The nucleophilic opening of an epoxide is a classic organic reaction that has widespread utility in both academic and industrial applications. We have studied the reaction of limonene oxide with morpholine to form 1-methyl-2-morpholino-4-(prop-1-en-2-yl) cyclohexan-1-ol in bulk solution and in electrosprayed microdroplets with a 1:1 v/v water/methanol solvent system. We find that even after 90 min at room temperature, there is no product detected by nuclear magnetic resonance spectroscopy in bulk solution whereas in room-temperature microdroplets (2–3 μm in diameter), the yield is already 0.5% in a flight time of 1 ms as observed by mass spectrometry. This constitutes a rate acceleration of ~ 10⁵ in the microdroplet environment, if we assume that as much as 5% of product is formed in bulk after 90 min of reaction time. We examine how the reaction rate depends on droplet size, solvent composition, sheath gas pressure, and applied voltage. These factors profoundly influence the extent of reaction. This dramatic acceleration is not limited to just one system. We have also found that the nucleophilic opening of cis-stilbene oxide by morpholine is similarly accelerated. Such large acceleration factors in reaction rates suggest the use of microdroplets for ring opening of epoxides in other systems, which may have practical significance if such a procedure could be scaled.

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微滴加速环氧化物的开环

环氧化物的亲核开环是一种经典的有机反应，在学术和工业应用中均具有广泛的用途。我们已经研究了氧化柠檬烯与吗啉在本体溶液和电喷雾微滴中以1：1形成1-甲基-2-吗啉代-4-（丙-1-烯-2-基）环己-1-醇的反应v / v水/甲醇溶剂系统。我们发现，即使在室温下90分钟后，在大体积溶液中也没有通过核磁共振波谱法检测到任何产物，而在室温微滴（直径2–3μm）中，飞行时间为0.5％质谱观察到的1 ms。这构成了〜10 ⁵的速率加速在微滴环境中，如果我们假设90分钟的反应时间后最多有5％的产品散装形成。我们研究了反应速率如何取决于液滴大小，溶剂组成，鞘气压力和施加电压。这些因素深刻影响反应的程度。这种惊人的加速不仅限于一个系统。我们还发现，吗啉对顺式-二氧化苯乙烯的亲核打开也有类似的促进作用。如此大的反应速率加速因子表明在其他系统中使用微滴环氧化物进行开环，如果可以规模化该方法，则可能具有实际意义。