(583f) Electrocatalytic Transformation of Organic Substrates

Electrochemical synthesis pathways hold the potential to dramatically reduce the carbon footprint of the chemical industry by replacing heat from fossil fuel combustion with renewable electricity as the driving force for reactions. However, developed electrochemical reactivities primarily focus on the transformation of small inorganic molecules instead of the manipulation of organic compounds which lie at the heart of the chemical industry. Herein, we present approaches to activate C‒H and C‒C bonds in small organic molecules to facilitate more complex reactivities. Among others, these approaches include a mediated pathway to enable C(sp³)‒H bond activation in ethanol while avoiding its overoxidation, opening a novel electrochemical pathway to ethylene oxide from ethanol.

The partial oxidation of ethanol to form ethylene oxide is achieved using a chloride mediated pathway, in which ethanol is first chlorinated to 2‑chloroethanol before undergoing an internal cyclization under alkaline conditions to form the epoxide. The formation of 2-chloroethanol hinges on a key selectivity challenge, as it requires chlorination at the β-carbon while suppressing the thermodynamically more favorable chlorination at the α-carbon. Our experiments show that the selectivity to 2-chloroethanol is significantly impacted by the cell temperature and the applied potential in a manner consistent with a mechanism governed by an initial hydrogen atom transfer from ethanol. Using this insight, we demonstrate how electrode material engineering can further increase the selectivity of this C(sp³)-H bond activation. The precise control the applied potential provides over organic molecule transformation is further shown in the electrocatalytic transformation of unactivated alkanes at room temperature. The insight gained from these demonstrations may be applied to a wide variety of reactions, paving the way for the development of new electrosynthetic pathways.