Author
N. Llewellyn Lancaster
Bio: N. Llewellyn Lancaster is an academic researcher from Imperial College London. The author has contributed to research in topics: Ionic liquid & Nucleophile. The author has an hindex of 9, co-authored 13 publications receiving 1149 citations.
Topics: Ionic liquid, Nucleophile, Halide, Bromide, Iodide
Papers
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TL;DR: The reaction of cyclopentadiene with methyl acrylate has been investigated in a range of ionic liquids and the origin of the endo-selectivity for the reactions and associated rate enhancements has been attributed to a hydrogen bond formed between the cation of the ionic liquid and the methyl acid as mentioned in this paper.
262 citations
TL;DR: It was shown that all of the amines are more nucleophilic in the ionic liquids than in the molecular solvents studied in this work, and can be explained in part by the differing hydrogen-bonding properties, as shown by the Kamlet-Taft solvent parameters and the formation of hydrogen bonds between the solvent and the nucleophiles.
Abstract: In this work we report the effect of ionic liquids on a class of charge-neutral nucleophiles. We have studied the reactions of nbutylamine, di-nbutylamine, and tri-nbutylamine with methyl p-nitrobenzenesulfonate in [bmpy][N(Tf)2], [bmpy][OTf], and [bmim][OTf] (bmpy = 1-butyl-1-methylpyrrolidinium; bmim = 1-butyl-3-methylimidazolium) and compared their reactivities, k2, to those for the same reactions in the molecular solvents dichloromethane and acetonitrile. It was shown that all of the amines are more nucleophilic in the ionic liquids than in the molecular solvents studied in this work. Comparison is also made with the effect of ionic liquids on the reactivity of chloride ions, which are deactivated in ionic liquids. The Eyring activation parameters revealed that changes in the activation entropies are largely responsible for the effects seen. This can be explained in part by the differing hydrogen-bonding properties, as shown by the Kamlet−Taft solvent parameters, of each of these solvents and the form...
207 citations
TL;DR: The activation parameters DeltaH(), DeltaS(), and DeltaG() have been estimated for the reaction of chloride in each ionic liquid, and compared to a similar reaction in dichloromethane, where these parameters were found for reaction by both the free ion and the ion pair.
Abstract: In this work, the nucleophilicities of chloride, bromide, and iodide have been determined in the ionic liquids [bmim][N(Tf)2], [bm2im][N(Tf)2], and [bmpy][N(Tf)2] (where bmim = 1-butyl-3-methylimidazolium, bm2im = 1-butyl-2,3-dimethylimidazolium, bmpy = 1-butyl-1-methylpyrrolidinium, and N(Tf)2 = bis(trifluoromethylsulfonyl)imide). It was found that in the [bmim]+ ionic liquid, chloride was the least nucleophilic halide, but that changing the cation of the ionic liquid affected the relative nucleophilicities of the halides. The activation parameters ΔH⧧, ΔS⧧, and ΔG⧧ have been estimated for the reaction of chloride in each ionic liquid, and compared to a similar reaction in dichloromethane, where these parameters were found for reaction by both the free ion and the ion pair.
181 citations
TL;DR: The Kamlet-Taft solvent descriptors have been used to analyze the rates of the reactions, which were found to have a strong inverse dependency on the alpha value of the solvent.
Abstract: In this paper, we report the effect of ionic liquids on substitution reactions using a variety of anionic nucleophiles. We have combined new studies of the reactivity of polyatomic anions, acetate, trifuoroacetate, cyanide, and thiocyanide, with our previous studies of the halides in [C4C1py][Tf2N], [C4C1py][TfO], and [C4C1im][Tf2N] (where [C4C1im]+ is 1-butyl-3-methylimidazolium and [C4C1py]+ is 1-butyl-1-methylpyrrolidinium) and compared their reactivities, k2, to the same reactions in the molecular solvents dichloromethane, dimethylsulfoxide, and methanol. The Kamlet-Taft solvent descriptors (alpha, beta, pi) have been used to analyze the rates of the reactions, which were found to have a strong inverse dependency on the alpha value of the solvent. This result is attributed to the ability of the solvent to hydrogen bond to the nucleophile, so reducing its reactivity. The Eyring activation parameters (DeltaH++ and DeltaS++), while confirming the reaction mechanism, do not offer obvious correlations with the Kamlet-Taft solvent descriptors.
140 citations
TL;DR: Microfluidic devices for spatially localised heating of microchannel environments were designed, fabricated and tested and enable intra-channel temperature control to within +/-0.2 degrees C.
Abstract: Microfluidic devices for spatially localised heating of microchannel environments were designed, fabricated and tested The devices are simple to implement, do not require complex manufacturing steps and enable intra-channel temperature control to within ±02 °C Ionic liquids held in co-running channels are Joule heated with an ac current The nature of the devices means that the internal temperature can be directly assessed in a facile manner
127 citations
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1,656 citations
TL;DR: The alkyl chain length of 1-alkyl-3-methylimidazolium bis(trifluoromethane sulfonyl)imide was varied to prepare a series of room-temperature ionic liquids (RTILs), and the thermal behavior, density, viscosity, self-diffusion coefficients, and ionic conductivity were measured over a wide temperature range.
Abstract: The alkyl chain length of 1-alkyl-3-methylimidazolium bis(trifluoromethane sulfonyl)imide ([Rmim][(CF3SO2)2N], R = methyl (m), ethyl (e), butyl (b), hexyl (C6), and octyl (C8)) was varied to prepare a series of room-temperature ionic liquids (RTILs), and the thermal behavior, density, viscosity, self-diffusion coefficients of the cation and anion, and ionic conductivity were measured over a wide temperature range. The self-diffusion coefficient, viscosity, ionic conductivity, and molar conductivity change with temperature following the Vogel−Fulcher−Tamman equation, and the density shows a linear decrease. The pulsed-field-gradient spin−echo NMR method reveals a higher self-diffusion coefficient for the cation compared to that for the anion over a wide temperature range, even if the cationic radius is larger than that of the anion. The summation of the cationic and anionic diffusion coefficients for the RTILs follows the order [emim][(CF3SO2)2N] > [mmim][(CF3SO2)2N] > [bmim][(CF3SO2)2N] > [C6mim][(CF3SO2)...
1,549 citations
TL;DR: In this paper, a survey on the latest most representative developments and progress concerning ionic liquids, from their fundamental properties to their applications in catalytic processes, is presented, highlighting their emerging use for biomass treatment and transformation.
Abstract: This review gives a survey on the latest most representative developments and progress concerning ionic liquids, from their fundamental properties to their applications in catalytic processes. It also highlights their emerging use for biomass treatment and transformation.
1,471 citations
TL;DR: The current state of the art of the application of ionic liquids in catalysis is reviewed in this article, where examples of the different ways in which ionic liquid have been applied in Catalysis, i.e. as the catalyst itself, as a co-catalyst or catalyst activator, as the source of a new ligand for a catalytic metal centre, or just as the solvent for the reaction.
1,423 citations
TL;DR: The current knowledge about the molecular foundations of IL behavior is discussed and many controversies, speculations, and even myths about the properties that ILs allegedly possess are discussed.
Abstract: Ionic liquids (ILs) are organic salts with melting points near room temperature (or by convention below 100 degrees C). Recently, their unique materials and solvent properties and the growing interest in a sustainable, "green" chemistry has led to an amazing increase in interest in such salts. A huge number of potential cation and anion families and their many substitution patterns allows the desired properties for specific applications to be selected. Because it is impossible to experimentally investigate even a small fraction of the potential cation-anion combinations, a molecular-based understanding of their properties is crucial. However, the unusual complexity of their intermolecular interactions renders molecular-based interpretations difficult, and gives rise to many controversies, speculations, and even myths about the properties that ILs allegedly possess. Herein the current knowledge about the molecular foundations of IL behavior is discussed.
1,393 citations