Thermodynamics of Adsorption in a Cellulose–Water System

Russian Journal of Physical Chemistry A - The sorption properties of native cellulose and the state of water adsorbed by its fibers are studied by measuring 1H NMR relaxation. A scheme of the...     

Effect of Pressure on Clathrate Formation in a Water–Ethanol System

The water–ethanol (E) system was studied by differential thermal analysis (DTA) at atmospheric pressure and pressures up to 10 kbar. At atmospheric pressure, the system was shown to contain an incongruently melting hydrate of E · 2H₂O composition (t_decomp = -65.0°C). In addition, the system involves two metastable hydrates: E · 3H₂O (t_decomp = -69.0°C) and E · 4.75H₂O t_decomp = -74.5°C)}. The hydrate compositions were determined by Tamman's method for the corresponding temperature invariants. Studies at pressures below 10 kbar showed that E · 4.75H₂O metastable hydrate becomes stable at pressures above 0.25 kbar. At pressures from 1.0 to 7.3 kbar, this hydrate melts congruently, which allowed its composition to be determined more accurately. Presumably, this hydrate is of a semiclathrate nature (i.e., the ethanol molecule is involved in constructing the water framework) and has cubic structure I. In experiments at high pressures, E · 3H₂O was not found. Concerning E · 2H₂O hydrate, its peritectic melting was observed up to 5.0 kbar. Further extrapolation extends the incongruent melting curve to 7.5 kbar.     

Spectrophotometric Determination of Copper in Waste Water Using Liquid–Liquid Extraction in a Flow-Injection System

A flow-injection procedure for the determination of copper in waste water is described. The procedure is based on the formation of an ion-pair between tetrabutylammonium and the tetrathiocyanatocuprate(II) anion. This ion-pair is extracted with chloroform, and the absorbance of the organic phase is measured at 485nm. Concentrations of copper 0.4mg L^–1 can be detected with a linear application range of between 0.5 and 25mg L^–1, a relative standard deviation of 2.3% (0.8mg L^–1, n=10) and a sampling frequency of 30h^–1. Under the proposed working conditions, only Ni(II) and Pd(II) interfere at molar ratios Ni(II)/Cu(II) 50 and Pd(II)/Cu(II) 100.     

Determination of Iron in Tap and Waste Water Using Liquid–Liquid Extraction in a Flow-Injection System

A flow-injection procedure for the determination of iron(III) in water is described. The procedure is based on the formation of an ion pair between the tetraphenylarsonium (Ph₄As⁺) (TPA) or tetrabutylammonium (But₄N⁺) (TBA) cations and the tetrathiocyanatoferrate(III) complex (TTF). This ion pair is extracted with chloroform, and the absorbance of the organic phase is measured at 503nm (for Ph₄As⁺) or 475nm (for But₄N⁺). Iron concentrations higher than 0.9×10^–6molL^–1 (50µgL^–1) can be detected in the first case, with a relative standard deviation of 1.9% (n=12), a linear application rangeof between 1.34 and 54.0×10^–6molL^–1 (75–3015µgL^–1), and a sampling frequency of 30h^–1. For the ion pair with But₄N⁺, the detection limit is 0.52×10^–6molL^–1 (29µgL^–1), with a relative standard deviation of 1.6% and a linear application range between 0.73 and 54.0×10^–6molL^–1. Under the proposed working conditions, only Pd(IV), Cu(II) and Bi(III) interfere. With the application of the merging zones technique, considerable amounts of organic reagent can be saved. The TBA method was applied to the analysis of iron(III) in tap and industrial waste waters.     

A Mild and Efficient Oxidation of Alcohols in Water

A mild and efficient oxidation of alcohols to the corresponding carbonyl compounds using the PhI(OAc)2 (1.1 eq.) with n-Bu4NBr (8 mol %) in water at room temperature is described.This new procedure is very simple and affords the desired carbonyl compounds in high yields.     

Efficient Synthesis of bis- and tris-Indolylalkanes Catalyzed by a Brønsted Acid–Surfactant Catalyst in Water

A simple and efficient synthesis of bis- and tris-indolylalkanes from carbonyls (aldehydes/ketones) and indoles with excellent yields in the presence of dodecylsulphonic acid (DSA) in water at room temperature is described. The catalyst is also applicable for the synthesis of 3,3-di(3-indolyl)oxindoles. The dodecylsulphonic acid acts as both Brønsted acid and surface-active agent in the reaction mixture.     

Highly Efficient Synthesis of 3,5-Diaryl-1,2,4-thiadiazoles in Water–Wet Paste Conditions

1,3-Dibromo-5,5-diphenylimidazolidine-2,4-dione (N,N’-dibromo phenytoin) was efficiently used for the rapid conversion of thiobenzamides to the corresponding 3,5-diaryl-1,2,4-thiadiazoles in water–wet paste conditions.

Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications® to view the free supplemental file.

Iodine-Catalyzed,Efficient Synthesis of α-Hydroxy Phosphonates in Water

An efficient and simple synthesis of α-hydroxy phosphonates from aldehydes and triethylphosphite in the presence of iodine in water has been developed. Environmentally benign reaction conditions, high yield, and easily available catalyst are important features of this method.

Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.     

Electrochemical Hydrogenation of Acetophenone and Methyl-4-isobutylacetophenone in a Two-phase Water–Organic System Containing β-Cyclodextrin

The possibility of the formation of inclusion complexes based on methyl-4-isobutylphenyl ketone, -cyclodextrin (-CD), and o-hydroxy propylated -cyclodextrin in an aqueous phosphate buffer is demonstrated by methods of NMR spectroscopy and cyclic voltammetry. Preparative electroreduction of acetophenone and methyl-4-isobutylphenyl ketone is performed on a lead electrode in aqueous phosphate and acetate buffers in the absence and presence of -CD and the composition of products of electrochemical reactions is ascertained. It is shown that the products of reduction of ketones are corresponding alcohols and pinacones. The possibility of asymmetric electrochemical hydrogenation of ketones in the presence of -CD, which yields relevant chiral alcohols, is shown.     

Breakdown of the Rule of “Linearity of Water Isoactivity Lines” in a System Containing Solid Solutions

Osmotic coefficients of water have been measured isopiestically for the entire region of homogeneous ternary solutions for the Rb₂SO₄- (NH₄)₂SO₄-H₂O system at 25°C. One might expect that water isoactivity lines should be straight since this system involves a continuous series of solid solutions. The related systems (K₂SO₄-Rb₂SO₄-H₂O and (K₂SO₄- (NH₄)₂ SO₄-H₂O) obey the linearity of water isoactivity lines rule. Contrary to expectations, the (Rb₂SO₄-(NH₄)₂-SO₄-H₂O appears to be the first water–salt system containing continuous solid solutions in which the mentioned rule is not obeyed.     

Enhanced Dibenzothiophene Biodesulfurization by Immobilized Cells of Brevibacterium lutescens in n-Octane–Water Biphasic System

In this study, it was the first report that the Brevibacterium lutescens CCZU12-1 was employed as a sulfur removing bacteria. Using dibenzothiophene (DBT) as the sole sulfur source, B. lutescens could selectively degrade DBT into 2-hydroxybiphenyl (2-HBP) via the “4S” pathway. In the basal salt medium (BSM) supplemented with 0.25 mM DBT and 0.5 g/L Tween-80, high desulfurization rate (100 %) was obtained by growth cells after 60 h. Furthermore, the n-octane–water (10:90, v/v) biphasic system was built for the biodesulfurization by resting cells. Moreover, a combination of magnetic nano Fe₃O₄ particles with calcium alginate immobilization was used for enhancing biodesulfurization. In this n-octane–water biphasic system, immobilized B. lutescens cells could be reused for not less than four times. Therefore, B. lutescens CCZU12-1 shows high potential in the biodesulfurization.     

Efficient Regioselective Ring Opening of Oxiranes with Thioacids in the Presence of β‐Cyclodextrin in Water

A mild and convenient synthesis of β‐hydroxy thioesters has been achieved by the regioselective ring opening of oxiranes using thioacetic acid and thiobenzoic acid in the presence of β‐cyclodextrin in water at room temperature. β‐Hydroxy thioesters are realized in high yields, and β‐cyclodextrin can also be recovered and reused.     

Diffusion Properties of the Ternary System Human Serum Albumin–Sodium Cholate–Water

The four diffusion coefficients of the ternary system human serum albumin (HSA,1)–sodium cholate (NaC,2)–water (W,0) were determined at three average compositions with constant protein concentration, C ₁ ^o , and variable bile salt concentration, C ₂. Various types of solute–solute interactions are present in this ternary system: electrostatic, co-ions–protein, and unspecific volume interactions due to the large difference in size of the two solutes. Each type of interaction has a different effect in determining the values and the sign of the experimental diffusion coefficients, ^exp D _ij . To simplify the analysis of the dependence of the ^exp D _ij s on C ₂, we considered three model systems where different types of solute–solute interaction are present individually. The overall analysis allows highlighting which kinds of solute–solute interaction predominates in determining the value of each diffusion coefficient.     

Structural Inhomogeneity in Electrolyte Solutions: The Calcium Perchlorate–Water System

A new approach has been proposed to study the structure of aqueous electrolyte solutions. NIR, Raman and attenuated total reflectance, Fourier transform infra-red (ATR FTIR) spectra have been measured for aqueous calcium perchlorate solutions in the 0.22–4.3 mol·L^?1 (0.22–7.46 mol·kg^?1) concentration range at 25 °C. By the methods of principal component analysis (PCA) and multivariate curve resolution—alternating least squares (MCR-ALS) the number, spectra and concentration profiles have been determined for spectroscopically distinguishable forms of water and ClO ₄ ^? ion in solutions. The results have been analyzed using a phenomenological model, establishing thereby: concentration ranges for structural rearrangements of the solution, the nature of structural microirregularities and different states of the ClO ₄ ^? ion in the areas of domination of the natural water structure, and of cybotactic groups of calcium perchlorate hexa and tetra hydrates.     

Synthesis and Characterization Performance of Amphiphilic ZnO,a Novel Photocatalyst Suitable for Degradation of Contaminants in Oil–Water Two Phase System

Russian Journal of Physical Chemistry A - Amphiphilic zinc oxide (ZnO) was successfully prepared by modifing neat ZnO with silane coupling reagent KH-570. The modified ZnO and neat ZnO were...     

Catalytic Dechlorination of Chlorobenzene in Water by Pd／Fe System

Chlorobenzene was dechlorinated by Pd/Fe bimetallic system in water through catalytic reduction. The dechlorination rate increases with increase of bulk loading of Pd due to the increase of both the surface loading of the Pd and the total surface area. For conditions with 0.005% Pd/Fe, 45% dechlorination efficiency was achieved within 5 h. The dechlorinated reaction is believed to take place on the bimetal surface in a pseudo-first-order reaction, with the rate constant being 0.0043 min^-1.     

CuI/PPh3/PEG–Water: An Efficient Catalytic System for Cross-Coupling Reaction of Aryl Iodides and Alkynes

An efficient protocol for the copper-catalyzed Sonogashira coupling of aryl iodides with terminal acetylenes in water–polyethylene glycol has been established. Both electron-rich and electron-deficient aryl iodides were arylalkynated under microwave heating or reflux in oil bath to afford good to excellent yields.