Thermomorphic System Research Articles

Homogenous Liquid–Liquid Extraction of Au(III) from Acidic Medium by Ionic Liquid Thermomorphic Systems

Two ionic liquid (IL) thermomorphic systems were designed. The thermoregulated property exhibited by the IL systems was utilized for the recovery of Au(III) from acidic medium. The cloud point order of the two ILs was proposed and evidenced via a combination of experimental measurements and quantum chemical calculations. The impacts of salt ions and acid on the thermomorphic phase behavior of the IL–H₂O binary mixture system were investigated. After comprehensive comparison, a systematic study of Au(III) extraction by the [Suc][Tf₂N]₂ (succinyl bis(trifluoromethylsulfonyl)imide) system was carried out because of its outstanding hydrophobicity and extraction ability. Then, a comparison between traditional liquid–liquid extraction (TLLE) and homogeneous liquid–liquid extraction (HLLE) was made during the process of optimization of various extraction parameters. In addition, the anion-exchange mechanism in the extraction process was revealed. The thermoregulated [Suc][Tf₂N]₂ system presented an excellent selectivity for Au(III) in a solution of coexisting multimetallic ions. Finally, Au(III) was almost completely stripped from the loaded IL phase by oxalic acid. The extraction efficiency of Au(III) using regenerated IL still maintains a surprising stability after five turns of cycling experiments. Hence, the dicationic IL [Suc][Tf₂N]₂ was regarded as a potential extractant for the recovery of gold.

A Novel Thermomorphic System for Electrocatalytic Diels‐Alder Reactions

Summary of main observation and conclusionThe discovery that lithium bis(trifluoromethane)sulfonamide (LiTFSI)/1‐nitropropane (PrNO2) solution functions as a less polar alternative to lithium perchlorate (LiClO4)/nitromethane (MeNO2) solution has led to the development of a novel thermomorphic system for electrocatalytic Diels‐Alder reactions. Methyl cyclohexane (Me‐c‐Hex) can form a monophasic condition with LiTFSI/PrNO2 solution at room temperature, enabling the use of hydrophobic dienophiles. After the electrochemical reaction, a biphasic condition can be formed at –50°C, where the cycloadducts are selectively recovered from the upper Me‐c‐Hex phase and the remaining lower LiTFSI/PrNO2 solution can be reused.

Direct Ordering of Anchoring Events at the Surface of Iron Oxide Nanoparticles Enabled by A Stepwise Phase‐Transfer Strategy

AbstractFor most nanoparticle applications, understanding the “strength” of anchoring events at the surface is necessary to design effective ligand exchange processes. The present report demonstrates the ability to direct the ordering of phosphonic acid, catechol, and carboxylic acid as anchoring groups for iron oxide nanoparticles, enabled by a stepwise phase‐transfer strategy. A key feature was the use of a cyclohexane‐based thermomorphic system that provided a unique homogeneous field for ligand‐exchange processes, where hydrophobic nanoparticles and a hydrophilic ligand, or hydrophilic nanoparticles and a hydrophobic ligand, effectively mixed together within a moderate temperature range.

Obtaining glycerol carbonate and glycols using thermomorphic systems based on glycerol and cyclic organic carbonates: Kinetic studies

Glycerol carbonate has mostly been synthesized by transesterification of glycerol with dimethyl carbonate and ethylene carbonate. We propose to obtain it using propylene and butylene carbonate as co-substrates with Na2CO3 as catalyst, also generating 1,2-propanediol and 1,2-butanediol. The reactants exhibit thermomorphic behavior, so we capitalized on this feature to avoid mass transfer limitations instead of using co-solvents. The kinetics of both reactions were studied, obtaining activation energies and deactivation constants of 67.13±1.82kJmol−1 and 0.14±0.02min−1 for the reaction between glycerol and propylene carbonate and 58.56±1.10kJmol−1 and 0.39±0.03min−1 for the reaction of glycerol with butylene carbonate.

Temperature-Responsive Ionic Liquids: Fundamental Behaviors and Catalytic Applications.

Temperature-responsive ionic liquids (ILs), their fundanmental behaviors, and catalytic applications were introduced, especially the concepts of upper critical solution temperature (UCST) and lower critical solution temperature (LCST). It is described that, during a catalytic reaction, they form a homogeneous mixture with the reactants and products at reaction temperature but separate from them afterward at ambient conditions. It is shown that this behavior offers an effective alternative approach to overcome gas/liquid-solid interface mass transfer limitations in many catalytic transformations. It should be noted that IL-based thermomorphic systems are rarely elaborated until now, especially in the field of catalytic applications. The aim of this article is to provide a comprehensive review about thermomorphic mixtures of an IL with H2O and/or organic compounds. Special focus is laid on their temperature dependence concerning UCST and LCST behavior, including systems with conventional ILs, metal-containing ILs, polymerized ILs, as well as the thermomorphic behavior induced via host-guest complexation. A wide range of applications using thermoregulated IL systems in chemical catalytic reactions as well as enzymatic catalysis were also demonstrated in detail. The conclusion is drawn that, due to their highly attractive behavior, thermoregulated ILs have already and will find more applications, not only in catalysis but also in other areas.

Overview of the effect of salts on biphasic ionic liquid/water solvent extraction systems: anion exchange, mutual solubility, and thermomorphic properties.

Hydrophobic (water-immiscible) ionic liquids (ILs) are frequently used as organic phase in solvent extraction studies. These biphasic IL/water extraction systems often also contain metal salts or mineral acids, which can significantly affect the IL trough (un)wanted anion exchange and changes in the solubility of IL in the aqueous phase. In the case of thermomorphic systems, variations in the cloud point temperature are also observed. All these effects have important repercussions on the choice of IL, suitable for a certain extraction system. In this paper, a complete overview of the implications of metal salts on biphasic IL/water systems is given. Using the Hofmeister series as a starting point, a range of intuitive prediction models are introduced, supported by experimental evidence for several hydrophobic ILs, relevant to solvent extraction. Particular emphasis is placed on the IL betainium bis(trifluoromethylsulfonyl)imide [Hbet][Tf2N]. The aim of this work is to provide a comprehensive interpretation of the observed effects of metal salts, so that it can be used to predict the effect on any given biphasic IL/water system instead of relying on case-by-case reports. These prediction tools for the impact of metal salts can be useful to optimize IL synthesis procedures, extraction systems and thermomorphic properties. Some new insights are also provided for the rational design of ILs with UCST or LCST behavior based on the choice of IL anion.

Cycloalkane-based thermomorphic systems for organic electrochemistry: an application to Kolbe-coupling

The discovery that cycloalkanes can form thermomorphic systems with typical polar organic solvents has led to the development of less-polar electrolyte solutions. Their mixing and separation can be regulated reversibly at a moderate temperature range. The phase switching temperature can be controlled by changing the solvent compositions. While biphasic conditions are maintained below the phase switching temperature, conductive monophasic conditions as less-polar electrolyte solutions are obtained above the phase switching temperature. After the electrochemical transformations, biphasic conditions are reconstructed below the phase switching temperature, facilitating the separation of cycloalkane where hydrophobic products or designed hydrophobic platforms are selectively partitioned. Several polar organic solvents, including acetonitrile, methanol, and pyridine, can be used in this system according to the requirement of the reactions.

A Cycloalkane-based Thermomorphic System for Organocatalytic Cyclopropanation Using Ammonium Ylides

Abstract Highly polar ammonium ylide intermediates derived from α-halocarbonyl compounds were successfully trapped by cycloalkane phase-tagged activated alkenes via a cycloalkane-based thermomorphic (CBT) process, which allows for facile product isolation using a single liquid–liquid extraction step to effectively generate cyclopropane libraries in the cyclohexane phase.

ChemInform Abstract: A Cycloalkane‐Based Thermomorphic System for Palladium‐Catalyzed Cross‐Coupling Reactions.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

A cycloalkane-based thermomorphic system for palladium-catalyzed cross-coupling reactions

In this paper, we describe a practical and efficient protocol for Sonogashira, Suzuki–Miyaura, and Mizoroki–Heck cross-coupling using a CBT system. The use of substrates with cycloalkane-soluble tags facilitates separation of the desired products and the homogeneous Pd catalyst via simple liquid–liquid extraction, thereby eliminating the need for a catalyst removal process.

Solution-phase oligosaccharide synthesis in a cycloalkane-based thermomorphic system

The cycloalkane-based thermomorphic (CBT) system is a convenient and practical method for oligosaccharide synthesis, and hydrophobically modified oligosaccharides have a remarkable affinity for CBT solutions composed of methylcyclohexane and propionitrile.

Thermomorphic System with Non‐Fluorous Phase‐Tagged Ru(BINAP) Catalyst: Facile Liquid/Solid Catalyst Separation and Application in Asymmetric Hydrogenation.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Novel Densely Alkylated Hydroxyl‐Functional Polyvinylpyrrolidone Showing Phase‐Selective Solubility

AbstractSummary: Polyvinylpyrrolidone (PVP) is a commonly used polymer with many different applications in the pharmaceutical, cosmetic and food industries. However, the lack of reactive groups and the difficulty in copolymerizing the monomer, N‐vinylpyrrolidin‐2‐one (NVP) with most other monomers, limits the possibility of modifying the physical and chemical properties of the polymer. Monomers that are derivatives of NVP itself are expected to show small differences in radical reactivity as compared to the parent monomer and provide a way of adjusting the polymer properties without extensive compositional drift during copolymerization. Here we present the synthesis of two new functionalized NVP‐based monomers and their copolymerization with alkylated NVP‐monomers for the preparation of two functionalized PVPs with phase‐selective solubility in heptane. Both copolymers showed 99.99% selective solubility in heptane over DMF (thermomorphic system) and 99.99% in heptane over 90% EtOH‐H2O (latent biphasic system). These results suggest that the polymers could be used as soluble supports to facilitate recovery and recycling of catalysts or reagents from liquid/liquid systems after homogeneous reactions.Phase‐selectively soluble polyvinylpyrrolidone copolymer.magnified imagePhase‐selectively soluble polyvinylpyrrolidone copolymer.

Thermomorphic System with Non-Fluorous Phase-Tagged Ru(BINAP) Catalyst: Facile Liquid/Solid Catalyst Separation and Application in Asymmetric Hydrogenation

The thermomorphic BINAP derivative 1 tagged with long alkyl chains was prepared from (S)-5,5'-diamino BINAP and applied to Ru-catalyzed asymmetric hydrogenation of beta-ketoesters under homogeneous conditions in 3:1 (v/v) ethanol/1,4-dioxane at 60 degrees C with high enantioselectivity (up to 98% ee). Results indicated that the Ru(1) catalyst was easily recovered by simple cooling and precipitation and could be used for at least four cycles without any loss of enantioselectivity.

Cycloalkane-based Thermomorphic Electrochemical Reaction System Composed of Nitrile-solvents

Combination of cyclohexane and nitriles in the presence of electrolytes were found to realize an effective, biphasic thermomorphic system that enable practical applications of electrochemical reactions featuring high current density followed by rapid product/electrolyte separation.

Palladium–Platinum Bimetallic Nanoparticle Catalysts Using Dendron Assembly for Selective Hydrogenation of Dienes and Their Application to Thermomorphic System

Abstract Self-assembly of dendrons allows a new approach for size control of bimetallic Pd–Pt nanoparticles, which affords reusable dendritic nanoreactors for selective hydrogenation of dienes and alkynes to monoenes in thermomorphic systems.

Supramolecular Catalysts by Encapsulating Palladium Complexes within Dendrimers.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Closer to the "ideal recoverable catalyst" for atom transfer radical polymerization using a molecular non-fluorous thermomorphic system.

The tetramine ligand 1 hexasubstituted by very long alkyl chains (C18H37) exhibits an exceptionally large temperature-dependent solubility in 1,4-dioxane, its solubility increasing ca. approximately 104-fold between 23 and 50 degrees C. The preformed copper(I) complex CuBr/1 was shown to catalyze the atom transfer radical polymerization of methyl methacrylate with good control of the molar masses and polydispersities. Due to the thermoresponsive character of CuBr/1 polymerizations were carried out in homogeneous conditions while lowering the temperature to 10 degrees C led to the precipitation of the catalyst. Catalyst recovery was achieved with high yield ( approximately 95%) by a simple filtration under noninert atmosphere. Very low residual copper contamination ( approximately 200 ppm) was measured in the final polymer. The catalyst was recycled two times without significant loss of activity.

Supramolecular catalysts by encapsulating palladium complexes within dendrimers.

Dendrimers are well-defined and highly branched macromolecules. By utilizing their capsular architectures, dendrimers encapsulating various catalytically active species can be prepared, which often bring about unique catalysis. Treatment of the alkylated PPI dendrimer with 4-diphenylphosphinobenzoic acid and [PdCl(C3H5)]2 afforded the dendrimer-encapsulated Pd complex using ionic interactions. The dendrimers encapsulating Pd complexes acted as unique supramolecular catalysts for the Heck reaction and allylic amination. The specific nanoenvironment created by the dense amino groups inside the dendrimers can provide high catalytic activity and stability for the Pd complexes. Facile recovery of the dendritic catalysts could be achieved by thermomorphic systems.

Microwave promoted Heck reactions using an oligo(ethylene glycol)-bound SCS palladacycle under thermomorphic conditions

Palladium catalyzed Heck couplings utilizing an air-stable, water-soluble oligo(ethylene glycol)-bound SCS palladacycle catalyst and microwave irradiation lead to formation of several cinnamic acid derivatives with reaction times of less than 1 hour. Such couplings of various aryl halides with alkene acceptors occur in an air atmosphere with aqueous and organic solvents are described. Recycling of the catalyst was accomplished using a 10% aqueous DMA–heptane thermomorphic system that was advantageously homogeneous during these microwave promoted reactions and biphasic during the catalyst recovery step.