Aryloxenium Cations

在这个由化学系化学结构，动力学和机制-B（CSDM-B）计划支持的项目中，普渡大学的Hilkka Mittamaa和John Nash教授将研究芳氧阳离子，这是一类广泛的高活性化合物，其化学性质知之甚少。这些阳离子是许多重要的化学和生物反应的关键中间体，例如酚和烷烃的氧化，工业热塑性塑料（加热时不软化的塑料）的产生，以及生物学中通过脱卤过氧化物酶进行的氧化卤代酚脱卤。Oxenium阳离子也与天体化学研究有关，被认为存在于星际空间。尽管它们很重要，但由于在溶液中产生和研究它们的困难，对它们的反应性的知识受到严重限制。因此，尽管芳氧鎓离子已经被研究了40多年，但令人惊讶的是，人们对它们的基本化学反应性知之甚少。在这项研究中获得的信息，不仅有利于合理利用的芳氧阳离子在有机合成和工业应用，但也将使设计的芳氧阳离子与特定的应用定制的性能。在这个项目的教育活动将包括提高研究生和本科生的科学成长，包括学生属于代表性不足的群体，通过多样化的研究经验。因此，这项研究有助于使STEM劳动力多样化。参与该项目的研究生将参加工业或政府实习，这不仅会扩大知识面，而且往往还会增加就业机会。这些相互作用预计将导致与工业和政府实验室的伙伴关系，促进技术转让给这些实验室。详细的动力学气相反应性研究芳氧阳离子将进行，以提高其化学性质的理解。芳氧阳离子是一种新型的含不完全电子壳层的带正电荷的一价氧原子的阳离子。尽管对这些化合物有广泛的基本和实际兴趣，但对它们的反应性知之甚少。本项目将利用离子阱质谱仪中进行的气相离子分子反应来探索其化学性质。将使用作用光谱来验证它们的结构。将鉴定与各种不同试剂而不仅仅是溶剂（以前不可能）的芳氧鎓离子反应产物。芳氧阳离子的反应速率将提供目前无法获得的详细动力学反应性信息。研究结构变化对芳氧阳离子反应性的影响，以及不同电子基态的芳氧阳离子的反应性，将有助于芳氧阳离子反应性研究的发展。实验研究将辅以高水平的量子化学计算，以加深我们对观察到的反应性的理解。该奖项反映了NSF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。

In this project supported by the Chemical Structure, Dynamics, and Mechanisms-B (CSDM-B) Program of the Chemistry Division, Professors Hilkka Kenttamaa and John Nash of Purdue University will investigate aryloxenium cations, a broad class of highly reactive compounds, whose chemistry is poorly understood. These cations are the key intermediates in many important chemical and biological reactions, such as the oxidation of phenols and alkanes, the generation of industrial thermoplastics (plastics that do not soften on heating), and the oxidative halophenol dehalogenation by dehaloperoxidase in biology. Oxenium cations have also been implicated in astrochemical studies and are thought to persist in interstellar space. Despite their importance, knowledge on their reactivity is severely limited due to difficulties in generating and studying them in solution. Therefore, although aryloxenium ions have been investigated for more than 40 years, surprisingly little is known about their fundamental chemical reactivity. The information obtained in this research will not only facilitate the rational utilization of aryloxenium cations in organic synthesis and industrial applications but will also enable the design of aryloxenium cations with tailored properties for specific applications. Educational activities in this project will include enhancing the scientific growth of graduate and undergraduate students, including students belonging to underrepresented groups, via a diverse research experience. Hence, this research helps to diversify the STEM workforce. Graduate students involved in this project will participate in industrial or government internships, which not only leads to intellectual broadening but often also to enhanced employment opportunities. These interactions are expected to lead to partnerships with industry and government laboratories, facilitating technology transfer to these laboratories.Detailed kinetic gas-phase reactivity studies on aryloxenium cations will be performed in order to improve the understanding of their chemical properties. Aryloxenium cations are novel species which contain a formally positively charged, monovalent oxygen atom with an incomplete electron shell. In spite of broad fundamental and practical interests in these compounds, relatively little is known about their reactivity. This project will utilize gas-phase ion-molecule reactions performed in ion trap mass spectrometers to explore their chemical properties. Action spectroscopy will be used to verify their structures. Aryloxenium ion reaction products with a variety of different reagents and not just solvents (not possible previously) will be identified. Rates of the reactions of aryloxenium cations will provide detailed kinetic reactivity information that is currently unavailable. The study of the influence of structural changes on the reactivity of aryloxenium cations and the examination of the reactivities of aryloxenium ions with different electronic ground states will facilitate the development of novel reactivity paradigms for aryloxenium cations. The experimental studies will be complemented by high-level quantum chemical calculations in order to deepen our understanding on the observed reactivity.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.