Supercooled micro flows and application for asymmetric synthesis

Abstract

Supercooled micro flow in microchannels was demonstrated. In order to clarify fundamental properties of the supercooling state in microchannels, freezing temperature was measured in the microchannels having widths ranging from 70 µm to 300 µm. The freezing temperature decreased with decreasing width of the microchannel when the microchannel wall was chemically modified with octadecylsilane group. The lowest freezing temperature was observed as −28 °C for water in the 70 µm wide microchannel. By contrast, the freezing temperature was −15 °C and did not depend on width when a microchannel with a bare glass surface was used. Next, the freezing point was measured with flow rates ranging from 0.1 to 2.0 µl min⁻¹ and no dependence on flow rate was observed. Then, the supercooled micro flow was applied to an asymmetric reaction in micro two-phase flow of aqueous and CH₂Cl₂ phases. As expected from thermodynamic prediction, enantiomeric selectivity increased in the supercooled state of water.