Reactive Systems at the Onset of Microsolvation

微溶剂化开始时的反应系统

• 批准号: 0132584
• 负责人: Kenneth Leopold
• 金额: $ 34.96万
• 依托单位: University of Minnesota-Twin Cities
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-03-01 至 2006-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0132584&HistoricalAwards=false
• 关键词: Reactive; Systems; Onset; Microsolvation

AbstractProposal: CHE-0132584PI: Leopold, Kenneth R.The effect of solvation on molecular structure and reactivity is an important problem in chemistry. The investigation of microsolvated species offers a valuable means of bridging gas phase measurements with studies of condensed matter. Such work offers the possibility of developing an increasingly accurate molecular-level description of solvation. In this project, rotational spectroscopy will be used to examine the effects of microsolvation on reactive acid-base complexes. Molecular structures and dipole moments will be determined from rotational constants and Stark effect data, respectively. Aspects of charge distribution will, in certain cases, also be revealed by nuclear hyperfine structure. Two classes of systems are targeted: (i) partially bound Lewis acid-base complexes, whose structure and bonding change dramatically upon crystallization and (ii) hydrogen bonded systems which undergo proton transfer in solution or in the crystalline phase. These systems are chosen because in both cases, aggregation promotes chemical change and the effects of microsolvation are, therefore, expected to be pronounced. The central question to be addressed in this work is , "In systems for which aggregation drives chemical change, how big is the effect of the first near neighbor?". Several systems with higher degrees of solvation are also considered. This work will systematically exploit the hypersensitivity of these reactive acid-base complexes to their near-neighbor interactions for the purpose of investigating "solvation" effects at the small cluster level.Much of the chemistry important to human activity involves substances in solution. For example, the chemistry of living things, reactions in contaminated ground waters, and even a host of important industrial processes occur only when molecules are dissolved in a solvent. When such reactions occur, the solvent itself is not a direct participant in the chemistry, though it has become increasingly clear that its presence can play a significant role in mediating the reactions that take place. Thus, in this project, we are interested in studying the role of solvent in mediating chemical processes. Our approach is to gain a basic understanding of the problem by examining the effect of a single solvent molecule close to a pair of reactive molecules. To accomplish this, we isolate two reacting molecules, plus one solvent molecule, and use microwaves to investigate how the solvent affects them. Understanding the influence of a single solvent molecule is an important step, as it is the fundamental building block for understanding the influence of the many solvent molecules present in a real solution. Moreover, the basic knowledge gained from this work may have direct consequences for modeling difficult problems of societal importance, e.g., the formation of particles in the earth's atmosphere, whose presence has wide ranging effects on climate, ozone levels, and human health. In this way, we envision potential practical applications for the fundamental science addressed in this project. Graduate students at the University of Minnesota will participate in this research as part of their training toward the doctoral degree and will learn numerous technical skills applicable to a wide variety of problems.

Abstract Propopal：CHE-0132584PI：Leopold，Kenneth R.溶剂化对分子结构和反应性的影响是化学中的重要问题。对微透明物种的研究提供了一种有价值的方法，可以通过凝结物质的研究弥合气相测量。这样的工作提供了开发日益准确的分子级溶剂化描述的可能性。在该项目中，旋转光谱法将用于检查微透明化对反应性酸碱复合物的影响。分子结构和偶极矩将分别从旋转常数和鲜明的效应数据确定。在某些情况下，电荷分布的各个方面也将通过核超细结构来揭示。两类系统是针对的：（i）部分结合的路易斯酸碱复合物，其结构和粘结在结晶时发生了巨大变化，以及（ii）在溶液中或结晶相中经历质子转移的氢键系统。之所以选择这些系统，是因为在这两种情况下，聚集都会促进化学变化，因此预计将明显微覆盖。这项工作要解决的主要问题是：“在哪种聚集驱动化学变化的系统中，第一个邻居邻居的效果有多大？”还考虑了几种具有较高溶剂化程度的系统。这项工作将系统地利用这些反应性酸碱复合物的超敏反应，以便在小簇水平上研究“溶剂化”作用。例如，只有在分子溶解在溶剂中时，才发生生物的化学，污染地面水的反应，甚至许多重要的工业过程。当发生这种反应时，溶剂本身并不是化学的直接参与者，尽管越来越清楚其存在可以在介导发生的反应中发挥重要作用。因此，在这个项目中，我们有兴趣研究溶剂在介导化学过程中的作用。我们的方法是通过检查接近一对反应性分子的单个溶剂分子的效果来获得对问题的基本理解。为此，我们隔离了两个反应分子，再加上一个溶剂分子，并使用微波来研究溶剂如何影响它们。了解单个溶剂分子的影响是一个重要的步骤，因为它是理解真实溶液中许多溶剂分子的影响的基本构建块。此外，从这项工作中获得的基本知识可能会导致建模社会重要性的困难问题，例如，地球大气中的颗粒形成，其存在对气候，臭氧水平和人类健康的影响很大。通过这种方式，我们设想了该项目中涉及的基本科学的潜在实用应用。明尼苏达大学的研究生将参加这项研究，这是他们攻读博士学位的一部分，并将学习适用于各种问题的许多技术技能。