While the flow rate employed was quite low (0.12 mL/min of toluene), the residence time was less than 14 seconds. In 2002, Jähnisch and co-workers reported the first microflow chlorination of 2,4-diisocyano-1-methylbenzene, which used a falling-film reactor developed by IMM. We found that the substrate contamination with water negatively influenced the performance of the C–H chlorination.įlow C–H chlorination using a compact flow reactor is highly desirable in terms of efficiency and safety in handling highly toxic gases such as chlorine. At a higher conversion of ethylene carbonate such as 61%, the selectivity for monochlorinated ethylene carbonate over dichlorinated ethylene carbonate was 86%. Near-complete selectivity for single chlorination required the low conversion of ethylene carbonate such as 9%, which was controlled by limited introduction of chlorine gas. The partial irradiation of the flow channels also sufficed for the C–H chlorination, which is consistent with the requirement of photoirradiation for the purpose of radical initiation. Such short time of exposition sufficed the photo C–H chlorination. When ethylene carbonate was introduced to the reactor, the residence time was measured to be 15 or 30 s, depending on the slope of the reactor set at 15 or 5°, respectively. The setup employed sloped channels so as to make the liquid phase thinner, ensuring a high surface-to-volume ratio. A novel photoflow setup designed for a gas–liquid biphasic reaction turned out to be useful for the direct use of chlorine gas. We report the high-speed C–H chlorination of ethylene carbonate, which gives chloroethylene carbonate, a precursor to vinylene carbonate.
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