International Collaboration in Chemistry: Is the Single Transition State Model appropriate for the Fundamental Reactions of Organic Chemistry?

该奖项是根据2009年美国复苏和再投资法案(公法111-5)资助的。国家科学基金会化学部的有机和高分子化学项目支持犹他州州立大学的弗农·D·帕克教授的提议。这项建议是应NSF08-602：美国研究人员与海外同行在化学领域的国际合作(ICC)的邀请而提交的，是与南开大学教授朱晓青和郑金培教授在中国的合作。研究小组将专注于一个对机械有机化学具有深远意义的物理有机化学研究项目。这一提议的科学目标是提供一个问题的答案：“单一过渡态模型是否适合有机化学中的基本反应？”提出这个问题的依据是，Parker教授提出了一些基本的有机反应，包括C-H质子转移反应、氢化物交换反应、卡宾离子-亲核结合反应、中性-阴离子和中性-中性结合反应、SN2反应以及经典的E2消除反应，这些反应都是通过两步反应进行的。两步机构被称为“动力学显著的预联想机构”，以区别于无法从动力学上区分的单步机构的预联想机构。PI的初步非稳态动力学方法，包括“瞬时速率常数分析”和他的假设，即单过渡态模型一般不适合于基本的有机化学反应，并没有得到物理有机化学界的普遍接受。发展了一种新的、极其简单的动力学同位素效应(KIE)机理探针，它明确区分了一步反应机理和具有动力学意义的预缔合反应机理。因此，新方法区分不同的机制，并在不需要评估任何速率常数的情况下，评估具有动力学意义的预缔合机制的KIE。对六种不同的基本反应类型进行了详细研究。更广泛的影响是巨大的，范围从两所大学的学生将接受的出色培训到对物理有机化学领域的重大影响。总体影响是，这一国际项目将促进美利坚合众国和中国两国科学界之间的合作和善意。该项目将为美国国家科学基金会资助培训一支多元化、全球参与的美国科学队伍的努力做出贡献。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).The Organic and Macromolecular Chemistry Program in the Chemistry Division at the National Science Foundation supports a proposal from Professor Vernon D. Parker of Utah State University. This proposal, submitted in response to solicitation NSF 08-602: International Collaboration in Chemistry between US Investigators and their Counterparts Abroad (ICC), is a collaboration with Professors Xiao-Qing Zhu and Jin-Pei Cheng of Nankai University in China. The research team will focus on a research project in physical organic chemistry with profound importance for mechanistic organic chemistry. The scientific objective of this proposal is to provide an answer to the question; "Is the single-transition state model appropriate for the fundamental reactions in organic chemistry?" The basis for the question is that Professor Parker has presented preliminary evidence that several fundamental organic reactions including C-H proton transfer reactions, hydride exchange reactions, carbenium ion-nucleophile combination reactions, neutral-anion and neutral-neutral combination reactions, SN2 reactions as well as the classical E2 elimination reactions take place by a 2-step mechanism. The 2-step mechanism is designated as the "kinetically significant pre-association mechanism" to distinguish it from pre-association mechanisms which cannot be kinetically differentiated from the single-step mechanism. The PI's preliminary non-steady-state kinetic methods including "instantaneous rate constant analysis" and his hypothesis that the single-transition state model is not generally appropriate for the fundamental reactions of organic chemistry, have not gained general acceptance by the physical organic chemistry community. A new and extremely simple kinetic isotope effect (KIE) mechanism probe has been developed, which unambiguously differentiates between 1-step and the kinetically significant pre-association reaction mechanisms. Thus the new method differentiates between the mechanisms and evaluates KIE for the kinetically significant pre-association mechanism without the need to evaluate any rate constants. Detailed studies of six different fundamental reaction types are proposed. The broader impacts are enormous and range from the outstanding training students will receive at both universities to having a large impact on the field of physical organic chemistry. The overall impact is that this international project will foster cooperation and good will between the scientific communities of the United States of America and the People's Republic of China. This project will contribute to the National Science Foundation's effort to fund training of a diverse, globally-engaged, U.S. science workforce.