Organic Free Radical and Electron Transfer Chemistry

有机动力学项目的这笔赠款代表了德克萨斯农工大学马丁·纽科姆的工作的继续。这个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。这项工作意义重大，因为它将调查许多被怀疑通过被称为SET(单电子转移)的途径进行的反应，这些反应以前被认为是通过其他机制进行的。这将加强对有机反应如何进行的了解，从而提高对如何改进它们的了解。将继续研究有机自由基领域和有机反应中潜在电子转移过程的机制。极快的碳自由基重排动力学将由德克萨斯A&M实验室开发的PTOC/硫醇方法研究，目的是快速校准自由基时钟，以便它们可以在非粘性溶剂中与扩散控制的二级过程竞争。在PTOC/硫醇法中，以N-羟基吡啶-2-硫酮酯为自由基前驱体，以硫酚为自由基捕捉剂，可在25℃下校正一级速率常数大于1×10~(-9)/S的反应。N-羟基吡啶-2-硫酮氨基甲酸酯的氨基和氨基也将被研究。主要目标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，将校准以氮为中心的自由基时钟。潜在的电子转移过程(特别是在二烷基胺锂反应中)将继续被研究。将寻求对二烷胺阴离子-二烷胺自由基对的实验得出的氧化电位进行验证。将研究二烷基胺锂与三丁基卤化物的反应；最近的结果表明，在这种情况下，以前没有考虑过的反应过程可能正在进行。

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.