Search results for "ionic"
showing 10 items of 2016 documents
Über die elementarprozesse bei der anionischen polymerisation des styrols in tetrahydropyran (THP)
1972
Kinetische und konduktometrische Messungen am System Polystyrl-Natrium in THP werden mit dem Ziel durchgefuhrt, alle in dem fruher vorgeschlagenen dreiteiligen Reaktionsschema vorkommenden thermodynamischen und kinetischen Parameter zu bestimmen und mit den in anderen Losungsmitteln gefundenen Werten zu vergleichen. Es zeigt sich, das die Geschwindigkeitskonstanten der Monomeraddition an das Kontaktionenpaar, das solvatgetrennte Ionenpaar und das freie Anion, die sich um Grosenordnungen unterscheiden, vom Losungsmittel nur geringfugig beeinflust werden. Der ungewohnlich grose Einflus der Losungsmittel auf die Polymerisationsgeschwindigkeit geschieht durch Verschiebung der Gleichgewichte zwi…
The kinetics of anionic polymerization of styrene in 1,2-dimethoxiethane
2007
Kinetic measurements in a flow apparatus in combination with conductance measurements, permit the determination of the two equilibrium constants Kes and Kdiss* and the three propagation rate constants k(±)c, k(±)s and k(−) as a function of temperature. The great differences in the polymerization rate in various solvents are mainly caused by their influence on the equilibrium constants. The influence of the solvent on the rate constants is not greater than in other chemical reactions.
On the ionizing properties of supercritical carbon dioxide: uncatalyzed electrophilic bromination of aromatics
2014
Supercritical carbon dioxide (scCO2), a solvent with a zero dipole moment, low dielectric constant, and no hydrogen bonding behavior, is a suitable medium to perform the uncatalyzed electrophilic bromination of weakly activated aromatics with no interference of radical pathways. The ability of scCO2 to promote these reactions matches those of strongly ionizing solvents such as aqueous acetic and trifluoroacetic acids. Conversely, carbon tetrachloride, with similar polarity parameters to scCO2, leads exclusively to side chain functionalization. The strong quadrupole moment, and the acidic, but non basic, Lewis character of carbon dioxide, are proposed as key factors for the singular performa…
Die kationische polymerisation von monomerem formaldehyd in lösung. 39. Mitt. über polyoxymethylene
1971
Die kationische Polymerisation (Fallungspolymerisation) von monomerem Formaldehyd wird in verschiedenen organischen Losungsmitteln bei −78 bis −30°C untersucht; sie ist bezuglich der Initiator- und Monomerkonzentration jeweils erster Ordnung. Die Wirksamkeit der Initiatoren fur die Polymerisation in Toluol bei −78°C nimmt in der Reihenfolge ab: SnCl4 > CH3COClO4 > HClO4 > AlBr3 > BF3 ċ O(C2H5)2 > TiCl4 > FeCl3 > SbCl5 > H2SO4 > Cl3CCOOH > HCOOH > Jod. Die Bruttoaktivierungsenergien betragen 1,0 bis 10 kcal/Mol. Die Polymerisationsgrade (Viskositatsmittel Pv) steigen meist etwa proportional mit der Monomerkonzentration und dem Umsatz an und erreichen Werte bis Pv ∼ 15000. Bei Variation des L…
Influence of Some Ionic Liquids Containing the Trifluoromethanesulfonate Anion on the Vapor–Liquid Equilibria of the Acetone + Methanol System
2011
Isobaric vapor–liquid equilibria (VLE) for the binary systems acetone + 1-butyl-3-ethylimidazolium trifluoromethanesulfonate ([beim][triflate]), methanol + [beim][triflate], acetone + 1-butyl-1-methylpyrrolidinium trifluoromethanesulfonate ([bmpyr][triflate]), and methanol + [bmpyr][triflate] as well as the VLE for the acetone + methanol + [beim][triflate] and acetone + methanol + [bmpyr][triflate] ternary systems have been obtained at 100 kPa using a recirculating still. The addition of both ionic liquids to the solvent mixtures produced an important salting-out effect, and the azeotrope tended to disappear for small amounts of ionic liquid. The experimental binary data sets were independe…
Isolation of human milk whey proteins by solid phase extraction with a polymeric material modified with gold nanoparticles
2017
Abstract This work describes a method for the isolation of human milk whey proteins by solid-phase extraction (SPE) with a polymeric material modified with gold nanoparticles. Human serum albumin, α-lactalbumin, lactoferrin and lysozyme were selected as target proteins to establish the performance of SPE support. Several experimental variables (pH and ionic strength) that affect the SPE protocol were investigated to achieve the maximum extraction efficiency. Under optimal conditions, the SPE sorbent gave excellent recoveries, and offered a high permeability and reusability (> 20 times). The feasibility of this methodology was successfully demonstrated by isolating the target proteins in a m…
Methylone determination in oral fluid using microextraction by packed sorbent coupled to ion mobility spectrometry
2020
Abstract A methodology based on microextraction by packed sorbent (MEPS) followed by ion mobility spectrometry (IMS) has been developed for the simple and automated determination of methylone in oral fluids. MEPS was carried out using a 100 µL eVol® XR hand-held automated analytical syringe filled with octadecyl silica sorbent. The effect of main experimental parameters of MEPS such as sample pH and ionic strength, number of aspirating/dispensing cycles, and elution solvent was studied to obtain a quantitative extraction of methylone. Oral fluid samples were spiked with methylone at different concentration levels from 50 to 400 µg L−1 and analyzed by the proposed MEPS-IMS procedure, giving …
Porous Coordination Polymer Based on Bipyridinium Carboxylate Linkers with High and Reversible Ammonia Uptake
2016
The zwitterionic bipyridinium carboxylate ligand 1,1'-bis(4-carboxyphenyl)-4,4'-bipyridinium (pc1) in the presence of cadmium chloride affords novel porous coordination polymers (PCPs): [Cd4(pc1)3Cl6]·CdCl4·guest (1) crystallizing in the P3̅1c space group. In the structure, [Cd4Cl6(CO2)6] building units are linked together by six pc1 ligands, leading to a 3D high-symmetrical network exhibiting hexagonal channels along the c axis. The walls of this PCP consist of cationic electron-acceptor bipyridinium units. The PCP 1 reversibly adsorbs H2O and CH3OH up to about 0.1 g/g at saturation showing the adsorption isotherms characteristic of a moderately hydrophilic sorbent. Adsorption of ammonia (…
A novel peat-based biosorbent for the removal of phosphate from synthetic and real wastewater and possible utilization of spent sorbent in land appli…
2015
AbstractRemoval of potentially harmful phosphorus compounds from wastewater by adsorption onto biosorbents is a cost-effective alternative to the conventional treatment methods. Raw peat and peat modified with iron(III) hydroxy ions were used in this study to remove phosphate ions from synthetic solution and household wastewater. Interaction of iron(III) ions with carboxylic groups of peat occurred during peat modification, which was confirmed by the FTIR technique. The effect of the initial phosphate concentration, pH, contact time, temperature, and ionic strength was studied in batch experiments. It was found that the sorption capacity increased with the increasing temperature, i.e. the m…
Carbon Nanomaterial Doped Ionic Liquid Gels for the Removal of Pharmaceutically Active Compounds from Water.
2019
Due to large drug consumption, pharmaceutically active compounds (PhACs) can be found as water contaminants. The removal of PhACs is a significant issue, as they can easily overtake traditional purification methods. Because of their surface properties, carbon nanomaterials are among the most efficient materials able to adsorb PhACs. However, their limitation is their recovery after use and their possible leakage into the aquatic system. Consequently, new hybrid supramolecular ionic liquid gels (HILGs) have been designed for the adsorption of some antibiotic drugs (ciprofloxacin and nalidixic acid) from water. The chemical&ndash