Department of Chemistry , Stanford University , Stanford , California 94305 , United States.
Center for Plant Aging Research, Institute for Basic Science , Daegu 42988 , Republic of Korea.
J Am Chem Soc. 2019 Jul 10;141(27):10585-10589. doi: 10.1021/jacs.9b03227. Epub 2019 Jun 25.
Bulk water serves as an inert solvent for many chemical and biological reactions. Here, we report a striking exception. We observe that in micrometer-sized water droplets (microdroplets), spontaneous reduction of several organic molecules occurs, pyruvate to lactate, lipoic acid to dihydrolipoic acid, fumarate to succinate, and oxaloacetate to malate. This reduction proceeds in microdroplets without any added electron donors or acceptors and without any applied voltage. In three of the four cases, the reduction efficiency is 90% or greater when the concentration of the dissolved organic species is less than 0.1 μM. None of these reactions occurs spontaneously in bulk water. One example demonstrating the possible broad application of reduction in water microdroplets to organic molecules is the reduction of acetophenone to form 1-phenylethanol. Taken together, these results show that microdroplets provide a new foundation for green chemistry by rendering water molecules to be highly electrochemically active without any added reducing agent or applied potential. In this manner, aqueous microdroplets might have provided a route for abiotic reduction reactions in the prebiotic era, thereby providing organic molecules with a reducing power before the advent of biotic reducing machineries.
大量的水是许多化学和生物反应的惰性溶剂。在这里，我们报告了一个显著的例外。我们观察到，在微米级的水滴（微滴）中，几种有机分子会自发发生还原反应，如丙酮酸还原为乳酸、硫辛酸还原为二氢硫辛酸、延胡索酸还原为琥珀酸、草酰乙酸还原为苹果酸。这种还原反应在没有添加任何电子供体或受体且没有施加电压的微滴中进行。在四种情况中的三种中，当溶解的有机物种的浓度小于 0.1 μM 时，还原效率达到 90%或更高。在大量水中，这些反应都不会自发发生。一个证明还原在水微滴中对有机分子可能具有广泛应用的例子是将苯乙酮还原为 1-苯乙醇。综上所述，这些结果表明，微滴为绿色化学提供了一个新的基础，使水分子具有高度的电化学活性，而无需添加任何还原剂或施加电势。通过这种方式，水微滴可能为前生物时代的非生物还原反应提供了一种途径，从而在生物还原机制出现之前为有机分子提供了还原能力。
