How stable are Ionic Liquids?
Generally Ionic Liquids show remarkably high thermal stabilities of > 200°C. A decomposition pathway of the usually very stable imidazolium-based Ionic Liquid is the back alkylation of the anion. The back reaction depends on the nucleophilicity of the anion at which temperature this reaction occurs. It has been determined that onset measurements from DSC alone are not suitable to determine the thermal stability. A more valuable indication is provided by TGA analysis which shows the loss of weight due to the distillation of the volatile alkylating agents. For EMIM Acetate the temperature at which 10% loss of weight is observed is for example 215 °C. EMIM Methanesulfonate or EMIM Ethylsulfate show higher thermal stabilities with corresponding decomposition temperatures of 330 °C. Under basic conditions imidazolium-based Ionic Liquids tend to form carbenes, which can undergo further decomposition, like irreversible disproportionation.
