(62c) Designing Electrolytes for Selective and Sustainable Electrocarboxylation without Using Sacrificial Anodes

Developing ways to mitigate rising CO₂ levels in the atmosphere is crucial for the long-term
future of the planet. Using CO₂ as a synthon in organic synthesis is a promising solution to not
only consume CO₂ but also generate value-added chemicals. While carboxylation reactions with
CO₂ can be powered by renewable electricity, the use of sacrificial metal anodes such as
magnesium and aluminum in the vast majority of electrocarboxylation studies to date limits the
sustainability of these reactions. Aside from preventing oxidation of carboxylation products and
enabling the use of undivided cells, sacrificial anodes stabilize the carboxylate product through
the metal cations produced during its oxidation. These metal cations inhibit the carboxylate
group from nucleophilically attacking the substrate. In this work, we show that adding inorganic
bromide salts and tertiary amines to the catholyte can achieve the same stabilizing functionality
of a sacrificial anode for the electrocarboxylation of aliphatic halides at silver cathodes. The
inorganic cation from the bromide salt stabilizes the carboxylate group, while the tertiary amine
helps prevent cathodic passivation from inorganic carbonates produced from the concurrent
reduction of CO₂ to CO. These results provide guidelines to design more sustainable and
economical electrocarboxylation processes by eliminating the need for sacrificial metal anodes.