The selective, mild oxidation of alkanes has been a major goal of catalytic research for decades and could impact chemical manufacturing in challenges from late-state CH bond functionalization to selective conversion of feedstock hydrocarbons. In oxygenation reactions, such as the reaction of cyclohexane and meta-chloroperbenzoic acid (mCPBA), both thermodynamic and kinetic challenges face selective catalysis because (a) oxidation typically gives stabilized products and (b) weaker C-H bonds of oxidized products are more reactive toward further oxidation. Thus, mixtures of alcohol, ketone, and ester are typically obtained. Moreover, most first-row metal catalysts for such reactions can operate through a number of mechanisms, which vary based on conditions, metal center, and ligands. In order to better understand the relationships between these variables, we have systematically studied reaction concentration profiles for the oxidation of hydrocarbons using a series of ToMMX catalysts (ToM= tris(4,4-dimethyl-2-oxazoline)phenyl borate; M = Fe – Cu). The kinetic data collection has been automated, and the features that cause errors in concentration profiles have been minimized. The complexity of these reaction mechanisms means that dramatic changes in conversion, product distributions, and turnover frequencies can occur when changes are made in solvent, order of reagent/substrate addition, and rates of addition. By automating our studies as much as possible and studying the kinetics of these systems we have been able to make valuable insights into the complex reaction mechanisms occurring with our catalytic reaction systems.

Oxidation of cyclohexane: Kinetic studies of a series of ToMMX catalysts

2019 Fall National Meeting

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