Enthalpy of Solution of 1-Octyl-3-methylimidazolium Tetrafluoroborate in Water and in Aqueous Sodium Fluoride

Abstract

An adiabatic calorimeter was used to measure the enthalpy of solution of 1-octyl-3-methylimidazolium tetrafluoroborate (0.0035 mol·kg-1 to 0.02 mol·kg-1) in water and in aqueous sodium fluoride of different ionic strengths (0.1 mol·kg-1 to 0.43 mol·kg-1) at nominal temperatures of 298 K, 306 K, and 313 K. Two additional measurements of the enthalpy of solution of 1-butyl-3-methylimidazolium tetrafluoroborate (0.013 mol·kg-1) in water at 298 K are also reported. The present results lead to the standard-state changes of enthalpy and heat capacity for the solution process. The contribution of a methylene group to the enthalpy of solution of these ionic liquids was determined from the measurements and is shown to be in agreement with the value obtained from other classes of organic compounds. The enthalpy of solution increment for the methylene group is used to calculate the enthalpy of solution of the series of 1-alkyl-3-methylimidazolium tetrafluoroborates. Calculated standard-state heat capacity values for the aqueous solution process and the aqueous solute are also given. Potential micelle formation of 1-octyl-3-methylimidazolium tetrafluoroborate in water was examined.

Extraction, Preconcentration and Isolation of Flavonoids from Apocynum venetum L. Leaves Using Ionic Liquid-Based Ultrasonic-Assisted Extraction Coupled with an Aqueous Biphasic System

“…Although [C4mim]BF4 was commonly used as the extractant in IL-UAE [18,[33][34][35], some research groups had reported that tetrafluoroborate-based ILs were not water-stable as they could undergo hydrolysis in aqueous solution [36,37] …”

“…In addition, it was reported that the factors influencing the extraction ability are very complicated, hydrogen-bonding ability can be the main factor influencing the extraction considering the anions [31], π-π and n-π interactions also should not be omitted in view of imidazole ring-containing cations [32]. Although [C 4 mim]BF 4 was commonly used as the extractant in IL-UAE [18,[33][34][35], some research groups had reported that tetrafluoroborate-based ILs were not water-stable as they could undergo hydrolysis in aqueous solution [36,37] …”

Mutual Solubility of Hydrophobic Ionic Liquids and Water in Liquid-Liquid Two-phase Systems for Analytical Chemistry

“…221 Special care must be exercised when acquiring reliable data for ILs composed of these anions. 222 Recent physicochemical data reported in literature are mainly on ILs that are stable in aqueous media, such as those based on bis(trifluoromethylsulfonyl)imide. [223][224][225][226][227] 2·1 Mutual solubilities of moderately hydrophobic ILs and water 73,[226][227][228] that is, the linear variation of the logarithm of the solubility of both water and ILs with the alkyl chain length of [Cnmim + ].…”

Synthesis, characterization, and application of 1-butyl-3-methylimidazolium thiocyanate for extractive desulfurization of liquid fuel

“…The first studies focused on ILs containing the [PF 6 ] − and [BF 4 ] − anions (Zhang and Zhang 2002;Zhang et al 2004). However, these ILs are prone to hydrolyze even in the presence of humidity, generating hazardous hydrolysis products (Swatloski et al 2003;Archer et al 2005).…”