Search results for " Liquid"

Eco-friendly functionalization of natural halloysite clay nanotube with ionic liquids by microwave irradiation for Suzuki coupling reaction

2014

Abstract Microwave assisted halloysite (HNT) external surface functionalization with ionic liquids is described. HNTs modification was achieved in two steps: a) grafting of 3-mercaptopropyl trimethoxysilane on the external surface of HNT by a microwave irradiation; b) anchorage of vinylimidazolium ionic liquids by a thiol-ene reaction. MW irradiation allowed us to obtain high loading onto the HNT surface compared to those obtained through conventional synthesis. Fourier transform infrared spectroscopy and thermogravimetric analysis confirmed that the grafting has occurred only on the external surface of HNT. Turbidimetric and dynamic light scattering analyses showed that the introduction of…

Heterogeneous oxidation of pyrimidine and alkyl thioethers in ionic liquids over mesoporous Ti or Ti/Ge catalysts.

2004

Heterogeneous catalytic oxidation of a series of thioethers (2-thiomethylpyrimidine, 2-thiomethyl-4,6-dimethyl-pyrimidine, 2-thiobenzylpyrimidine, 2-thiobenzyl-4,6-dimethylpyrimidine, thioanisole, and n-heptyl methyl sulfide) was performed in ionic liquids by using MCM-41 and UVM-type mesoporous catalysts containing Ti, or Ti and Ge. A range of triflate, tetrafluoroborate, trifluoroacetate, lactate and bis(trifluoromethanesulfonyl)-imide-based ionic liquids were used. The oxidations were carried out by using anhydrous hydrogen peroxide or the urea-hydrogen peroxide adduct and showed that ionic liquids are very effective solvents, achieving greater reactivity and selectivity than reactions p…

A counterion study of a series of [Cu(P^P)(N^N)][A] compounds with bis(phosphane) and 6-methyl and 6,6′-dimethyl-substituted 2,2′-bipyridine ligands …

2021

The syntheses and characterisations of a series of heteroleptic copper(i) compounds [Cu(POP)(Mebpy)][A], [Cu(POP)(Me2bpy)][A], [Cu(xantphos)(Mebpy)][A] and [Cu(xantphos)(Me2bpy)][A] in which [A]− is [BF4]−, [PF6]−, [BPh4]− and [BArF4]− (Mebpy = 6-methyl-2,2′-bipyridine, Me2bpy = 6,6′-dimethyl-2,2′-bipyridine, POP = oxydi(2,1-phenylene)bis(diphenylphosphane), xantphos = (9,9-dimethyl-9H-xanthene-4,5-diyl)bis(diphenylphosphane), [BArF4]− = tetrakis(3,5-bis(trifluoromethyl)phenyl)borate) are reported. Nine of the compounds have been characterised by single crystal X-ray crystallography, and the consequences of the different anions on the packing interactions in the solid state are discussed. T…

1979

Pressure influences on the viscosity of polymer solutions

1982

Of all physico-chemical quantities characterizing the behavior of liquids, the viscosity coefficient η is normally most sensitive to pressure. Early measurements of η(p) date back almost 100 years [1] but they were carried out with very different objectives [2]. Currently, one is particularly interested in polymer solutions, for instance because of the additives to motor oils and of oil recovery. The present paper reports on measurements with polystyrenes of high molecular uniformity in eight different solvents. It confines itself to zero-shear viscosities and discusses the possibilities of discovering the influence of pressure via the molecular structure of the solvent and via its thermody…

Factors influencing the transport of tryptophan hydrochloride through supported liquid membranes containing macrocyclic carriers

1997

Commercially available PTFE membranes were used as a support for liquid membranes in amino acid transport. Using tryptophan as a model amino acid, the influence of the type of organic liquid, kind of macrocyclic carrier and counter-ion on transport efficiency was examined. These studies show the strong influence of the kind of the counter-ion co-transported with amino acid cation, and the type of macrocyclic carrier used on the transport efficiency. The transport efficiency depends also on the pH of the source phase and on the nature of the organic liquid used as a membrane solvent. Liquid membranes supported on commercial porous-PTFE-membranes with hydrophobic solvents are stable for more …

Supported liquid membrane separation of amine and amino acid derivatives with chiral esters of phosphoric acids as carriers

2003

Studies on the possible use of phosphate and phosphonate esters bearing chiral menthol or nopol moieties as carriers for the transport of amines, amino acids, and amino acid esters through supported liquid membranes (SLM) are presented. Additionally, the enantioselectivity of the SLM transport of alkyl esters of aromatic amino acids and a non‐protein amino acid was also evaluated. It could be concluded that the extent of transport strongly depends on the hydrophobicity of the amino compound. Moreover, the carrier structure also influences the transport of those compounds through SLM: chiral phosphate and phosphonate esters appear to be poor or moderate carriers for enantioselective SLM tran…

Concentration of amino acids using supported liquid membranes with di-2-ethylhexyl phosphoric acid as a carrier

1997

Abstract Basic studies of a procedure for extraction of amino acids using a supported liquid membrane containing di-2-ethylhexyl phosphoric acid are presented. The extractions are made from an aqueous donor phase with pH 3 to a more acidic acceptor phase and the mass transfer is driven by the proton gradient between these phases. For 0.01 mM tryptophan and with 1 M HCl as acceptor phase, an extraction efficiency of 60% is obtained, constant up to at least 12 h. This permits concentration enrichment factors linearly increasing with time up to values of at least 150. For higher amino acid concentrations, the extraction efficiency is constant only over shorter time intervals.

ChemInform Abstract: Convenient High Yielding Gram Scale Solution Synthesis of Methionine-Enkephalin.

2010

A simple, large-scale synthesis of a cytokine, methionine-enkephalin, Tyr-Gly-Gly-Phe-Met, has been elaborated. Classical solution peptide chemistry methods without protection of amino acid side-chain functions and 1+(2+2) segment condensation were used. A nine-step synthesis from commercial amino acid derivatives was developed with yields ranging from 86% to 99%, averaging 92%. The purity of all intermediates was found to be 99.0-100% by HPLC. The process has been used to prepare greater than 150 g quantities of the pentapeptide as a monohydrate of 100% purity. Hydantoin formation was observed during saponification of Boc-Tyr-Gly-Gly-Phe-Met-OMe and minimised.

Convenient High Yielding Gram Scale Solution Synthesis of Methionine-Enkephalin.

1998

A simple, large-scale synthesis of a cytokine, methionine-enkephalin, Tyr-Gly-Gly-Phe-Met, has been elaborated. Classical solution peptide chemistry methods without protection of amino acid side-chain functions and 1+(2+2) segment condensation were used. A nine-step synthesis from commercial amino acid derivatives was developed with yields ranging from 86% to 99%, averaging 92%. The purity of all intermediates was found to be 99.0-100% by HPLC. The process has been used to prepare greater than 150 g quantities of the pentapeptide as a monohydrate of 100% purity. Hydantoin formation was observed during saponification of Boc-Tyr-Gly-Gly-Phe-Met-OMe and minimised.