Abstract
The electrochemical hydrogenation (ECH) of the biobased platform intermediate cis,cis-muconic acid (ccMA) generates trans-3-hexenedioic acid (t3HDA) with near stoichiometric yields and high faradaic efficiency. This selectivity is independent of the protonation state of the diacid (pH) and of the applied potential. In contrast, a mixture comprised of cis/trans-2-hexenedioic acid, cis/trans-3-hexenedioic acid, and adipic acid was obtained through the thermocatalytic route. We investigated the origins of ECH's exceptional selectivity by combining cyclic voltammetry, bulk electrolysis, isotopic tracing, and theoretical calculations. Trends in reactivity and simple predictors were identified by extending this study to other unsaturated acids.