Solvent system switches polarity | Chemical & Engineering News
Volume 83 Issue 35 | p. 27 | Concentrates
Issue Date: August 29, 2005

Solvent system switches polarity

Department: Science & Technology

A solvent system that switches reversibly between non-polar and polar states could facilitate organic syntheses and separations by eliminating the need to remove and replace solvents after each reaction step, according to the chemists who developed it (Nature 2005, 436, 1102). Philip G. Jessop at Queens University, Kingston, Ontario, and coworkers showed that a liquid consisting of an alcohol and an amine converts to an ionic liquid when exposed to carbon dioxide. The liquid is a mixture of 1,8-diaza-bicyclo-[5,4,0]-undec-7-ene (DBU) and 1-hexanol (shown, R = n-hexyl). When CO2 is bubbled through the liquid, the DBU salt of 1-hexylcarbonate is formed, Jessop says. Bubbling N2 or Ar through the salt flushes the CO2, and the ionic liquid reverts to the nonpolar solvent. Both reactions work at room temperature, but the reverse step is faster at around 50 C. Jessop and colleagues suggest that switchable solvents could be applied to green production of high-value chemicals.

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