Picosecond Dynamics of Organic Ionic Intermediates

将使用皮秒激光闪光光解系统研究快速电子转移反应的机理和后果，该系统旨在记录几皮秒量级的瞬时中间体的吸收。将研究的环加成反应包括：(1)二苯乙烯与烯烃的加成反应；(2)二苯甲酮与多种烯烃和部分炔烃的Paterno-Buchi反应；(3)金属氢化物对芳基酮的光还原反应机理的评价。所有要研究的反应都涉及通过短寿命中间体进行的环加成反应。在这些反应中发生的电子转移过程的背景下，接触离子对和溶剂分离离子对之间的关键区别将第一次被清楚地描绘出来。有机动力学项目授予科罗拉多大学教授凯文·彼得斯的这笔资金将涉及对非常快的化学反应的研究，这些反应在不到十亿分之一秒的时间内完成。被称为环加成反应的反应是通过电子从一个分子到另一个分子的转移和重新分配来促进的，它将由一个激光系统来监测，该系统能够记录只存在几万亿秒的短暂中间物种的存在。了解这些瞬变物种的性质对于确定电子转移在生物和技术过程中各种重要反应中的作用至关重要。

The mechanism and consequences of rapid electron transfer reactions will be investigated using a picosecond laser flash photolysis system designed to record the absorption of transient intermediates on the order of a few picoseconds. The cycloaddition reactions to be investigated include: (1) the addition of olefins to stilbene; (2) the Paterno-Buchi reaction between benzophenone and a variety of alkenes and selected alkynes; and (3) an evaluation of the mechanism for photoreduction of aryl ketones with metal hydrides. All of the reactions to be investigated involve cycloaddition reactions which proceed via short lived intermediates. In the context of the electron transfer processes which occur in these reactions, the crucial differences between contact and solvent separated ion-pairs will be clearly delineated for the first time. %%% This grant from the Organic Dynamics Program to Professor Kevin Peters at the University of Colorado will involve the study of very fast chemical reactions which are complete in less than a billionth of a second. Reactions called cycloadditions, which are promoted by the transfer and redistribution of electrons from one molecule to another, will be monitored by a laser system capable of recording the existence of short-lived intermediate species which only exist for a few trillionths of a second. The need to understand the properties of these transient species is critical to defining the role of electron transfer in a variety of reactions of importance in biological and technological processes.