Highly selective trifluoroacetic ester/ketone metathesis: an efficient approach to trifluoromethyl ketones and esters

A highly selective and atom efficient ‘trifluoroacetic ester/ketone metathesis’ has been sincerely witnessed. Enolizable alkyl (at least two non-hydrogen atoms) aryl ketones were found to react readily with ethyl trifluoroacetate under the promotion of NaH to afford trifluoroacetic ester/ketone exchange products, trifluoromethyl ketones (TFMKs), and aromatic acid esters, which were quite different from the general Claisen condensation products, 1,3-diketones. The outcome of the reaction between ketone and ethyl trifluoroacetate is strongly related to the structures of substrates, the steric congestion caused by alkyl group is in favor of the C–C bond cleavage. DFT investigation further disclosed that the metathesis reaction was a kinetically favored pathway. Using only a slight excess of cheap trifluoromethylation reagent, simple operation and mild conditions make it a practical method for preparation of TFMKs on large scale, as well as a new choice of converting aryl alkyl ketones to aromatic acid esters.     

Revisit of a series of ICT fluorophores: skeletal characterization,structural modification,and spectroscopic behavior

We have revisited the synthesis of a series of ICT fluorophores, which were reported to have a core structure of 8-oxo-8H-acenaphtho[1,2-b]pyrrol-9-carbonitrile. However, based on the 2D NMR and X-ray diffraction analysis, their core structure was corrected as 1-oxo-1H-phenalene-2,3-dicarbonitrile (1). Compound 1 shows a highly electron-deficient nature and can easily undergo oxidative S_NAr^H reaction on the naphthyl ring to produce a series of novel ICT fluorophores. The regioselectivity of this substitution reaction was studied by introduction of representative nucleophiles. Moreover, due to the strong rigidity and efficient ICT nature, the obtained fluorescent dyes display very good spectroscopic properties even in an aqueous environment.     

Study of Cl−(H2O)n (n = 1–4) using basin‐hopping method coupled with density functional theory

Cl^?(H₂O)_n (n = 1–4) clusters were investigated using a basin‐hopping (BH) algorithm coupled with density functional theory (DFT). Structures, energetics, thermodynamics, vertical detachment energies, and vibrational frequencies were obtained from high‐level ab initio calculations. Through comparisons with previous theoretical and experimental data, it was demonstrated that the combination of the BH method and DFT could accurately predict the global and local minima of Cl^?(H₂O)_n (n = 1–4). Additionally, to optimize larger Cl^?(H₂O)_n (n > 4) clusters, several popular density functionals as well as DF‐LMP2 (Schütz et al., J. Chem. Phys. 2004, 121, 737) (second‐order Møller‐Plesset perturbation theory using local and density fitting approximations) were tested with appropriate basis sets through comparisons with MP2 optimized results. DF‐LMP2 will be used in future studies because its overall performance in describing the relative binding energies and the geometrical parameters of Cl^?(H₂O)_n (n = 1–4) was outstanding in this study. © 2013 Wiley Periodicals, Inc.     

Environmental gamma background measurements in China Jinping Underground Laboratory

To determine the environmental gamma background levels which affects rare events experiments, we measured in situ gamma spectrum at four locations in the China Jinping Underground Laboratory. The integral background count rates (40–2,700 keV) varied from 3.76 to 74.1 cps. The average count rate of the measurements inside the CJPL was 73.4 cps. The spectrometer was calibrated with a ¹⁵²Eu point source and Monte Carlo simulation to obtain the activity conversion factors for the rock and the air, respectively. The rocks that surrounded the CJPL was characterized by very low activity concentrations of ²³⁸U (3.69–4.21 Bq kg^?1), ²³²Th (0.52–0.64 Bq kg^?1) and ⁴⁰K (4.28 Bq kg^?1).     

Effects of Sodium Salts Organic Acids Modification on the Microstructure and Dispersion Behavior of Palygorskite Nano-Powder via High-Pressure Homogenization Process

High-pressure homogenization could disaggregate the crystal bundles of palygorskite and favor the adsorption of electrolyte ions onto its surface through the produced cavitation, shear, and turbulence forces, and has evident influences on the micromorphologies and properties of clay. In this work, a series of palygorskite samples modified with sodium citrate, sodium benzoate, sodium lactate, sodium acetate, and sodium propionate were obtained under the condition of high-pressure homogenization. The effects of type and concentration of sodium salts organic acids on the microstructure, morphology, surface charge, and physicochemical property of palygorskite were studied through x-ray diffraction (XRD), N₂ adsorption–desorption isotherm, field emission scanning electron microscopy, zeta potential, rotational viscosity, and rheological measurements. XRD results confirmed that the crystal structure of homogenized palygorskite was not changed after introduction of sodium salts organic acids, but the aggregates were effectively disaggregated. Modification of palygorskite with sodium citrate made the surface more negatively charged, and the samples exhibited higher specific surface area and rheological properties. This work provided a method to improve the rheological properties of palygorskite suspension through dispersion of clay in sodium citrate solution followed by homogenization at 30 MPa.      

A simple and economic method for accurate determination of the energy peak efficiency of 208 keV γ-ray of 237U based on 241Pu/237U secular equilibrium

A new method is developed for the determination of energy peak efficiency of 208 keV γ-ray of ²³⁷U based on ²⁴¹Pu/²³⁷U secular equilibrium. Plutonium solution was purified to remove Am with Dowex 1 × 2 anion exchange chromatography and the concentration of ²⁴¹Pu in the purified solution was determined using ²⁴²Pu isotope-dilution mass spectrometry on an inductively-coupled plasma mass spectrometry. The solution can be used as calibration source for the determination of energy peak efficiency of 208 keV γ-ray of ²³⁷U after 48 days. The method was validated for a planar HPGe detector at the 12 mm above the detector surface. The results showed that this is a simple and economic method for determining the energy peak efficiency of gamma detectors for 208 keV γ-ray of ²³⁷U.     

Removal of uranium from aqueous solution by using activated palm kernel shell carbon: adsorption equilibrium and kinetics

Activated palm kernel shell carbon (APKSC) was used to remove U(VI) from aqueous solutions in a batch system. The adsorption kinetics, isotherms, and effects of various parameters, such as temperature, contact time, solution pH, adsorbent dosage, and initial U(VI) concentration on the U(VI) adsorption process were studied. Equilibrium was reached after 120 min in the range of studied U(VI) concentrations and temperatures. U(VI) uptake was insignificantly affected by temperature, but was highly pH dependent, and the optimum pH for removal was 5.5. U(VI) removal efficiency increased with the increasing adsorbent dosage. U(VI) sorption capacity increased with increasing initial U(VI) concentration; any further increases in initial U(VI) concentration above a certain point caused insignificant changes in U(VI) sorption capacity. Isotherm data could be described by the Langmuir isotherm model with a maximum U(VI) adsorption capacity of 51.81 mg/g. Kinetic data were fitted to pseudo-first-order and pseudo-second-order equations, which suggested that the U(VI) adsorption onto APKSC was better reproduced by the pseudo-second-order model rather than pseudo-first-order model. Our results indicated that APKSC might be used as a cheap adsorbent in the treatment of uranium-containing wastewater.     

Development and validation of a hydrophilic interaction liquid chromatography with tandem mass spectrometry method for the simultaneous detection and quantification of etilefrine and oxilofrine in equine blood plasma and urine

A sensitive hydrophilic interaction liquid chromatography coupled with tandem mass spectrometry method was developed and validated for the simultaneous detection and quantification of etilefrine and oxilofrine in equine blood plasma and urine. The method is highly sensitive and specific with good precision and accuracy. In plasma the limit of detection and limit of quantification are 0.03 and 0.1 ng/mL, respectively, for both analytes. In urine the limit of detection and limit of quantification are 0.3 and 1 ng/mL, respectively, for both analytes. The suitability of the method for doping control analysis in equine species is demonstrated by analyzing postadministration samples collected after a single intravenous administration of 50 mg etilefrine to a standardbred mare. Etilefrine was detected up to 120 h in urine and up to 48 h in plasma. Etilefrine is highly conjugated in equine urine whereas it exists in the free form in equine plasma. Therefore, enzyme hydrolysis prior to sample preparation is recommended for the detection and quantification of etilefrine and oxilofrine in equine urine.     

Extraction of coal-tar pitch using NMP/ILs mixed solvents

Coal-tar pitch(CP)is a promising carbon raw material for producing needle coke,carbon fiber etc.During processing,the H/C ratio,ash content,and quinoline insoluble(QI)in the CP are the key factors that influence the material preparation.In this study,NMP was selected to extract CP first;then[BMIM]Cl/NMP mixed solvent was used;and finally a series of ionic liquids(ILs)mixtures with NMP were developed for the extraction of CP to obtain the refined pitch.The extracts were analyzed via elemental analysis,TGA,FT-IR,and 13C-NMR.Results indicate that different NMP/IL mass ratios or different kinds of ILs have impact on the extraction yield.The relationship of the hydrogen to carbon(H/C)ratio changed with different solvents and QI extracts were obtained.Results showed that the H/C ratios changed little between NMP extracts and could be adjusted by changing the NMP/ILs mass ratio or using different ILs.The extracts are suitable for preparation mesophase pitch because of no ash content,low QI,and appropriate H/C ratios.As a result,NMP can be used to refine pitch.In addition,[BMIM]Cl is good mixed with NMP for CP extraction,because it can obtain a relatively high yield under the same extraction conditions.