Insights into the levulinate-based ionic liquid class: synthesis, cellulose dissolution evaluation and ecotoxicity assessment
Novel ammonium, phosphonium and imidazolium ionic liquids (ILs) based on levulinic acid as the anion were prepared and characterized (NMR spectroscopy, FT-IR spectroscopy, TGA, and viscosity). Commercial methyl carbonate precursors were employed to access the target levulinate ILs via a quick, one-step synthetic procedure that does not require the use of halogenated solvents or produce any waste water. The ability of the levulinate ILs to dissolve cellulose was investigated in detail. Provided the right conditions are employed, these ILs display good to remarkable dissolution ability toward their parent polysaccharide. In particular, [EMIM][Lev] is able to dissolve 29 wt% cellulose at 100 °C, which increases to 38 wt% under reduced pressure. For the best performing IL, several variations of the dissolution conditions, which are known to prevent potential side reactions of the imidazolium cation, have also been tested. The ecotoxicity of the prepared ILs as well as of the previously reported protic levulinate ILs has also been assessed by means of both freshwater and seawater model organisms belonging to different steps of the trophic chain.