Chemistry of Carbanions

这项有机和大分子化学项目资助了加州大学伯克利分校的Andrew Streitwieser教授的实验和理论研究，旨在分析碳的化学结构和反应性。碳离子是带负电荷的有机分子片段，如碳氢化合物，在实验室、体内和工业化学过程中的各种化学反应中作为瞬态中间体出现。因此，可以说，碳的化学反应性决定了许多化学变化的路径。Streitwieser博士的研究将包括通过研究氢同位素交换速率来测量弱碳酸的动态酸度，包括氢氧化钠水溶液中的苯和环己胺中锂和铯环己胺环己胺中的环碳氢化合物。平衡酸度的研究将继续进行，特别是对阴离子和在四氢呋喃中不稳定的碳离子的研究。后者的例子包括五氟苯和其他卤化碳氢化合物。在观察到芳基乙酸的低秒pKa后，将进行浓度效应的测量，以分析单盐和二盐的聚集效应。理论工作将集中在从头计算碳离子及其锂和钠盐的电子结构和几何形状。计算还将用于估计碳离子反应的过渡结构，特别强调前面提到的系统，以及金属化腙，肟和亚胺，其重要的立体化学性质尚未得到很好的理解。

This grant in the Organic and Macromolecular Chemistry Program supports experimental and theoretical research by Prof. Andrew Streitwieser, University of California at Berkeley, aimed at analyzing the chemical structure and reactivity of carbanions. Carbanions are negatively charged fragments of organic molecules such as hydrocarbons and occur as transient intermediates during a wide variety of chemical reactions in the laboratory, in the body, and in industrial chemical processes. Thus, the chemical reactivity of carbanions may be said to determine the path of many chemical changes. Dr. Streitwieser's research will include measurements of kinetic acidities of weak carbon acids by the study of hydrogen isotope exchange rates, including benzene in aqueous sodium hydroxide and cyclic hydrocarbons with lithium and cesium cyclohexylamide in cyclohexylamine. Equilibrium acidity studies will be continued, particularly for dianions and for carbanions not stable in THF. Examples of the latter include pentafluorobenzene and other halogenated hydrocarbons. Following observations of low second pKa's for arylacetic acids, measurements of concentration effects will be made to analyze effects of aggregation of both mono- and di-salts. Theoretical work will focus on ab initio computations of electronic structures and geometries of carbanions and their lithium and sodium salts. Calculations will also be used to estimate the transition structures of carbanion reactions, with particular emphasis on the previously noted systems, and on metallated hydrazones, oximes, and imines whose important stereochemical properties are not yet well understood.