOC/thiol method, N-hydroxypyridine-2-thione esters are employed as radical precursors and thiophenol is used as a radical trapping agent, and reactions with first order rate constants in excess of 1 x 10exp-9/s at 25 degrees C can be calibrated. Aminyl and aminium cation radicals from N-hydroxpyridine-2-thione carbamates will also be studied. The main objective will be to determine the rate constants for simple second order reactions (such as hydrogen atom transfer) of these intermediates; with basis reaction rate constants available, nitrogen-centered radical clocks will be calibrated. Potential electron transfer processes (especially in reactions of lithium dialkylamides) will continue to be studied. Verification of the experimentally derived oxidation potential for the dialklamide anion--dialkylaminyl radical couple will be sought. Reactions of lithium dialkylamides with trityl halides will be studied; recent results suggest that a previously unconsidered reaction process may be operating in this case.