(671c) Electrooxidation of Cyclohexene By Halogen Intermediates in a Liquid Diffusion Electrode Cell

Electrocatalysis can significantly reduce fossil fuel resources required for chemical production processes by replacing temperature and pressure with electricity as a driving force, and will become increasingly attractive as renewable energy sources increase the supply and decrease the price of electricity. Electrochemically facilitating these reactions also introduces new process parameters, such as electrolyte pH, electrolyte ion concentration, and operating potential, which can be tuned to optimize efficiency.

One potential candidate for electrification is the field of selective oxidation, which are critical reactions for converting carbon feedstocks into a plethora of important products. For example, epoxides and diols play an important role in the production of essential chemical products including surfactants, epoxies, and pharmaceuticals. Replacing traditional oxidation processes, which often use expensive or toxic catalysts and harsh reagents, with electrochemical processes has the potential to reduce environmental burden while improving safety, and increasing process efficiency. As a further benefit, electrooxidation allows for the use of water as the oxygen source, removing the need for strong and reactive oxidizing agents.

Here, we explore the indirect electrochemical oxidation of cyclohexene towards cyclohexene oxide via halogenated intermediates in a liquid diffusion electrode (LDE) cell. We show that halogen ion identity, concentration, and electrolyte pH play an important role in determining product distribution and Faradaic efficiency, and demonstrate an optimization towards the production of halohydrins, which can be easily epoxidized via further reaction with basic media. Faradaic efficiencies of over 50% towards the corresponding halohydrin are observed, while the application of an LDE cell allows for facile separation of the organic phase containing the halohydrin product.