Reversible, room-temperature ionic liquids. Amidinium carbamates derived from amidines and aliphatic primary amines with carbon dioxide

A new class of solvents that can be cycled between a room-temperature ionic liquids (RTIL) state and a non-ionic solvent by exposing the liquid mixtures sequentially to 1 atm of carbon dioxide and molecular nitrogen was developed. It was found that the RTILs were more viscous than the non-ionic solvent mixtures from which they were made. It was also found that in the absence of C0 ₂, all of the amidine/arnine combinations, except those with 1,6-diaminohexane, yielded liquid solutions at room temperature. It was also found that the RTIL amidinium carbamates can be employed above room temperature while retaining their reversibility with the non-ionic components in a closed vessel. The results show that reversible, optically active RTILs, whose electrostatic properties can be changed reversibly from relatively low to very high polarity by the addition of different gases, can be used in several interesting applications.