Lewis Acidity Of Ionic Liquids Research Articles

Ionic Liquids Catalyzed Friedel–Crafts Alkylation of Substituted Benzenes with CCl4 Toward Trichloromethylarenes

An ionic liquid catalyzed Friedel–Crafts alkylation reaction of substituted benzenes with CCl4 was developed. The reaction proceeded efficiently under mild conditions, gave corresponding trichloromethylarenes with diversity functional groups in moderate to good yields. The influence of Lewis acidity of ionic liquids on the conversion of the alkylation reaction has been investigated. Notably, the probable mechanism of this reaction has been proposed with the assistance of 27Al NMR spectroscopy. It was noteworthy that the predominance of [Al2Cl7]− species in EmimCl–AlCl3, N = 0.67 could be detected by 27Al NMR spectral analysis, and [AlCl4]− was generated at the beginning of reaction. Additionally, it was found that [AlCl4]− could be transformed into [Al2Cl7]− when the reaction finished. Some control experiments confirmed that the interaction between Lewis acidic species [Al2Cl7]− of the ionic liquid and CCl4 led to the change in speciation of aluminum during the alkylation reactions.

Regulating sulfur removal efficiency of fuels by Lewis acidity of ionic liquids

It is urgent to develop a new deep desulfurization process of fuels as the environmental pollution increases seriously. In this work, a series of Lewis acidic ionic liquids (ILs) [C 4 3 MPy]Cl/nZnCl2 (n=1, 1.5, 2, 3) were synthesized and used in extraction and catalytic oxidative desulfurization (ECOD) of the fuels. The effects of the Lewis acidity of ILs, the molar ratio of H2O2/sulfur, temperatures, and different substrates including dibenzothiophene (DBT), benzothiophene (BT) and thiophene (TS), on sulfur removal were investigated. The results indicated that [C 4 3 MPy]Cl/3ZnCl2 presented near 100% DBT removal of model oil under conditions of 323 K, H2O2/DBT molar ratio 6:1. Kinetics for the removal of DBT, BT and TS by the [C 4 3 MPy]Cl/3ZnCl2-H2O2 system at 323 K is first-order with the apparent rate constants of 1.1348, 0.2226 and 0.0609 h-1, and the calculated apparent activation energies for DBT, BT and TS were 61.13, 60.66, and 68.14 kJ/mol from 298 to 308 K, respectively. After six cycles of the regenerated [CC 4 3 MPy]Cl/3ZnCl2, the sulfur removal had a slight decrease. [CC 4 3 MPy]Cl/3ZnCl2 showed a good desulfurization performance under optimal conditions.

A simple, eco-friendly, and recyclable bi-functional acidic ionic liquid catalysts for Beckmann rearrangement

A library of ionic liquids was prepared by varying the cations and anions. Bi-functional acidic ionic liquids were prepared by the direct combination of ionic liquids and ZnCl2. Ionic liquids were investigated in the Beckmann rearrangements. A simple, eco-friendly, and recyclable bi-functional acidic ionic liquid based protocol for Beckmann rearrangement is developed, which is based on the fine tuning of the Brönsted and the Lewis acidity of ionic liquids.

Novel Biodegradable Polyurethane Foams Synthesized via Ring-Opening Oligomerization of Ethylene Carbonate Initiated / Catalyzed by Propylene Glycol / [bmim]Cl-(SnCl<sub>2</sub>) System

Poly ether-carbonate diols were synthesized by ring-opening oligomerization of ethylene carbonate (EC) initiated/catalyzed by propylene glycol/[bmim]Cl-(SnCl2) system. It was shown that the oligomerization was accompanied with decarboxylation and chain cleavage. The stronger the lewis acidity of ionic liquid, the better the catalytic performances. The biogradability of the polyurethane foams which was prepared by poly ether-carbonate diols (or common polyether polyos ZS-4110) and diphenylmethane diisocyanate (MDI) was determined by soil burial and found to be influenced by the content of carbonate unit, molecular weights and the hydroxyl value of polyols respectively. Poly ether-carbonate diols can reduce the amount of MDI in synthesis of polyurethane foams.

Transesterification of dimethyl carbonate with phenol using Brønsted and Lewis acidic ionic liquids

Transesterification reaction of dimethyl carbonate with phenol to methylphenyl carbonate and diphenyl carbonate using dibutyltin oxide catalyst in conjunction with Brønsted and Lewis acidic ionic liquids was studied. It was observed that the use of ionic liquids significantly enhances the yield of diphenyl carbonate. The ionic liquid having p-toluenesulfonate as anion and metal halide (e.g. ZnCl2) as Lewis acid precursor exhibited higher activity and selectivity for diphenyl carbonate formation. Furthermore, the Brønsted and Lewis acidity of ionic liquids was measured by IR spectroscopy using pyridine as a probe and their Lewis acidity order was also determined.

Raman Spectroscopic Study on Solvation of Diphenylcyclopropenone and Phenol Blue in Room Temperature Ionic Liquids

We investigated the solvation of several room temperature ionic liquids by Raman spectroscopy using diphenylcyclopropenone (DPCP) and phenol blue (PB) as probe molecules. We estimated acceptor numbers (AN) of room temperature ionic liquids by an empirical equation associated with the Raman band of DPCP assigned as a C=C stretching mode involving a significant C=O stretching character. According to the dependence of AN on cation and anion species, the Lewis acidity of ionic liquids is considered to come mainly from the cation charge. The frequencies and bandwidths of the C=O and C=N stretching modes of phenol blue are found to be close to those in conventional polar solvents such as methanol and dimethyl sulfoxide. The frequencies of these vibrational modes show similar dependence upon the electronic absorption band center as is observed in conventional liquid solvents. However, peculiar behavior was found in the Raman bandwidths and the excitation wavelength dependence of the C=N stretching mode in room temperature ionic liquids. Both the bandwidth of the C=N stretching mode and the extent of the excitation wavelength dependence of the Raman shift of the C=N stretching mode tend to decrease as the absorption band center decreases, in contrast to the case of conventional solvents. This anomaly is discussed in terms of the properties of room temperature ionic liquids.

Synthesis of diphenylmethane derivatives in Lewis acidic ionic liquids

Diphenylmethane and its derivatives were prepared via Friedel–Crafts benzylation reaction using ionic liquids of 1-butyl-3-methylimidazolium chloride-ZnCl 2 (BmimCl–ZnCl 2), 1-butyl-3-methylimidazolium chloride–FeCl 3 (BmimCl–FeCl 3) and 1-butyl-3-methylimidazolium chloride-FeCl 2 (BmimCl–FeCl 2) as both reaction media and Lewis acid catalysts. In comparison with the reaction performed in conventional organic solvent, faster reaction rate and higher selectivity to target products were achieved in such ionic liquids media. The effects of reaction temperature, reaction time, and the ratio of metal chloride to BmimCl, as well as the amount of ionic liquids on the Friedel–Crafts benzylation were also investigated. It was found that increasing reaction temperature led to high catalytic activity and selectivity, and that the excess amount of Lewis acidity of ionic liquid was detrimental to the reaction. Moreover, these ionic liquids could be conveniently recovered for recycled use; in particular, BmimCl–ZnCl 2 with moisture-stability could be reused at least eight times without loss of catalytic activity.

Determination of the Lewis acidity of ionic liquids by means of an IR spectroscopic probe.

Pyridine and ethanenitrile can be used as molecular probes to measure the Lewis acidities of ionic liquids by monitoring the shift of IR absorption bands near 1450 cm(-1) for pyridine and in the range 2250-2340 cm(-1) for ethanenitrile.