Study of Reactive Intermediates Using Photoacoustic Calorimetry (Chemistry)

这项有机和大分子化学项目的拨款支持Joshua Goodman教授的研究，该研究旨在开发一种被称为脉冲时间分辨光声量热法（PAC）的实验技术，并将其应用于解决有机化学和光化学中的几个重要问题。这项工作很重要，因为PAC技术能够同时测量溶液中光诱导反应的动力学和能量。光化学反应是既具有基础意义又具有实际意义的过程，因此了解这些反应中逐步发生的结构和能量变化是一个重要的目标。Goodman博士的工作有三个主要目标：(1)通过将PAC技术扩展到非均匀介质，并将时间分辨率提高到50纳秒，从而继续发展PAC技术；(2)利用PAC技术测量重要化学体系中的键离解能，如1,4-双自由基、俘获自由基和阳离子自由基；(3)测定环丙烷异构化过程中非光谱反应中间体的反应活性和能量学。这些新的测量是可能的，因为光声技术可以时间分辨活性中间体的非辐射衰变过程，如发生在光化学反应中的那些。

This grant in the Organic and Macromolecular Chemistry Program supports research by Prof. Joshua Goodman, which is aimed at the development of an experimental technique known as pulsed time-resolved photoacoustic calorimetry (PAC) and applying it to the solution of several important problems in organic chemistry and photochemistry. This work is important because the PAC technique is capable of simultaneously measuring both dynamics and energies of light-induced reactions in solution. Photochemical reactions are processes of both fundamental and practical interest, so understanding the step-by-step structural and energetic changes involved in these reactions is an important goal. Dr. Goodman's work has three principal objectives: (1) to continue development of the PAC technique by extension to non- homogeneous media and by improvement of time resolution to the 50-nanosecond regime; (2) to employ PAC techniques to measure bond dissociation energies in important chemical systems such as 1,4-biradicals, captodative radicals, and cation radicals; and (3) to determine the reactivity and energetics of non- spectroscopic reactive intermediates in cyclopropane isomerizations. These novel measurements are possible because the photoacoustic technique can time-resolve the non-radiative decay processes of reactive intermediates such as those occurring in photochemical reactions.