Reversible zwitterionic liquids, the reaction of alkanol guanidines, alkanol amidines, and diamines with CO2

Abstract

Alkanolamidines, alkanolguanidines and diamines each react with CO₂ to form reversible zwitterionic liquids. CO₂ is chemically bound to the alcohol on alkanolamidines and alkanolguanidines as zwitterionic alkylcarbonates, while CO₂ is chemically bound on diamines as zwitterionic carbamates. All three classes of zwitterionic liquids could be reverted to their non-ionic forms by thermally stripping the CO₂ at temperatures near 50 °C, while one derivative was found to irreversibly form a cyclic carbonate.