Dynamics of Mediated Electrochemical Synthesis in Microemulsions

CTS-9632391本项目的目标是对电极上的表面动力学和微乳液中的动力学如何影响介导式电化学合成中的反应活性控制有一个基本的了解。电化学研究用于将表面活性剂和反应物在电极表面的吸附-脱附动力学与催化反应速率联系起来。介体反应包括碳-碳偶联、环化和生成烯烃。使用裸碳电极的介质在主体流体中的催化效率将与专为在微乳液中实现高反应速率而设计的新催化电极的催化效率进行比较。大环金属络合物通过有效的内球途径催化反应，如维生素B12和钴、铁和镍的卟啉，用作介体。将基于聚合物硅-氧-碳连接到碳电极的逐层电极涂层策略与先前开发的聚合物沉积方法进行了比较。电分析方法用于比较微乳液、均相有机溶剂和催化电极中的反应速度。在搅拌间歇电化学反应器中使用合成电解液进行产物分析，以评估系统的实用价值，并优化产率和反应物转化率。微乳液的组成和催化涂层的性能被调整，以获得关键反应的最佳反应速度和产率。用时间分辨流动伏安法测定了反应物和表面活性剂在裸电极和催化电极上的表面动力学。本文采用了前人发展起来的方法和理论。共吸附质之间的分子相互作用将通过从波伏安法获得的Frumkin相互作用参数来评估。作为介体反应速率的可能限制因素，使用电活性探针估算了新催化膜的反应物和表面活性剂的进出速率。寻求所有表面动力学事件的速率和中介合成反应的速率之间的关联。这项工作的目的是为未来在相对廉价、低毒、水基流体介质中设计高效的介电合成过程提供基本指导。介导的电化学反应是主要的目标，因为这些原子经济的过程可以用来制备许多种类的化学物质，包括内酯、信息素、前列腺素、C-糖苷、光学活性烯烃和醇以及环状分子。专门为微乳液设计的新型催化表面与流体组成的动力学控制相结合，可能为未来高价值化学品的合成提供成本效益高、环境友好的工艺基础。

ABSTRACT CTS-9632391 The goal of this project is to develop a fundamental understanding of how surface dynamics on electrodes and kinetics in microemulsions influence control of reactivity in mediated electrochemical syntheses. Electrochemical studies are used to relate surfactant and reactant adsorption-desorption dynamics on electrode surf aces to catalytic reaction rates. The mediated reactions include carbon-carbon coupling, cyclizations, and olefin production. Catalytic efficiencies of mediators in the bulk fluid using bare carbon electrodes will be compared with those of new catalytic electrodes designed specifically to achieve high reaction rates in microemulsions. Macrocyclic metal complexes that catalyze reactions by efficient inner sphere pathways, such as vitamin B12 and Cobalt-, iron-, and nickel-porphyrins, are used as mediators. Layer-by-layer electrode coating strategies based on polymeric silicon-oxygen-carbon linkages to carbon electrodes are compared with a previously developed polymer deposition method. Electroanalytical methods are used to compare reaction rates in microemulsions and homogeneous organic solvents and catalytic electrodes. Synthetic electrolyses in a stirred batch electrochemical reactor with product analysis are used to assess the practical utility of the systems, and to optimize yields and reactant conversion rates. Compositions of microemulsions and properties of catalytic coatings are tuned for best reaction rates and yields for key reactions. Surface dynamics of reactants and surfactants on electrodes are measured by time-resolved flow voltammetry on bare and catalytic electrodes. Methods and theory developed earlier are employed. Molecular interactions between co-adsorbates will be assessed via Frumkin interaction parameters obtained from wave voltammetry. As possible limiting factors for the rates of mediated reactions, reactant and surfactant exit and entry rates are estimated for the new catalytic films using electroactive probes. Correlations between rates of all surface dynamic events and rates of mediated synthetic reactions are sought. The objective of this work is to provide fundamental guidance for the future design of efficient mediated electrochemical synthetic processes in relatively inexpensive, low toxicity, water-based fluid media. Mediated electrochemical addition reactions are major targets because these atom-economical processes can be utilized to prepare chemicals of many classes, including lactones, pheromones, prostaglandins, C-glycosides, optically active olefins and alcohols, and cyclic molecules. New catalytic surfaces design specifically for microemulsions combined with kinetic control by fluid composition may provide a basis for future cost-effective, environmentally benign processes for the synthesis of high value chemicals.