Transient Intermediates in the Gas Phase

华盛顿大学化学系的Frantisek Turecek教授，因其对气相化学反应中瞬态中间体的形成和性质的研究而受到有机和大分子化学计划的支持。与对流层氧化有关的硫氧酸和硝基烷烃自由基的分子和自由基，以及氢原子和羟基自由基向核酸基添加的中间体，都是通过阳离子和阴离子的快速中和产生的，并通过中和-再电离质谱法进行研究。这些研究结合了互补从头算、密度泛函理论和RRKM计算，解决了这些瞬态中间体在基态和激发态的稳定性，并允许分析它们的能量学和单分子解离动力学。化学反应通常是由连续的基本步骤进行的，每一步都产生一个短暂的反应中间体。鉴于这些中间体通常寿命短且浓度低，表征它们是一项艰巨的实验挑战。研究一类特别具有挑战性的瞬态中间体是由高能量过程形成的中间体，如发生在平流层和对流层、燃烧和电离辐射的辐射分解过程中形成的中间体。在有机和大分子化学项目的支持下，华盛顿大学化学系的Frantisek Turecek教授研究了气相化学反应中瞬态中间体的形成和性质。Turecek教授使用中和-再电离质谱法，这是一种“非化学”技术，用于从简单的前体离子中生产所需的中间体，避免了结构上的模糊性，这种模糊性可能是由于他们试图通过其他方法生产而导致的。这些研究，辅以计算分析，解决了这些瞬态中间体的稳定性和反应性，揭示了在高能过程中发生的基本事件。

Professor Frantisek Turecek, of the Department of Chemistry at the University of Washington, is supported by the Organic and Macromolecular Chemistry Program for his studies of the formation and properties of transient intermediates in chemical reactions in the gas phase. Molecules and radicals of sulfur oxyacids and nitroalkane radicals relevant to tropospheric oxidations, and intermediates in the addition of hydrogen atoms and hydroxyl radicals to nucleic bases, are generated by fast neutralization of cations and anions and studied by neutralization-reionization mass spectrometry. These studies, combined with complementary ab initio, density-functional theory, and RRKM calculations, address the stabilities of these transient intermediates in their ground and excited states and permit the analysis of their energetics and the kinetics of their unimolecular dissociation. Chemical reactions often proceed by consecutive elementary steps, each generating a transient and reactive intermediate. Characterization of such intermediates represents a formidable experimental challenge given their typically short lifetimes and low concentrations. An especially challenging class of transient intermediates to study is comprised of those formed by high-energy processes such as those that occur in the stratosphere and troposphere, in combustion, and in radiolysis by ionizing radiation. With the support of the Organic and Macromolecular Chemistry Program, Professor Frantisek Turecek, of the Department of Chemistry at the University of Washington, studies the formation and properties of transient intermediates in chemical reactions in the gas phase. Professor Turecek uses neutralization-reionization mass spectrometry, a `non-chemical` technique, for the production of the desired intermediates from simple precursor ions, avoiding the structural ambiguities which can result from their attempted production by other means. These studies, complemented by computational analyses, address the stabilities and reactivity of these transient intermediates, shedding light on the fundamental events which occur during high-energy processes.