Roles of Contact Ion-Pairs as Promoters or Catalysts in Organic Reactions

美国国家科学基金会化学部的化学合成项目支持路易斯维尔大学的Gerald B. Hammond教授的研究、教育和推广项目。这个项目正在寻求对依赖于离子（带电粒子）形成的化学反应的新理解。在离子反应中，离子可以分离（解离），也可以形成接触离子对（几乎没有分离）。有些溶剂很容易支持离子的解离（例如，水中的食盐）。其他溶剂不允许离子离解（例如，油中的食盐）。本研究旨在了解溶剂的性质如何影响离子的形成和分离，以及离子的分离如何影响反应产物的形成。将实验结果与各种计算结果相结合，预测溶液中离子/离子对的结构。哈蒙德博士通过他的“瞄准卓越：西班牙裔拉丁裔学生倡议”激励西班牙裔学生进入化学和其他科学领域，该倡议将杰出的西班牙裔化学带到大学作为榜样。他还与拉丁美洲大学化学系的教师建立联系，以吸引高水平的研究活跃的科学家和学生参与合作项目。哈蒙德教授与加州州立大学弗雷斯诺分校合作，接待本科生进行暑期研究，并与中国东华大学的徐波教授合作。在化学部化学催化项目的资助下，肯塔基州路易斯维尔大学的杰拉尔德·b·哈蒙德博士正在研究离子反应。在离子反应中，离子可以解离或形成含离子对。本研究考察了在低介电常数和低溶剂化功率的溶剂中，接触离子对如何在化学反应中与反应物和催化剂相互作用。离子转化涵盖了广泛的反应类型，从简单的亲核取代到复杂的阳离子过渡金属催化，但对反离子效应的理解主要局限于单个反应。为了实现这一目标，他的研究产生了各种金属和非金属基团的反离子亲和尺度，并实现了一种新的接触离子对辅助亲核取代过程（SNip）。这种概念上的新亲核取代途径在常规SN2或SN1反应失败的情况下使反应具有活性。对剪切过程进行了计算研究。此外，还研究了离子对启动子的设计，包括手性离子对启动子和更好的亲电试剂，以促进剪切过程。哈蒙德博士积极参与外展项目，专注于通过暑期研究实习将代表性不足的学生招募到技术领域。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The Chemical Synthesis Program of the NSF Chemistry Division supports the research, education, and outreach programs of Professor Gerald B. Hammond of the University of Louisville. This project is seeks new understanding of chemical reactions that rely on the formation of ions (charged particles). In an ionic reaction, ions can separate (dissociate) or they can form contact ion pairs (where they are just barely separated). Some solvents easily support the dissociation of ions (e.g., table salt in water). Other solvents do not allow ions to dissociate (e.g., table salt in oil). This research seeks to understand how the properties of the solvent affect the ion formation and separation and subsequently, how ion separation impacts the formation of reaction products. Experimental results are combined with various computational efforts to predict the structures of the ions/ion pairs in solution. Dr. Hammond inspires Hispanic students to enter chemistry and other science fields through his "Targeting Excellence: Hispanic Latino Student Initiative" which brings prominent Hispanic chemistry to the University to serve as role models. He is also establishing links with faculty in chemistry departments from Latin American Universities to attract high caliber research-active scientists and students in collaborative projects. Professor Hammond works with the California State University, Fresno to host undergraduate students for summer research and also collaborates with Professor Bo Xu, of Donghua University, China. With funding from the Chemical Catalysis Program of the Chemistry Division, Dr. Gerald B. Hammond, of the University of Louisville in Kentucky, is investigating ionic reactions. In an ionic reaction, ions can be dissociated or they can form contain ion pairs. This research examines how, in low dielectric constant and low solvation power solvents, contact ion pairs interact with reactants and catalysts in a chemical reaction. Ionic transformations cover a wide range of reaction types, from simple nucleophilic substitutions to complex cationic transition metal catalysis, but the understanding of counterion effects is mainly circumscribed to individual reactions. Toward this goal, his investigations generate affinity scales of counterions for various metal and non-metal groups and implement a new contact ion pair-assisted nucleophilic substitution process (SNip). This conceptually new nucleophilic substitution pathway enables reactivity in those instances where conventional SN2 or SN1 reactions fail. Computational studies of the SNip process are conducted. Also, under investigation is the design of ion pair promoters including chiral ion pair promoters and better electrophiles to facilitate the SNip process. Dr. Hammond is keenly engaged in outreach programs focused on underrepresented student recruitment into the technical fields through summer research internships.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.