Unexpected Strong Acidity Enhancing the Effect in Protic Ionic Liquids Quantified by Equilibrium Acidity Studies: A Crucial Role of Cation Structures on Dictating the Solvation Properties.

The equilibrium acidities for several series of structural and electronic different organic acids were measured in 3-pyrrolidinium-based aprotic and protic ionic liquid (IL) analogues, that is, [Bmpy][NTf], [BpyH][NTf], and [PyH][NTf], by the UV-Vis method. The acidities of neutral acids are found to be much stronger in the protic ILs (PILs) than aprotic ILs (AILs), and the acidifying effect in the two PILs roughly increases proportionally to the number of protons in the cation of the PIL. On the other hand, interestingly, the cationic N-H acids exhibit similar acidities in [Bmpy][NTf] and [BpyH][NTf] but much weaker than those in [PyH][NTf].

CO Absorption by DBU-Based Protic Ionic Liquids: Basicity of Anion Dictates the Absorption Capacity and Mechanism.

PILs are promising solvent systems for CO absorption and transformations. Although previously tremendous work has been paid to synthesize functionalized PILs to achieve a high-performance absorption, the underlying mechanisms are far less investigated and still not clear. In this work, a series of DBU-based PILs, i.

Equilibrium Acidities of Nitroalkanes in an Ionic Liquid.

The acidity ladder scale in [BMPY][NTf] was successfully expanded toward the weak acidity region for about five more p K units compared to the previously established one. This allows the acidities of a series of 13 aliphatic and aromatic nitroalkanes to be determined accurately by the UV-vis spectroscopic method. The acidity of nitroalkane in [BMPY][NTf] covers ∼8 p K units and is significantly weaker than those in DMSO and water.

Unexpected solvation-stabilisation of ions in a protic ionic liquid: insights disclosed by a bond energetic study.

Equilibrium acidities (ps) of 42 organic acids were precisely determined in protic ionic liquid (PIL) [DBUH][OTf]. Surprisingly, the often seen homoassociation complication during the p measurement of O-H acids in DMSO was not detected in [DBUH][OTf], implying that the incipient oxanion should be better solvation-stabilized by the PIL, although its "apparent" dielectric constant is much lower than that of the conventional molecular solvent DMSO. Evidence showing that the solute ions in the PIL are also free from other specific ion associations like ion-pairing is further demonstrated by the identical ps of protic amine salts bearing largely different counter-anions.

Design and Applications of N-tert-Butyl Sulfinyl Squaramide Catalysts.

A new chiral HBD system, N-tert-butyl sulfinyl squaramide, was designed and synthesized. The core N-tert-butyl sulfinyl squaramide with an 1-aminoindan-2-ol skeleton was found to be an efficient catalyst in the enantioselective Friedel-Crafts alkylation of indoles and acyl phosphonates.