Brønsted ionic liquids for sustainable processes: synthesis and physical properties

Abstract

This report describes the synthesis of ionic liquids that incorporate the N-methyl-2-hydroxyethylammonium cation with various carboxylic acid anions and the study of some of their physical properties, including self-diffusion coefficients, density, speed of sound, viscosity, and refractive index. 1H and 13C NMR spectra were used to characterize the chemical structure of the species in concordance with FT-IR spectra. DOSY NMR spectra was used to determine the self-diffusion coefficients of the components, which were consistent with the formation of a lamellar or micellar liquid-crystal phase in samples containing an alkyl chain in the anion species. Thermoacoustic parameters showed that anion alkyl chain has an influence on the molecular packing of these ionic liquids. In addition, the effect of temperature on the properties seems to be related to the size and the type of aliphatic chain of the ionic liquid.