Elementary Steps Associated with Addition and Elimination Reactions

有机和大分子化学项目支持博士的研究。他们的目标是对那些影响1,2消去反应的电子因素进行实验研究。碱诱导氢和相邻碳的离去基(x)的消去是一个非常复杂的过程，与生物化学和工业化学都有关系。HX跨双键加成的逆向过程也是有机化学中的主要反应，了解其各种机理是一个值得研究的重要课题。更具体地说，将研究碳和氧之间的质子转移反应，并将其与醇醇溶液中产生的碳离子中间体的卤化物喷射反应进行比较。饱和卤代烷与醇氧的反应导致质子从碳转移到氧，形成与-卤化物成氢键的碳离子。阴离子可以通过失去-卤化物形成烯烃或将质子转移回碳（内部返回）来中和。后者是一个不发生反应的过程，但它可以通过研究氢与消除反应相关的初级动力学同位素效应来检测。第三个反应会产生新的碳离子，它没有接触稳定。如果该阴离子在卤化物损失之前被中和，则可以使用氘化醇作为溶剂来检测该过程。还将测量与消除有关的α和β碳同位素效应。氟卤烯烃与醇氧化合物反应直接生成游离碳离子。如果反应发生在醇中，则卤化物的损失或质子化之间存在竞争以中和阴离子。将比较两种方法产生的碳的化学性质。

The Organic and Macromolecular Chemistry Program supports the research of Drs. Heinz and Judith Koch, which aims at an experimental study of those electronic factors that influence 1,2-elimination reactions. The base induced elimination of a hydrogen and a leaving group (x) from an adjacent carbon is a very complicated process that has relevance to both biological and industrial chemistry. The reverse process, the addition of HX across a double bond is also a major reaction in organic chemistry and an understanding of its various mechanisms is an important topic worthy of study. More specifically, proton-transfer reactions between carbon and oxygen will be studied and compared to ejection of halide from carbanion intermediates that are generated in alcoholic alkoxide solutions. Reactions of saturated haloalkanes with alkoxide result in proton transfer from carbon to oxygen to form a hydrogen-bonded carbanion with a beta-halide. The anion can be neutralized by either a loss of the beta-halide to form an alkene, or transfer of the proton back to carbon (internal return). The latter is a no-reaction process, but it can be detected by the study of primary kinetic isotope effects of hydrogen associated with the elimination reaction. A third reaction would lead to a new carbanion that is free of contact stabilization. If that anion is neutralized prior to halide loss, the process can be detected by using a deuterated alcohol as solvent. Both alpha and beta-carbon isotope effects associated with the eliminations will also be measured. Reactions of fluorohaloalkenes with alkoxide generate a free carbanion directly. If reaction occurs in alcohol there is a competition between loss of halide or protonation to neutralize the anion. Chemistry of carbanions generated by both methods will be compared.