Synthesis and properties of reversible ionic liquids using CO2, mono- to multiple functionalization

New carbamate based ionic liquids were prepared using different primary amines such as aliphatic, aryl-, di-, and triamines in the presence of organic superbase and CO2 atmosphere. Many of the prepared compounds can be considered as ionic liquids with low melting points. The reaction conditions based on solvent, type of base, pressure, reaction time, and temperature were optimized and discussed. Tetramethylguanidine (TMG) can be envisaged as an alternative base in order to obtain high yields and purities of carbamate salts specially when primary amines and polyamines are used. The reversibility studies using n-octylamine/DBU and n-octylamine/tetramethylguanidine systems were performed. These studies showed that tetramethylguanidine can lead to more reversible systems while DBU can lead to more stable salts.