Search

Carboxylate-anion-based imidazolium ionic liquids (ILs)are powerfulsolvents for cellulose and lignin. However, little is known abouttheir fundamental physicochemical properties. In this work, 1-butyl-3-methylimidazoliumcarboxylate ILs 1-butyl-3-methylimidazolium formate ([C4mim][HCOO]), acetate ([C4mim][CH3COO]), propionate([C4mim][CH3CH2COO]), and butyrate([C4mim][CH3(CH2)2COO]),in which the alkyl chain length in the anions is being varied in contrastto the more usual studies where alkyl chain length in the cationsis varied, have been synthesized and their densities and surface tensionshave been determined experimentally at different temperatures. Byusing these data, the molar volume, isobaric expansivity, standardentropy, lattice energy, surface excess entropy, vaporization enthalpy,and Hildebrand solubility parameter have been estimated for theseILs. From the analysis of structure–property relationship,the effect of alkyl chain length in the anions on these physicochemicalproperties of the ILs has been assessed and the dissolution of celluloseand lignin in these ILs has been discussed. Such knowledge is expectedto be useful for understanding the nature of this class of solventfor the dissolution of biomacromolecules. [ABSTRACT FROM AUTHOR]

Inthis work, four 1-butyl-3-methylimidazolium carboxylate ionicliquids (ILs) with different substituent groups in anions, including1-butyl-3-methylimidazolium glycollate [C4mim][HOCH2COO], 1-butyl-3-methylimidazolium lactate [C4mim][CH3CHOHCOO], 1-butyl-3-methylimidazolium benzoate [C4mim][C6H5COO], and 1-butyl-3-methylimidazoliumglycinate [C4mim][H2NCH2COO], havebeen synthesized and characterized. Their densities (ρ) andsurface tensions (γ) have been determined experimentally inthe temperature range of (298.15 to 343.15) K. By using thermodynamicand empirical equations, molar volume (Vm), isobaric expansivity (αp), standardentropy (S°), lattice energy (UPOT), surface excess entropy (Ss), vaporization enthalpy (ΔlgHm0) and Hildebrand solubility parameter(δH) of these ILs have been derived from densityand surface tension data. The effects of substituent groups in carboxylateanions on densities and surface tensions of these ILs have been assessedfrom the analysis of the structure–property relationship. [ABSTRACT FROM AUTHOR]