Spectroscopy and Thermochemistry of Biradicals

将对气相中各种双自由基的生成热进行研究。这项研究将涉及使用激光光致电离质谱学和光电子能谱来测试双自由基形成的价键理论，通过估计单-三重态能隙。所提出的研究是基于这样的假设，即单重态-三重态能隙可以直接从双自由基和母体自由基中间体的电离势中获得。要研究的物种包括苯炔、脱氢甲苯、环炔和其他各种应变分子。适当的前驱体通过超音速喷射闪速热解在气相中生成反应物种，并用真空-紫外激光光电子能谱和质谱仪进行研究。这笔来自有机动力学项目的资金支持哈佛大学陈彼得教授的工作。将进行的调查将包括测量气相中分子的化学反应活性，并将提供信息，使科学家能够预测几个重要类别的化学反应的方向。要研究的化学物种将通过一种名为超音速喷射闪速热解的技术来制备，该技术通过在短时间内将适当的前体暴露在非常高的温度下来产生活性物种。随后用激光光电子能谱和质量分析对生成的物种进行了表征。这项工作对研究大气中产生的物种的反应性具有深远的意义，从而有助于我们理解影响和改变环境的过程。

An investigation of the heats of formation of a variety of biradicals will be conducted in the gas phase. The study will involve the use of laser photoionization mass spectroscopy and photoelectron spectroscopy to test the valence bond theory for biradical formation by making estimates of the singlet-triplet gap. The proposed investigation is based upon the assumption that the singlet-triplet energy gap can be obtained directly from the ionization potentials of the biradical and the parent radical intermediates. Species to be studied include benzynes, dehydrotoluenes, cycloalkynes, and a variety of other strained molecules. The reactive species will be generated in the gas phase by supersonic jet flash pyrolysis of appropriate precursors, and studied by vacuum-uv laser photoelectron and mass spectroscopy. %%% This grant from the Organic Dynamics Program supports the work of Professor Peter Chen at Harvard University. The investigation to be conducted will involve measurements of the chemical reactivity of molecules in the gas phase, and will provide information which will allow scientists to predict the direction of several important classes of chemical reactions. The chemical species to be investigated will be prepared by a technique called super-sonic jet flash pyrolysis, which results in the generation of reactive species by exposure of appropriate precursors to very high temperatures in a short time frame. The species produced are subsequently characterized by laser photoelectron spectroscopy and mass analysis. This work has profound implications for investigation of the reactivity of species which are produced in the atmosphere, and thus contributes to our understanding of processes which effect and alter the environment.