Homogeneous liquid-liquid extraction of trace amounts of mononitrotoluenes from waste water samples

Homogeneous liquid-liquid extraction method was studied based on a phase separation phenomenon in a ternary solvent system. According to this procedure, mononitrotoloenes were extracted by single-phase extraction in a water/methanol/chloroform, homogeneous ternary solvent system. Methanol and chloroform were used as consolute and extraction solvents, respectively. The homogeneous solution was broken by the addition of salt and a cloudy solution was formed. After centrifugation, the fine droplets of the extraction solvent were sedimented in the bottom of the conical test tube. Analysis of the extracts was carried out by gas chromatography. The optimization procedure was performed using Box-Behnken design. The variables involved were: sample and extraction solvent volumes, consolute solvent volume and phase separator reagent concentration. Optimum results were obtained under the following conditions: sample volume of 5 mL, extraction solvent volume of 55 μL, consolute solvent volume of 1 mL and phase separator reagent concentration; 5% (w/v). Under these conditions, the enrichment factors of 354, 311 and 300, dynamic linear ranges of 0.5-500, 1-500 and 1-500 μg L⁻¹, and limit of detections (LODs) of 0.09, 0.09 and 0.1 μg L⁻¹ were obtained for o-nitrotoluene, m-nitrotoluene and p-nitrotoluene, respectively. Finally, the method was successfully applied to the extraction and determination of MNTs in the waste water samples in the range of micrograms per liter with R.S.Ds. < 13.2%.     

Two single‐enantiomer amidophosphoesters: a database study on the chirality of (O)2P(O)(N)‐based structures

The crystal structures of two single‐enantiomer amidophosphoesters with an (O)₂P(O)(N) skeleton, i.e. diphenyl [(R)‐(+)‐α‐methylbenzylamido]phosphate, (I), and diphenyl [(S)‐(?)‐α‐methylbenzylamido]phosphate, (II), both C₂₀H₂₀NO₃P, are reported. In both structures, chiral one‐dimensional hydrogen‐bonded architectures, along [010], are mediated by N—H…OP interactions. The statistically identical assemblies include the noncentrosymmetric graph‐set motif C(4) and the compounds crystallize in the chiral space group P2₁. As a result of synergistic co‐operation from C—H…O interactions, a two‐dimensional superstructure is built including a noncentrosymmetric R₄⁴(22) hydrogen‐bonded motif. A Cambridge Structural Database survey was performed on (O)₂P(O)(N)‐based structures in order to review the frequency of space groups observed in this family of compounds; the hydrogen‐bond motifs in structures with chiral space groups and the types of groups inducing chirality are discussed. The ^2,3J_X–P (X = H or C) coupling constants from the NMR spectra of (I) and (II) have been studied. In each compound, the two diastereotopic C₆H₅O groups are different, which is reflected in the different chemical shifts and some coupling constants.     

The effect of probe-Ohmic environment coupling type and probe information flow on quantum probing of the cutoff frequency

This work aims to compare results of dissipating and pure dephasing single-qubit probes in characterizing the cutoff frequency of a harmonic reservoir Ohmic spectral density. In particular, we proved that a dissipating single-qubit improves the estimation precision of the cutoff frequency estimator. The information backflow and outflow of the dissipating and the dephasing single-qubit are compared. The relation between the quantum Fisher information and the information outflow and backflow of the probe is obtained. The results show that difference between the values of information outflow and backflow of a dissipating single-qubit is larger than a dephasing single-qubit. So, a single-qubit probe extracts more information from an Ohmic reservoir by increasing the difference between the values of information outflow and backflow of the probe.     

An optimization method based on the generalized polynomials for nonlinear variable-order time fractional diffusion-wave equation

In this paper, an optimization method based on a new class of basis functions, namely generalized polynomials (GPs), is proposed for nonlinear variable-order time fractional diffusion-wave equation. Variable-order time fractional derivative is expressed in the Caputo sense. In the proposed method, solution of the problem under consideration is expanded in terms of GPs with unknown free coefficients and control parameters. In this way, some new operational matrices of the ordinary and fractional derivatives are derived for these basis functions. The residual function and its 2-norm are employed for converting the problem under study to an optimization one and then choosing the unknown free coefficients and control parameters optimally. As a useful result, the necessary conditions of optimality are derived as a system of nonlinear algebraic equations with unknown free coefficients and control parameters. The validity and effectiveness of the method are demonstrated by solving some numerical examples. The results demonstrate that the proposed method is a powerful algorithm with good accuracy for solving such kind of problems.     

Evaluation of essential oils for maintaining postharvest quality of Thompson seedless table grape

The effects of postharvest spraying of essential oils from sweet basil (Ocimum basilicum), fennel (Foeniculum vulgare), summer savory (Satureja hortensis) and thyme (Thymus vulgaris) on fungal decay and quality parameters of the 'Thompson seedless' table grape stored at 0?±?1°C for 60 days were evaluated. Results showed that the essential oils, especially of thyme and fennel, have a good inhibitory effect on the development of fungal decay in Thompson table grapes. In addition, essential oils reduced weight loss, berry and rachis browning and had no considerable adverse effect on the flavour of the fruits. GC-MS analysis showed that the main compounds identified in sweet basil, fennel, summer savory and thyme oils are linalool (65.25%), trans-anethole (64.72%), carvacrol (54.14%) and β-ocimene (12.62%), respectively. Therefore, these essential oils have good potential for use as an alternative to synthetic fungicides for the preservation and storage of table grapes.     

A facile and one-pot electrochemical method for the synthesis of a new anthraquinonethioether

The reaction of electrochemically generated anthradiquinone as a Michael acceptor with 2-mercaptobenzothiazole and 2- mercaptobenzoxazole,as nucleophiles in ethanol/water mixtures has been studied by means of cyclic voltammetry.Our voltammetric data indicate that produced anthradiquinone participates in Michael addition reaction with nucleophiles and via an ECEC mechanism converts to the new anthraquinonethioether derivatives.Based on an EC mechanism,the observed homogeneous rate constant of the Michael reaction of anthradiquinone with nucleophiles were estimated by comparing the experimental cyclic voltammograms with the digital simulated results.     

High precision refractometry based on Fresnel diffraction from phase plates

When a transparent plane-parallel plate is illuminated at a boundary region by a monochromatic parallel beam of light, Fresnel diffraction occurs because of the abrupt change in phase imposed by the finite change in refractive index at the plate boundary. The visibility of the diffraction fringes varies periodically with changes in incident angle. The visibility period depends on the plate thickness and the refractive indices of the plate and the surrounding medium. Plotting the phase change versus incident angle or counting the visibility repetition in an incident-angle interval provides, for a given plate thickness, the refractive index of the plate very accurately. It is shown here that the refractive index of a plate can be determined without knowing the plate thickness. Therefore, the technique can be utilized for measuring plate thickness with high precision. In addition, by installing a plate with known refractive index in a rectangular cell filled with a liquid and following the described procedures, the refractive index of the liquid is obtained. The technique is applied to measure the refractive indices of a glass slide, distilled water, and ethanol. The potential and merits of the technique are also discussed.     

Complexation study of dibenzo-18-crown-6 with UO2 2+ cation in binary mixed non-aqueous solutions

The complexation reaction of macrocyclic ligand, dibenzo-18-crown-6 (DB18C6) with UO₂ ²⁺ cation was studied in ethylacetate-1,2-dichloroethane (EtOAc/DCE), acetonitrile-1,2-dichloroethane (AN/DCE), methanol-1,2-dichloroethane (MeOH/DCE) and ethanol-1,2-dichloroethane (EtOH/DCE) binary solutions at different temperatures using the conductometric method. The conductance data show that the stoichiometry of the complex formed between DB18C6 and UO₂ ²⁺ cation is affected by the nature of the solvent systems. A non-linear behaviour was observed for changes of log K _f of (DB18C6.UO₂)⁺² complex versus the composition of the binary mixed solvents. The values of thermodynamic quantities (?S°_c, ?H°_c) for formation of (DB18C6.UO₂)⁺² complex were obtained from temperature dependence of the stability constant using the van’t Hoff plots. The results show that in most cases, the complex is enthalpy stabilized and in all cases entropy stabilized and both parameters are affected by the nature and composition of the mixed solvents. In addition, the complex formation between dicyclohexyl-18-crown-6 (DCH18C6) and UO₂ ²⁺ cation was studied in pure AN and the results were compared with those of the (DB18C6.UO₂)⁺² complex.     

Oxidative Coupling of Dimethylformamide with β-Dicarbonyl Compounds Using γ-Fe2O3@CuO Nanoparticles

Russian Journal of Organic Chemistry - Maghemite–copper oxide nanocomposite catalyzed oxidative coupling of formamides with β-dicarbonyl compounds in the presence of tert-butyl...     

POSS nanocrosslinked poly (ethylene glycol) hydrogel as hybrid material support for silver nanocatalyst

Silver nanoparticles supported on polyhedral oligomeric silsesquioxane (OA‐POSS) nanocrosslinked poly (ethylene glycol)‐based hydrogels (PEG₆₀₀‐POSS/Ag NPs) as novel nanohybrid catalysts were synthesized for the first time. The as‐prepared nanohybrid hydrogels were fully characterized by FT‐IR, SEM, EDX, XRD, TEM and TGA. PEG₆₀₀‐POSS/Ag NPs exhibited excellent catalytic performance for the reduction of 4‐nitrophenol (4‐NP) to 4‐aminophenol (4‐AP) in water at room temperature in the presence of borohydride.