Conductivity, Viscosity, Spectroscopic Properties of Organic Sulfonic Acid solutions in Ionic Liquids

Abstract

Sulfonic acids in ionic liquids (ILs) are used as catalysts, electrolytes, and solutions for metal extraction. The sulfonic acid ionization states and the solution acid/base properties are critical for these applications. Methane sulfonic acid (MSA) and camphor sulfonic acid (CSA) are dissolved in several IL solutions with and without bis(trifluoromethanesulfonyl)imine (HTFSI). The solutions demonstrated higher conductivities and lower viscosities. Through calorimetry and temperature-dependent conductivity analysis, we found that adding MSA to the IL solution may change both the ion migration activation energy and the number of “free” charge carriers. However, no significant acid ionization or proton transfer was observed in the IL solutions. Raman and IR spectroscopy with computational simulations suggest that the HTFSI forms dimers in the solutions with an N-H-N “bridged” structure, while MSA does not perturb this hydrogen ion solvation structure in the IL solutions. CSA has a lower solubility in the ILs and reduced the IL solution conductivity. However, in IL solutions containing 0.4 M or higher concentration of HTFSI, CSA addition increased the conductivity at low CSA concentrations and reduced it at high concentrations, which may indicate a synergistic effect.

Regioselective Partial Hydrogenation and Deuteration of Tetracyclic (Hetero)aromatic Systems Using a Simple Heterogeneous Catalyst

“…Further lowering of catalyst led to reduced amount of product (entries 3 and 4). Using hexafluoroisopropanol (p K a =9.3 in H 2 O) [21] as solvent instead of AcOH (p K a =4.72 in H 2 O) [22] resulted in just 9 % conversion from 1a to 2a (entry 5). Use of trifluoroacetic acid (p K a =−0.3 in H 2 O) [23] also led to selective reduction of the A‐ring of 1a in excellent yield (entry 6).…”

“…To achieve selective amine formation, we revisited alternative acids. Pleasingly, we found that using 3 equivalents of methanesulfonic acid (MsOH, p K a =−2.6 in H 2 O) [22] in i PrOH allowed for selective formation of 6a in 90 % yield.…”

Novel Colour-Based, Prototype Indicator for Use in High-Pressure Processing (HPP)

“…The above problem was readily resolved by loading the silica gel with water acidified using a small amount of a non-volatile, strong organic acid, such as camphor sulfonic acid, CSA, which has a pK a of ca. 1.2 [31]. In order to test the system with this new additive, the same mass loss vs. applied pressure experiments as described above for the 61 wt% silica gel/PTFE powder mixture were then carried out using instead a silica gel powder loaded with 61wt% of water acidified with CSA and PTFE powder mix, i.e., the same mix as used to prepare the typical pressed discs described in Section 2.2.1 and used in the HPP indicator illustrated in Figure 1.…”

Thermal Hydraulics and Thermochemical Design of Fatty Acid Methyl Ester (Biodiesel) Esterification Reactor by Heating with High Boiling Point Phenyl-Naphthalene Liquid

“…They have many advantages, such as chemical and thermal stability, low flammability, and low vapor pressures [1]. Because of these advantages, ionic liquids have been applied in organic reactions as solvents, catalysts, and liquid thermal storage fluids [2,3]. Ionic liquids are expensive.…”