Catalysis with One Hand

建议没有。： cts9813937 pi: David S. Sholl, Andrew J. Gellman机构：卡内基梅隆大学标题：单手催化教授David S. Sholl和Andrew Gellman试图了解手性表面的特征，确定多相催化中的对映体选择性。他们将利用表面科学、量子化学和蒙特卡罗技术来实现这一目标。他们的第一个目标是研究天然手性表面的化学吸附和表面反应，如Ag(643)S, Cu(643)S, Pt(643)S和Ag(643)R, Cu(643)R, Pt(643)R，它们具有S和R构型。计算和测量解吸能、吸附物取向角和反应速率常数的差异，以便分离和量化每种相互作用在吸附-解吸对映体分化中的作用。对映体纯吸附剂将由烷基氯化物、仲醇或叔醇、烯烃、腈和取代芳烃组成。LEED将用于表征表面，IRAS用于确定吸附质取向，TPD用于测量脱附能。利用半经验电位，分子-表面和分子间的相互作用将被参数化，并调整到烷基氯吸附的实验测量。蒙特卡罗模拟将提供吸附物质的能量和取向，以便研究表面覆盖和吸附物大小对对映体分化的影响。扩展哈克分子轨道（EHMO）理论将用于醇、酮和烯烃在天然手性铜和铂表面的吸附。第二个目标是通过吸附手性模板修饰非手性表面（如Pt（111）和Cu(111)），以模拟和量化产生对映特异性行为的相互作用类型。模板将由R或S构型的热稳定分子通过氧或亚甲基与金属结合，并含有侧基，如烷基，乙烯基，苯基等。共吸附物将由可逆结合的单功能物质组成，如伯醇、酮和腈。相互作用能将用TPD测量。利用基团-表面和功能-功能相互作用的半经验势，以及EHMO理论和蒙特卡罗模拟，从理论上研究官能团之间的相互作用，以获得吸附物的取向和解吸能。第三个目的是研究对映体特异性表面的表面化学。一系列具有良好表征的扭结和阶梯表面的醇将用于研究结构因素，如吸附质相对于选择位点之间的间距的相对大小。对各种表面、模板和共吸附剂组合的能量和分子取向的理论预测将用于指导实验。最终目标是产生产生对映体分化的表面和分子间相互作用的基本知识。这些知识可用于指导多相对映选择性催化剂的设计。这项理论实验研究将涉及对学生的训练。

Proposal No.: CTS-9813937PI: David S. Sholl, Andrew J. GellmanInstitution: Carnegie Mellon UniversityTitle: Catalysis with One HandProfessors David Sholl and Andrew Gellman seek to understand the characteristics of chiral surfaces that determine enantioselectivity in heterogeneous catalysis. They will pursue this goal using surface science, quantum chemical and Monte Carlo techniques. Their first objective is to study chemisorption and surface reactions on naturally chiral surfaces, such as Ag(643)S, Cu(643)S, Pt(643)S and Ag(643)R, Cu(643)R, Pt(643)R, which have S and R configurations. The differences in desorption energies, adsorbate orientation angles and reaction rate constants will be calculated and measured, in order to isolate and quantify the role of each type of interaction in adsorption-desorption enantiodifferentiation. Enantiomerically pure adsorbates will consist of alkyl chlorides, secondary or tertiary alcohols, alkenes, nitriles, and substituted aromatics. LEED will be used to characterize the surfaces, IRAS to determine adsorbate orientation, and TPD to measure desorption energy. Utilizing semiempirical potentials, molecule-surface and intermolecular interactions will be parametrized and adjusted to experimental measurements of alkyl chloride adsorption. Monte-Carlo simulations will afford the energy and orientation of adsorbed species in order to study surface coverage and adsorbate size effects on enantiodifferentiation. Extended Huckel Molecular Orbital (EHMO) theory will be used in the case of alcohol, ketone and alkene adsorption on naturally chiral Cu and Pt surfaces. The second objective is to modify achiral surfaces (such as Pt(111) and Cu(111)) by adsorption of a chiral template, to model and quantify the types of interaction producing enantiospecific behavior. Templates will consist of R or S configurations of thermally stable molecules bound to the metal through oxygen or methylene groups, and containing side groups such as alkyl, vinyl, phenyl, etc.. Co-adsorbates will consist of reversible bound monofunctional species such as primary alcohols, ketones and nitriles. Interaction energies will be measured using TPD. The interaction between functional groups will be studied theoretically utilizing semiempirical potentials for group-surface and function-function interactions, as well as EHMO theory and Monte-Carlo simulation to obtain adsorbate orientation and desorption energy.The third objective is to investigate the surface chemistry of enantiospecific surfaces. Series of alcohols on well-characterized kinked and stepped surfaces will be used to study structural factors such as relative size of adsorbate with respect to spacing between selective sites. Theoretical prediction of energies and molecular orientation for various combinations of surfaces, templates and co-adsorbents will be used to guide the experimentation.The final goal is to generate fundamental knowledge of the surface and intermolecular interactions that produce enantiodifferentiation. Such knowledge could be used to guide the design of heterogeneous enantioselective catalysts. This theorico-experimental research will involve the training of students.