Alternative methods for the MnO2 oxidation of codeine methyl ether to thebaine utilizing ionic liquids

The MnO2 oxidation of codeine methyl ether, CME, to thebaine has been accomplished via the use of the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate, bmimBF4. The ionic liquid has been used to remove or extract excess MnO2 and associated impurities from the reaction mixture to afford thebaine in 36 to >95% yield. © 2001 Elsevier Science Ltd. All rights reserved.

Manganese dioxide allylic and benzylic oxidation reactions in ionic liquids

Ionic liquids 1-butyl-3-methylimidazolium tetrafluoroborate [bmIm][BF₄] and 1-butyl-3-methylimidazolium hexafluorophosphate [bmIm][PF₆] were evaluated as reaction media for allylic and benzylic oxidation reactions using manganese dioxide. The use of ionic liquids as an extractant in the reaction work-up was also investigated. Procedures for recycling of the [bmIm][PF₆] ionic liquids used in these MnO₂ oxidation reactions were also developed.

Tunable wettability of polyimide films based on electrostatic self-assembly of ionic liquids

We have demonstrated that the surface wettability of negatively charged polyimide films could be turned by electrostatic self-assembly of ionic liquids. The water contact angles of the polyimide films varied in the range 27-80 degrees for 13 different ionic liquids based on imidazolium and ammonium salts. The surface morphology of the resulting surfaces was characterized using atomic force microscopy. The results revealed that the assembly of longer-substituent cations was characterized by the formation of spherical nanoparticles that were formed due to sequent aggregation of cations on those electrostatically assembled ones via hydrophobic interaction. In this case, the counteranions are present in the assembled layers and the wettability is accordingly affected. Whereas for shorter-substituent cations, no aggregates were formed due to the less hydrophobic interaction than the electrostatic repulsive interaction between the cations, and the counteranions were absent from the assembled layers. This method can also be utilized to quantify the hydrophobicity of various ionic liquids.

Bronsted acidic ionic liquids derived from alkylamines as catalysts and mediums for Fischer esterification : study of structure–activity relationship

Esterification of acetic acid with 1-octanol was studied using a series of alkylammonium salts as Brønsted acidic ionic liquids. The following
ionic liquids were prepared and used as catalysts and mediums in the esterification reaction; [Et₃NH][HSO₄], [Et₃NH][H₂PO₄], [Et₃NH][BF₄],
[Et₃NH][p-CH₃C₆H₄SO₃], [Et₂(PhCH₂)NH][HSO₄], [n-Bu₃NH][HSO₄], [n-Oct₃NH][HSO₄], [Et₂NH₂][HSO₄], [Et₂NH₂][H₂PO₄], [Et₂NH₂]
[BF₄], [i-Pr₂NH₂][HSO₄], [EtNH₃][HSO₄], [EtNH₃][H₂PO₄], and [EtNH₃][BF₄]. Higher acidity of the anion in the ionic liquid resulted in high yield of the ester. Yield of the ester decreased with increase in the size of the cation. There was no phase separation in the reactions where size of anion and/or cation was bigger

Transport properties in ionic liquids and ionic liquid mixtures : the challenges of NMR pulsed field gradient diffusion measurements

Pulsed field gradient NMR is a powerful method for the measurement of diffusion coefficients in liquids and solids and has begun to attract much attention in the ionic liquids field. However, aspects of the methodology as traditionally applied to solutions may not be uniformly applicable in these more viscous and chemically complex systems. In this paper we present data which shows that the Pulsed Gradient Spin Echo (PGSE) method in particular suffers from intrinsic internal gradients and can produce apparent diffusion coefficients which vary by as much as 20% for different ¹H nuclei within a given moleculean obvious anomaly. In contrast, we show that the Pulsed Gradient Stimulated Echo method does not suffer from this problem to the same extent and produces self-consistent data to a high degree of accuracy (better than 1%). This level of significance has allowed the detection, in this work, of subtle mixing effects in [C₃mpyr][NTf₂] and [C₄mpyr][NTf₂] mixtures.

The zwitterion effect in ionic liquids : towards practical rechargeable lithium-metal batteries

Practical lithium-metal batteries are the ultimate goal of battery researchers. The addition of a zwitterionic compound (see Figure) to an ionic liquid electrolyte doped with a lithium salt results in a 100% enhancement of the current densities achieved in the cycling of a lithium-metal cell. This phenomenon arises due to increased lithium-ion mobility or a reduced solid electrolyte interphase layer resistance.

Purification or contamination? The effect of sorbents on ionic liquids

Commonly used for purification, alumina and silica are found to contaminate ionic liquids with particles; these particles cannot be removed easily and can have a non-negligible impact on the electrochemical, spectroscopic and physical properties of an ionic liquid, including its nucleation and crystallisation kinetics.

Use of ionic liquids as electrolytes in electromechanical actuator systems based on inherently conducting polymers

The use of ionic liquids (ILs) as electrolytes for electromechanical actuators based on polypyrroles (PPy's) is described. The composition of the electrolytes has a significant effect on the electrochemical properties of the PPy actuator and subsequently on actuator performance, improving cycle life and strain generated. The actuator performance in ionic liquid electrolytes is significantly better than that in traditional organic and aqueous electrolytes.

A potential novel rapid screening NMR approach to boundary film formation at solid interfaces in contact with ionic liquids

The boundary films generated on a series of inorganic compounds, typical of native films on metal and ceramic surfaces, when exposed to various ionic liquids (ILs) based on the trihexyl(tetradecyl)phosphonium cation have been characterized using multinuclear solid-state NMR. The NMR results indicate that SiO₂ and Mg(OH)₂ interact strongly with the anion and cation of each IL through a mechanism of adsorption of the anion and subsequent close proximity of the cation in a surface double layer (as observed through ¹H−²⁹Si cross polarization experiments). In contrast, Al₂O₃, MgO, ZnO, and ZrO₂ appear less active, strongly suggesting the necessity of hydroxylated surface groups in order to enhance the generation of these interfacial films. Using solid-state NMR to characterize such interfaces not only has the potential to elucidate mechanisms of wear resistance and corrosion protection via ILs, but is also likely to allow their rapid screening for such durability applications.

Liquids intermediate between 'molecular' and 'ionic' liquids : liquid ion pairs?

Ionic liquids comprised of tetradecyltrihexyl- and tetrabutyl- phosphonium cations paired with chloride or sulfonyl amide anions exhibit properties that reflect strong ion association, including comparatively low viscosity as well as a degree of volatility, and hence exemplify an interesting intermediate state between true ionic and true molecular liquids.

Protein solubilising and stabilising ionic liquids

We report a family of biocompatible ionic liquids (ILs) which are able to dissolve significant amounts of proteins such as cytochrome c and in which ATR-FTIR spectroscopy results show retention of secondary structure to extreme temperatures.

Solubility and Stability of cytochrome c in hydrated ionic liquids : effect of oxo acid residues and kosmotropicity

Hydrated ionic liquids (ILs) were prepared by adding appropriate amounts of water to hydrophilic ILs. Some hydrated ILs show excellent solubilizing ability for proteins, keeping the basic properties of ILs. The solubility of cytochrome c (cyt c) depended on the structure of the component ions. When component anions have oxo acid residues, the resulting hydrated ILs solubilize cyt c quite well. In such hydrated ILs, the structure and activity of cyt c is influenced by the kosmotropicity of the component ions. We synthesized ILs from various ions having different kosmotropicity, including dihydrogen phosphate (dhp), dibutylphosphate, acetate, lactate, and methanesulfonate as anions. The activity of the dissolved cyt c depends on the permutations of kosmotropicity of the component ions. cyt c shows no structural change and retains its activity when dissolved in the hydrated choline dhp, which is an excellent combination of chaotropic cation and kosmotropic anion. Furthermore, cyt c dissolved in the hydrated choline dhp remained in a native state and was active after 18 months of storage at room temperature.