As a proof of concept, alkene isomerization was selected as a model transformation since only a substoichiometric amount of Co-H is required for the reaction to proceed with complete conversion. Alkene 1 was selected for the initial optimization of the electrochemical HAT (e-HAT). Trial runs using the literature precedents for classical HAT isomerization with alkene 1 provided poor conversion to the desired product. For example, the use of 50 mol% of silane and 10 mol% of cobalt catalyst in benzene gives 29% yield of the desired product and 7% of other chain-walking isomers (entry 1, Shenvi's protocol). The method of Norton, which relies on a high pressure of hydrogen gas, delivered only traces of product (entry 2). First forays into e-HAT isomerization followed the guiding principles from prior findings in electrochemistry and HAT chemistry to aid in the selection of proper ligands, cathodic materials and proton sources. An abbreviated summary of over 200 experiments is depicted in Figure (see SI for an extensive list). First, the cobalt catalyst screening (entries 3-6) revealed that CoBr2(glyme) was optimal, resulting in efficient Co-H generation with the highest yield for the alkene isomerization. However, the mass balance of these reactions consisted of a mixture of chain-walking and reduction byproducts. Thus, ligand screening was performed to cleanly obtain the desired single isomerization product (entries 7-10). Although 4,4'-dimethoxy-bipyridine cleanly afforded the desired selective 1position isomerization, the conversion was low (38% yield + 33% recovered 1, entry 10). In order to improve the conversion while retaining the ligand-controlled selectivity, various proton sources within a wide range of pKa were explored (entries 10-13); the use of inexpensive triethylamine hydrotetrafluoroborate (3 equiv., entry 13) as a proton source emerged as optimum, providing the desired product 2 in 72% isolated yield. This unique proton source was employed due to its ability to function as a supporting electrolyte as well; its inclusion was crucial to the reproducibility and robustness of the reaction. The final set of e-HAT conditions tolerates moisture and leads to completion with catalytic amounts of electricity (0.5 F/mol, entry 14), and can be set up in minutes using a simple undivided cell and a commercial potentiostat. Interestingly, similar reactivity was not observed when conventional reductants, such as zinc and manganese, were used (entries 15-16). Of all cathodes evaluated, tin, Nifoam, glassy-carbon, and stainless steel could be employed, but a tin cathode gave the highest yield across a broad range of substrates (see SI). With these results in hand, the scope of the e-HAT isomerization of monosubstituted olefins was investigated (Table ). A wide range of functionalities was tolerated, including free and protected amines (3, 6), anilines (5), amides (4), lactams (7), alcohols (13), and nitriles (14) with over 80% yield on average. In addition, the e-HAT isomerization exhibited a broad scope across a range of different arenes. Under optimized conditions, alkenes were isomerized in the presence of a pyridine (8), a thiophene (9), an electron-deficient indole (10), a redox-active aryl bromide (11), and an aryl-BPin (2). Remarkably, this method can deliver the isomerization of an allylic ether to the corresponding enol ether adduct (16). Terminal disubstituted olefins were however, untouched by the bipyridine complex (Conditions A). As a result, another round of optimization was conducted revealing that Co II (t-Bu,t-Bu-cyclohexylsalen) (Co(salen)-1) could be employed to exclusively isomerize such olefins to the thermodynamic trisubstituted alkenes by using HFIP (hexafluoroisopropanol) as the proton source and a Ni-foam cathode in acetone (Conditions B, see SI for optimization). As e-HAT relies on the in-situ formation of a cobalthydride, chemoselective reactions are thus possible simply by tuning conditions. A similarly broad scope was observed for this isomerization as well (17-25). The ability to achieve olefin isomerizations in the presence of free phenols, pyridines, anilines, nitriles, and epoxides is without precedent. In addition, the generation of -unsaturated amides has not been previously reported by isomerization methods, presumably due to a tendency to isomerize into conjugation.