Electric fields underlie all reactions and impact reactivity by interacting with the dipoles and net charges of transition states, products, and reactants to modify the free energy landscape. However, they are rarely given deliberate consideration in synthetic design to rationally control reactivity. This Perspective discusses the commonalities of electric field effects across multiple platforms, from enzymes to molecular catalysts, and identifies practical challenges to applying them in synthetic molecular systems to mediate reactivity.

In the last 20 years, biodiesel consumption in the United States has rapidly increased to ∼2 billion gallons per year as a renewable supplement to fossil fuel. However, further expansion of biodiesel use is currently limited in part by poor cold weather performance, which prevents year-round blending and necessitates blend walls ≤5% v/v. In order to provide a diesel fuel blendstock with improved cold weather performance (cloud point, pour point, and cold filter plug point), while at the same time maintaining other required fuel performance specifications, several biodiesel redox analogues were synthesized and tested. The best performing candidate fuels from this class showed improvement in the derived cetane number (29.3% shorter ignition delay), lower heating value (+4.7 MJ/kg), relative sooting tendency (−7.4 YSI/MJ), and cloud point (15 °C lower) when compared to a B100 biodiesel composed of an identical fatty acid profile. It was observed as a general trend that the reduced form of biodiesel, fatty alkyl ethers (FAEs), shows performance improvements in all fuel property metrics. The suite of improved properties provided by FAEs gives biodiesel producers the opportunity to diversify their portfolio of products derived from lipid and alcohol feedstocks to include longchain alkyl ethers, a biodiesel alternative with particular applicability for winter weather conditions across the US.

Combustion of liquid fossil fuels for transportation is a major source of carbon emissions only partially offset by the incumbent renewable alternativesbiodiesel, renewable diesel, and ethanol. New renewable ground transportation fuels derived from abundant sources of biomass, and utilizing carbon-efficient bioprocessing, are needed to further offset fossil fuel use. Low carbon intensity liquid fuels are especially required for medium- to heavy-duty engine architectures supporting the long-range transportation fleet. Realization of substantial carbon efficiency gains in renewable fuel production can be achieved by extending feedstocks beyond lipids, which are the primary bioderived source material for biodiesel and renewable diesel. Toward these ends, chemical upgrading of the high carbon yield, central metabolism-derived intermediates, glycolic acid, lactic acid, and 4-hydroxybutyrate with various fermentation-derived alcohols was accomplished using standard chemical transformations to provide a class of compounds that show promise as an alternative to petroleum diesel. Fuel property testing of these C7–C22 hydroxyalkanoate-derived compounds demonstrated improved cold temperature performance compared to biodiesel (cloud point temperatures < −50 °C) and improved derived cetane number (DCN) and sooting metrics compared to renewable diesel, providing the technical basis for a new high-performance renewable blendstock for decarbonization of heavy-duty transport.

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