Effect of Structure of Room Temperature Ionic Liquids on Organic Reactions Involving Electrochemically Generated Superoxide Ions

摘要：约翰·W.作者：Michael A.马修斯和约翰·莫尼耶机构：南卡罗来纳大学提案编号：0500032标题：室温离子液体结构对涉及电化学产生的超氧离子的有机反应的影响项目摘要：智力价值：该项目旨在为有机底物的选择性部分氧化的新颖和可持续的方法提供科学依据。 该方法利用电化学手段在高导电性、非挥发性室温离子液体（RTIL）溶剂中产生超氧离子（O2O-），然后利用O2O-进行随后的均相反应。 这项工作的前提是RTIL结构的合理设计将允许选择性控制O2O-的形成和随后的部分氧化。因此，本项目的科学目标是确定RTIL是稳定的电化学产生的O2O-的存在下，进行某些有机氧化反应的RTIL的广泛类别，并与阴离子和阳离子的RTIL的结构，这些反应的速率和产率。 这将涉及识别反应产物和测量涉及O2O-的选定有机反应的固有动力学。 感兴趣的三类有机反应是：（1）羧酸和酮，分别通过伯醇和仲醇的氧化产生;（2）碳酸酯和氨基甲酸酯，分别在二氧化碳存在下由醇和胺产生;和（3）多卤代芳族化合物（例如多氯联苯）的氧化。 所有这些反应的第一步是在RTIL中电化学产生O_2 O_-。 在NSF探索性资助的支持下，PI表明，只要RTIL的结构和纯度得到控制，RTIL中就可以产生稳定的O2O-物质。 此外，O2O-与苯甲醇、二苯甲醇、二氧化碳和六氯苯反应形成所需产物。 他们还表明，RTIL阳离子结构的微小变化会显著影响产物产率。 此外，优选的阳离子取决于反应。 例如，在咪唑钥环的2位添加甲基将二苯甲醇到二苯甲酮的平均产率从50%增加到98%以上。 同样重要的是，没有检测到RTIL的降解以及这些高产率沿着。相比之下，O2 O-与苯甲醇反应形成苯甲酸的产率从23%降低到0.0%，表明RTIL引起的反应抑制。 迄今为止使用的PF 6阴离子的长期稳定性也存在问题，因为它经受电解和水解，产生与O2O-反应的氢氟酸。 虽然到目前为止的结果是非常有希望的，有没有一个先验的方法来知道哪个RTIL是适当的，少得多的最佳，对于一个给定的反应。为了将给定的反应与适当的RTIL匹配，需要了解RTIL结构对均相反应速率和产率的影响。 人们希望发现的基本知识，将确定RTIL，在O2O-和有利的溶剂催化性能的存在下，具有长期稳定性。因此，PI计划将阴离子和阳离子结构与其在产物产率和固有反应速率中的作用联系起来，用于本项目中三个重要有机反应类别中的代表性反应。这将使得能够为给定反应合理选择RTIL。 更广泛的影响：这项工作将加速使用新的和潜在的环境友好的策略，为电有机化学合成。 RTIL不仅是有前途的绿色溶剂，而且超氧化物电化学在室温下利用空气或氧气和电。因此，RTIL技术与电化学的结合促进了用于有机中间体制造或氯代芳烃修复的环境友好技术的发展。该项目将与一个招收少数民族博士的项目挂钩。学生通过斯隆基金会少数民族博士奖学金，已经到位了几年。 少数族裔博士南卡罗来纳州的学生受益于南卡罗来纳州非裔美国人教授项目，该项目将少数民族学生和教师导师配对。 南加州大学的本科生将参加NSF赞助的研究通信工作室（NSF EEC 0212244，PI博士迈克尔马修斯），提供技术出版和演示的指导。来自其他大学的本科生将通过正在进行的NSF本科生研究经验（REU）计划参与化学工程系的污染预防（NSF-EEC-0097695，PI博士约翰·韦奇）。

ABSTRACTPI: John W. Weidner, Michael A. Matthews and John Monnier Institution: University of South CarolinaProposal Number: 0500032Title: Effect of Structure of Room Temperature Ionic Liquids on Organic Reactions Involving Electrochemically Generated Superoxide Ion Project Summary: Intellectual merit: This project is aimed at providing the scientific basis for a novel and sustainable approach for the selective, partial oxidation of organic substrates. The approach utilizes electrochemical means to generate the superoxide ion (O2o-) in highly conducting, non-volatile room-temperature ionic liquid (RTIL) solvents, and then utilizes O2o- to carry out subsequent homogeneous reactions. The premise of this work is that the rational design of RTIL structures will allow selective control of O2o- formation and subsequent partial oxidation. Therefore, the scientific objectives of this project are to identify RTILs that are stable in the presence of electrochemically generated O2o-, conduct certain organic oxidation reactions in broad classes of RTILs, and relate the structure of the anion and cation of the RTIL to the rate and yield of these reactions. This will involve identifying reaction products and measuring intrinsic kinetics of selected organic reactions involving O2o-. The three classes of organic reactions of interest are: (1) carboxylic acids and ketones, produced by oxidation of primary and secondary alcohols, respectively; (2) carbonates and carbamates, produced from alcohols and amines, respectively, in the presence of carbon dioxide; and (3) oxidation of polyhalogenated aromatics, (e.g. polychlorinated biphenyls). The first step in all these reactions is the electrochemical generation of O2o- in RTILs. With prior support from an exploratory NSF grant, the PIs showed that a stable O2o- species can be generated in RTILs as long as the structure and purity of the RTIL are controlled. Further, O2o- reacts with benzyl alcohol, benzhydrol, carbon dioxide, and hexachlorobenzene to form the desired products. They also showed that small changes in the structure of the RTIL cation dramatically affect product yield. In addition, the preferred cation depends on the reaction. For example, adding a methyl group in the position 2 of the imidazolium ring increased the average yield of benzhydrol to benzophenone from 50% to over 98%. Equally significant was that no degradation of the RTIL was detected along with these high yields. In contrast, the reaction of O2o- with benzyl alcohol to form benzoic acid decreased the yield from 23% to 0.0%, indicating reaction inhibition caused by the RTIL. There is also a problem with the long-term stability of the PF6 anion used to date since it is subject to electrolysis and hydrolysis, producing hydrofluoric acid that reacts with O2o-. While the results to date are very promising, there is no a priori way to know which RTIL is appropriate, much less optimal, for a given reaction. To match a given reaction with an appropriate RTIL, there is a need to understand the effect of RTIL structure on homogeneous reaction rates and yield. It is desired to discover the fundamental knowledge that will identify RTILs that have both long-term stability in the presence of O2o- and favorable solvent catalytic properties. Therefore, the PIs plan to relate anion and cation structure to their role in product yield and intrinsic reaction rates, for representative reactions within three important classes of organic reactions in this project. This will enable a rational choice of an RTIL for a given reaction. Broader impacts: This work will accelerate the use of novel and potentially environmentally friendly strategies for electro-organic chemical syntheses. Not only are RTILs promising green solvents, but superoxide electrochemistry utilizes air or oxygen and electricity at room temperature. Thus the combination of RTIL technology with electrochemistry promotes the development of an environmentally friendly technology for either the manufacturing of organic intermediates, or the remediation of chlorinated aromatics. The project will be linked with a program to recruit minority Ph.D. students through Sloan Foundation Minority Doctoral Fellowships that have been in place for several years. Minority Ph.D. students at the University of South Carolina (USC) benefit from the USC African American Professors Program (AAPP), which pairs minority students and faculty mentors. USC undergraduates will participate in the NSF-Sponsored Research Communications Studio (NSF EEC 0212244, PI Dr. Michael Matthews), which provides instruction in technical publishing and presenting. Undergraduates from other universities will participate through the ongoing NSF Research Experience for Undergraduate (REU) program in the Department of Chemical Engineering in the area of pollution prevention (NSF-EEC-0097695, PI Dr. John Weidner).