Activity Coefficients at Infinite Dilution for Organic Compounds Dissolved in 1-Alkyl-1-methylpyrrolidinium Bis(trifluoromethylsulfonyl)imide Ionic Liquids Having Six-, Eight-, and Ten-Carbon Alkyl Chains

International audienceActivity coefficients at infinite dilution (gamma(proportional to)(1,2)) for 40 diverse probe solutes, including various (cyclo)alkanes, alkenes, alkynes, aromatic hydrocarbons, alcohols, thiophene, ethers, nitroalkanes, and ketones, were measured by inverse gas chromatography at temperatures from 323 to 343 K in three homologous 1-alkyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ionic liquids (ILs), bearing hexyl, octyl, and decyl side chains. The retention data were further converted to gas-to-IL and water-to-IL partition coefficients using the corresponding gas-to-water partition coefficients. Both sets of partition coefficients were analyzed using the modified Abraham solvation parameter model, with the derived equations tightly correlating the experimental gas-to-IL and water-to-IL partition coefficient data to within average standard deviations of 0.088 and 0.111 log units, respectively

Vaporization Enthalpy and Cluster Species in Gas Phase of 1,1,3,3-Tetramethylguanidinium-Based Ionic Liquids from Computer Simulations

In this work, the study on the volatility of ionic liquids is focused on the 1,1,3,3-tetramethylguanidinium-based ionic liquids. Vaporization enthalpy and cluster species in gas phase for 1,1,3,3-tetramethylguanidinium lactate ([tmgH][L]), 1,1,3,3-tetramethylguanidinium trifluoroacetate ([tmgH][T]), and 1,1,3,3-tetramethylguanidinium formate ([tmgH][F]), are investigated by using molecular dynamic simulation and ab initio calculation, respectively. Results from the molecular dynamic simulations show that the interionic interactions of coulombic electrostatic and Van der Waals forces are the main factors for deciding the volatility. In addition, owing to the change of molecular conformations from the liquid phase to the gas phase, intraionic bond, angle, and torsion interactions also give remarkable contributions. From the ab initio calculations, in the gas phase, an interionic proton transfer easily occurs in the ion pairs of these guanidinium-based ionic liquids, and the ion pairs are finally transformed into more thermodynamically stable neutral molecule dimers (this is different from some imidazolium-based ILs where ion pair can stably exist in gas phase). The transfer energy barriers are very low (typically, less than 2 kJ mol(-1)). However, the existence of a third charged ion ([tmgH](+), [L](-), [T](-), or [F](-)) or neutral molecule (tmg, HL, HT, or HF), will stabilize the ion pairs and prevent the transfer of proton. Finally, the stable trimers are then formed. The tetramers are also stable species. Ab initio results explain why they exist as ions in the liquid state. (C) 2010 American Institute of Chemical Engineers AIChE J, 57: 507-516, 201

Isobaric Vapor–Liquid Equilibrium for Methanol + Dimethyl Carbonate + 1‑Butyl-3-methylimidazolium Dibutylphosphate

Isobaric vapor–liquid equilibrium at 101.3 kPa for the ternary system methanol + dimethyl carbonate +1-butyl-3-methylimidazolium dibutylphosphate ([BMIM]­[DBP]) and their binary systems are determined using a modified Othmer still. By adding [BMIM]­[DBP] into the azeotropic system of methanol + dimethyl carbonate, the relative volatility of dimethyl carbonate is increased, which might be ascribed to the salting-out effect of [BMIM]­[DBP]. The relative volatility α₂₁ increases with increasing molar fraction of [BMIM]­[DBP]. The azeotropic point disappears when the molar fraction of [BMIM]­[DBP] is above 0.150. The equilibrium data are well fitted by the electrolyte nonrandom two-liquid model