In situ XAFS investigation of palladium species present during the Heck reaction in room temperature ionic liquids

The Heck reaction, performed in room temperature ionic liquids, has been studied by in situ XAFS, which indicates that palladium clusters of 0.8-1.6 nm diameter are the main species present during reaction.

Alternating copolymerisation of styrene and carbon monoxide in ionic liquids

Room temperature ionic liquids have been used as solvents for the palladium-catalysed copolymerisation of styrene and carbon monoxide. The behaviour of various ionic liquids, the nature and concentration of palladium catalyst, and the reusability of the catalyst-ionic liquid system are discussed. The effects of cation, anion and alkyl chain length of the ionic liquids on the reaction are also addressed. The yield of the polyketone in the ionic liquid systems is enhanced over conventional solvents studied under similar conditions.

Chloride determination in ionic liquids

The determination of chloride impurities in water miscible and water immiscible ionic liquids has been explored using ion chromatography (IC) and cathodic stripping voltammetry (CSV). This paper shows the first quantification of chloride in [NTf2](-) based ILs. The parameters investigated include sample preparation, solvent effect, sample stability, and limit of quantification (LOQ).

A comparative study on the reactivity of electrogenerated bromine with cyclohexene in acetonitrile and the room temperature ionic liquid, 1-butyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide

The reactivity of electrogenerated bromine with cyclohexene has been studied on a platinum microelectrode by linear sweep and cyclic voltammetry in both the room temperature ionic liquid, 1-butyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide, and the conventional aprotic solvent, acetonitrile. Variation in the voltammetric response was observed in the two solvents, indicating that the bromination reaction proceeded via separate mechanisms. To identify the different products, electrolysis was conducted on the preparative scale and NMR spectroscopy confirmed that while bromination of the organic substrate in the ionic liquid yields trans-1,2-dibromocyclohexane, in acetonitrile, trans-1-(N-acetylamino)-2-bromocyclohexane is instead obtained as the major product. The reaction mechanism for bromination in acetonitrile has been modeled using digital simulation.

Electroreduction of oxygen in a series of room temperature ionic liquids composed of group 15-centered cations and anions

The electrochemical reduction of oxygen is reported in four room temperature ionic liquids (RTILs) based on quaternary alkyl -onium cations and heavily fluorinated anions in which the central atom is either nitrogen or phosphorus. Data were collected using cyclic voltammetry and potential step chronoamperometry at gold, platinum, and glassy carbon disk electrodes of micrometer dimension under water-free conditions at a controlled temperature. Analysis via fitting, to appropriate theoretical equations was then carried out to obtain kinetic and thermodynamic information pertaining to the electrochemical processes observed. In the quaternary ammonium electrolytes, reduction of oxygen was found to occur reversibly to give stable superoxide, in an analogous manner to that seen in conventional aprotic solvents such as dimethyl sufoxide and acetonitrile. The most significant difference is in the relative rate of diffusion; the diffusion coefficients of oxygen in the RTILs are an order of magnitude lower than in common organic solvents, and for superoxide these values are reduced by a further factor of 10. In the quaternary phosphonium ionic liquids, however, more complex voltammetry is observed, akin to that expected for the reduction of oxygen in acidified organic media. This is shown to be consistent with the occurrence of a proton abstraction reaction between the electrogenerated superoxide and quaternary alkyl phosphonium cations following the initial electron transfer.

Molecular layering and local order in thin films of 1-alkyl-3-methylimidazolium ionic liquids using X-ray reflectivity

X-ray reflectivity measurements in air of thin films of 1-alkyl-3-methylimidazolium salts in the liquid, liquid crystalline and solid states supported on Si( 111) are described. The films show Bragg features in both liquid crystalline and solid phases, but only after an initial annealing cycle. Kiessig fringes are observed only for the 1-octadecyl-3-methyl-imidazolium hexafluorophosphate films and, following analysis using Parratt32, a bi-layer model is proposed whereby the molecules are orientated with ionic groups at both salt-air and salt-silicon interfaces.

Electroreduction of Chlorine Gas at Platinum Electrodes in Several Room Temperature Ionic Liquids: Evidence of Strong Adsorption on the Electrode Surface Revealed by Unusual Voltammetry in Which Currents Decrease with Increasing Voltage Scan Rates

Voltammetry is reported for chlorine, Cl-2, dissolved in various room temperature ionic liquids using platinum microdisk electrodes. A single reductive voltammetric wave is seen and attributed to the two-electron reduction of chlorine to chloride. Studies of the effect of voltage scan rate reveal uniquely unusual behavior in which the magnitude of the currents decrease with increasing scan rates. A model for this is proposed and shown to indicate the presence of strongly adsorbed species in the electrode reaction mechanism, most likely chlorine atoms, Cl*((ads)).

Friedel-Crafts Benzoylation of Anisole in Ionic Liquids: Catalysis, Separation, and Recycle Studies

The comparison of three ionic liquid-mediated catalytic processes for the benzoylation of anisole with benzoic anhydride is presented. A detailed understanding of the mechanism by which the zeolite and metal triflate reactions in bis{trifluoromethanesulfonyl}imide-based ionic liquids has been reported previously, and these routes are considered together with an indium chloride-based ionic liquid system. Solvent extraction and vacuum/steam distillation have been assessed as possible workup procedures, and an overall preliminary economic evaluation of each overall process is reported. Although the predominant activity is associated with the in situ formation of a homogeneous acid catalyst, the low cost and facile separation of the zeolite-catalysed process leads to this route being the most economically viable overall option. The results of a continuous flow miniplant based on the zeolite catalyst are also presented and compared with the reaction using a small plug How reactor.