Synthesis of highly substituted pyrrolidines via palladium-catalyzed cyclization of 5-vinyloxazolidinones and activated alkenes

N-Tosyl-5,5-divinyloxazolidin-2-one undergoes a palladium-catalyzed decarboxylative cyclization across a range of electrophilic alkenes to give the corresponding pyrrolidine derivatives bearing two contiguous quaternary centres. Alkenes bearing two electron-withdrawing groups are required; pyrrolidines were not formed from mono-activated alkenes. Bulky, electron-rich phosphines promote pyrrolidine formation with less highly electrophilic, doubly activated alkenes, and a dramatic improvement is observed in the presence of iodide.

Temperature-Driven Mixing-Demixing Behavior of Binary Mixtures of the Ionic Liquid Choline Bis(trifluoromethylsulfonyl)imide and Water

The ionic liquid (2-hydroxyethylammonium)trimethylammonium) bis(trifluoromethylsulfonyl)imide (choline bistriflimide) was obtained as a supercooled liquid at room temperature (melting point = 30 degrees C). Crystals of choline bistriflimide suitable for structure determination were grown from the melt in situ on the X-ray diffractometer. The choline cation adopts a folded conformation, whereas the bistriflimide anion exhibits a transoid conformation. The choline cation and the bistriflimide anion are held together by hydrogen bonds between the hydroxyl proton and a sulfonyl oxygen atom. This hydrogen bonding is of importance for the temperature-dependent solubility proper-ties of the ionic liquid. Choline bistriflimide is not miscible with water at room temperature, but forms one phase with water at temperatures above 72 degrees C (equals upper critical solution temperature). H-1 NMR studies show that the hydrogen bonds between the choline cation and the bistriflimide anion are substantially weakened above this temperature. The thermophysical properties of water-choline bistriflimide binary mixtures were furthermore studied by a photopyroelectric technique and by adiabatic scanning calorimetry (ASC). By photothermal analysis, besides highly accurate values for the thermal conductivity and effusivity of choline bistriflimide at 30 degrees C, the detailed temperature dependence of both the thermal conductivity and effusivity of the upper and lower part of a critical water-choline bistriflimide mixture in the neighborhood of the mixing-demixing phase transition could be determined with high resolution and accuracy. Together with high resolution ASC data for the heat capacity, experimental values were obtained for the critical exponents alpha and beta, and for the critical amplitude ratio G(+)/G(-). These three values were found to be consistent with theoretical expectations for a three dimensional Ising-type of critical behavior of binary liquid mixtures.

Visible and Near-Infrared Emission by Samarium(III)-Containing Ionic Liquid Mixtures

Highly luminescent anionic samarium(III) beta-diketonate and dipicolinate complexes were dissolved in the imidazolium ionic liquid 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [C(6)mim][Tf2N]. The solubility of the complexes in the ionic liquid was ensured by a careful choice of the countercation of the samarium(III) complex. The samarium(III) complexes that were considered are [C(6)mim][SM(tta)(4)], where tta is 2-thenoyltrifluoroacetonate; [C(6)mim][Sm(nta)(4)], where nta is 2-naphthoyltrifluoroacetonate; [C(6)mim][Sm(hfa)(4)], where hfa is hexafluoroacetylacetonate; and [choline](3)-[Sm(dpa)(3)], where dpa is pyridine-2,6-dicarboxylate (dipicolinate) and [choline](+) is (2-hydroxyethyl)trimethyl ammonium. The crystal structures of the tetrakis samarium(III) P-diketonate complexes revealed a distorted square antiprismatic coordination for the samarium(III) ion in all three cases. Luminescence spectra were recorded for the samarium(III) complexes dissolved in the imidazolium ionic liquid as well as in a conventional solvent, that is, acetonitrile or water for the beta-diketonate and dipicolinate complexes, respectively. These experiments demonstrate that [C(6)mim][Tf2N] is a suitable spectroscopic solvent for studying samarium(III) luminescence. High-luminescence quantum yields were observed for the samarium(III) beta-diketonate complexes in solution.

Adsorption of methylene blue onto activated carbon produced from steam activated bituminous coal: A study of equilibrium adsorption isotherm.

Chemical Engineering Journal, 124 (2006) 103.

Adsorption of basic dyes from aqueous solution onto activated carbons

The aim of this research is to compare the adsorption capacity of different types of activated carbons produced by steam activation in small laboratory scale and large industrial scale processes. Equilibrium behaviour of the activated carbons was investigated by performing batch adsorption experiments using bottle-point method. Basic dyes (methylene blue (MB), basic red (BR) and basic yellow (BY)) were used as adsorbates and the maximum adsorptive capacity was determined. Adsorption isotherm models, Langmuir, Freundlich and Redlich-Peterson were used to simulate the equilibrium data at different experimental parameters (pH and adsorbent particle size). It was found that PAC2 (activated carbon produced from New Zealand coal using steam activation) has the highest adsorptive capacity towards MB dye (588 mg/g) followed by F400 (476 mg/g) and PAC 1 (380 mg/g). BR and BY showed higher adsorptive affinity towards PAC2 and F400 than MB. Under comparable conditions, adsorption capacity of basic dyes, MB, BR and BY onto PAC 1, PAC2 and F400 increased in the order: MB <BR <BY. Redlich-Peterson model was found to describe the experimental data over the entire range of concentration under investigation. All the systems show favourable adsorption of the basic dyes with 0 <R-L <I (C) 2007 Elsevier B.V. All rights reserved.

Effect of solution pH, ionic strength, and temperature on adsorption behavior of reactive dyes on activated carbon

The adsorption behavior of C.I. Reactive Blue 2, C.I. Reactive Red 4, and C.I. Reactive Yellow 2 from aqueous solution onto activated carbon was investigated under various experimental conditions. The adsorption capacity of activated carbon for reactive dyes was found to be relatively high. At pH 7.0 and 298 K, the maximum adsorption capacity for C.I. Reactive Blue 2, C.I. Reactive Yellow 2 and C.I. Reactive Red 4 dyes was found to be 0.27, 0.24, and 0.11 mmol/g, respectively. The shape of the adsorption isotherms indicated an L2-type isotherm according to the Giles and Smith classification. The experimental adsorption data showed good correlation with the Langmuir and Ferundlich isotherm models. Further analysis indicated that the formation of a complete monolayer was not achieved, with the fraction of surface coverage found to be 0.45, 0.42, and 0.22 for C.I. Reactive Blue 2, C.I. Reactive Yellow 2 and C.I. Reactive Red 4 dyes, respectively. Experimental data indicated that the adsorption capacity of activated carbon for the dyes was higher in acidic rather than in basic solutions, and further indicated that the removal of dye increased with increase in the ionic strength of solution, this was attributed to aggregation of reactive dyes in solution. Thermodynamic studies indicated that the adsorption of reactive dyes onto activated carbon was an endothermic process. The adsorption enthalpy (?H) for C.I. Reactive Blue 2 and C.I. Reactive Yellow 2 dyes were calculated at 42.2 and 36.2 kJ/mol, respectively. The negative values of free energy (?G) determined for these systems indicated that adsorption of reactive dyes was spontaneous at the temperatures under investigation (298-328 K). © 2007 Elsevier Ltd. All rights reserved.

Textile wastewater treatment using granular activated carbon adsorption in fixed beds

This work involved the treatment of industrial wastewater from a nylon carpet printing plant which currently receives no treatment and is discharged to sea. As nylon is particularly difficult to dye, acid dyes are required for successful coloration and cause major problems with the plant's effluent disposal in terms of color removal. Granular activated carbon Filtrasorb 400 was used to treat a ternary solution of acid dyes and the process plant effluent containing the dyes in a fixed-bed column system. Experimental data were correlated using the bed depth service time (BDST) model to previously published work by the authors for single dye adsorption. The results were expressed in terms of the BDST adsorption capacity, in milligrams of adsorbate per gram of adsorbent, and indicated that there was a 12-25% decrease iri adsorption capacity in the ternary system compared to the single component system; This reduction has been attributed to competitive adsorption occurring in the ternary component system. Dye adsorption from the process plant effluent showed an approximate 65% decrease in adsorption capacity compared to the ternary solution system. This has been attributed to interference caused by the other colorless textile effluent pollutants found in the process wastewater. A chemical oxygen demand analysis on these components indicated that the dyes accounted for only 14% of the total oxygen demand.

Prediction of bisolute dye adsorption isotherms on activated carbon

The removal of acid dyes, Tectilon Blue 4R, Tectilon Red 2B and Tectilon Orange 3G, from single solute, bisolute and trisolute solutions by adsorption on activated carbon (GAC F400) has been investigated in isotherm experiments. Results from these experiments were modelled using the Langmuir and Freundlich adsorption isotherm theories with the Langmuir model proving to be the more suitable. The Ideal Adsorbed Solution (IAS) model was coupled with the Langmuir isotherm to predict binary adsorption on the dyes. The application of the IAS theory accurately simulated the experimental data with an average deviation of approximately 3% between modelled and experimental data.

Solvent strength of ionic liquid/CO2 mixtures

Previously we have shown that organic solutes can be extracted from ionic liquids (ILs) with supercritical CO2 and that ILs can be induced to separate from organic and aqueous mixtures by applying gaseous CO2 pressure. Thus, we are interested in the solvent strength of IL/CO2 mixtures. Here we use 4-nitroaniline, N,N-diethyl-4-nitroaniline and Reichardt's dye 33 to determine the Kamlet-Taft parameters for four different imidazolium based ILs and their mixtures with CO2 at 25 and 40degreesC. The effect of temperature and carbon dioxide concentration on these parameters was determined. The polarizability parameter depends weakly on the CO2 concentration. However, the hydrogen bond donating ability and the hydrogen bond accepting ability are virtually independent Of CO2 pressure. The results indicate that the strong interactions between ILs and probe molecules are not influenced by CO2.

Artificial Intelligence Model for Flowable Concrete Mixtures Used in Underwater Construction and Repair

This study explores using artificial neural networks to predict the rheological and mechanical properties of underwater concrete (UWC) mixtures and to evaluate the sensitivity of such properties to variations in mixture ingredients. Artificial neural networks (ANN) mimic the structure and operation of biological neurons and have the unique ability of self-learning, mapping, and functional approximation. Details of the development of the proposed neural network model, its architecture, training, and validation are presented in this study. A database incorporating 175 UWC mixtures from nine different studies was developed to train and test the ANN model. The data are arranged in a patterned format. Each pattern contains an input vector that includes quantity values of the mixture variables influencing the behavior of UWC mixtures (that is, cement, silica fume, fly ash, slag, water, coarse and fine aggregates, and chemical admixtures) and a corresponding output vector that includes the rheological or mechanical property to be modeled. Results show that the ANN model thus developed is not only capable of accurately predicting the slump, slump-flow, washout resistance, and compressive strength of underwater concrete mixtures used in the training process, but it can also effectively predict the aforementioned properties for new mixtures designed within the practical range of the input parameters used in the training process with an absolute error of 4.6, 10.6, 10.6, and 4.4%, respectively.