Transition States in Polar Solvents. A Kinetic Isotope Effect Study

华盛顿大学的J.Kurz的这一项目得到了有机动力学项目的支持，旨在更好地了解溶剂分子在某些取代反应中的作用。这个问题将通过观察到的同位素取代反应速度的变化来研究。将继续调查最近观察到的对化学反应速率的反常同位素效应的根源。这些反常的同位素效应适用于极性溶剂中的甲基转移反应；它们似乎意味着，在甲基转移到不带电荷的氧亲核试剂的过程中，成键和溶剂化的变化是高度不同步的。为了适应这些数据，将需要对当前的物理有机理论或当前解释动力学同位素效应的方法进行一些修订。这些反常效应的来源将通过(A)对已知出现反常的反应速率和模型反应的速率和平衡的成套同位素效应的测量，(B)隐含的成键/溶剂化不同步的可观察后果的理论估计，以及(C)对过渡态力场进行计算机模拟，这是定量解释这些同位素效应所必需的。

This project by J. Kurz of Washington University is supported by the Organic Dynamics Program, and is aimed at a better understanding of the role of solvent molecules in certain substitution reactions. This problem will be investigated by the observed changes in the rate of the reactions upon isotopic substitution. Investigations will continue into the origins of the recently observed anomalous isotope effects on the rates of chemical reactions. These anomalous isotope effects are for methyl transfer reactions in polar solvents; they seem to imply that during methyl transfer to an uncharged oxygen nucleophile, changes in bonding and solvation are highly asynchronous. In order to accommodate these data, some revision will be required: either of current physical organic theory, or of current approaches to the interpretation of kinetic isotope effects. The origin of these anomalous effects will be elucidated by (a) measurements of complete sets of isotope effects on the rates of reactions that are known to present anomalies, and on the rates and equilibria of model reactions, (b) the theoretical estimations of observable consequences of the implied bonding/solvation asynchronies, and (c) the computer modeling of transition state force fields that is required for the quantitative interpretation of those sets of isotope effects.