Temperature‐ and pressure‐dependent study of 35Cl NQR frequency and spin lattice relaxation time in 2,3‐dichloroanisole

The temperature and pressure dependence of ³⁵Cl NQR frequency and spin lattice relaxation time (T₁) were investigated in 2,3‐dichloroanisole. Two NQR signals were observed throughout the temperature and pressure range studied. T₁ were measured in the temperature range from 77 to 300 K and from atmospheric pressure to 5 kbar. Relaxation was found to be due to the torsional motion of the molecule and also reorientation of motion of the CH₃ group. T₁ versus temperature data were analyzed on the basis of Woessner and Gutowsky model, and the activation energy for the reorientation of the CH₃ group was estimated. The temperature dependence of the average torsional lifetimes of the molecules and the transition probabilities were also obtained. NQR frequency shows a nonlinear behavior with pressure, indicating both dynamic and static effects of pressure. The pressure coefficients were observed to be positive for both the lines. A thermodynamic analysis of the data was carried out to determine the constant volume temperature coefficients of the NQR frequency. The variation of spin lattice time with pressure was very small, showing that the relaxation is mainly due to the torsional motions of the molecules. Copyright © 2010 John Wiley & Sons, Ltd.     

Liquid chromatography–tandem mass spectrometric assay for the determination of tetrabenazine and its active metabolites in human plasma: a pharmacokinetic study

A simple, rapid and sensitive liquid chromatography–tandem mass spectrometric (LC‐MS/MS) assay method has been developed and fully validated for the simultaneous quantification of tetrabenazine and its active metabolites α‐dihydrotetrabenazine and β‐dihydrotetrabenazine in human plasma. Tetrabenazine d7 was used as internal standard (IS). The analytes were extracted from 200 μL aliquots of human plasma via solid‐phase extraction using C₁₈ solid‐phase extraction cartridges. The reconstituted samples were chromatographed on a Zorbax SB C₁₈ column using a 60:40 (v/v) mixture of acetonitrile and 5 mm ammonium acetate as the mobile phase at a flow rate of 0.8 mL/min. The API‐4000 LC‐MS/MS in multiple reaction‐monitoring mode was used for detection. The calibration curves obtained were linear (r² ≥ 0.99) over the concentration range of 0.01–5.03 ng/mL for tetrabenazine and 0.50–100 ng/mL for α‐dihydrotetrabenazine and β‐dihydrotetrabenazine. Method validation was performed as per Food and Drug Administration guidelines and the results met the acceptance criteria. The method is precise and sensitive enough for its intended purpose. A run time of 2.5 min for each sample made it possible to analyze more than 300 plasma samples per day. The proposed method was found to be applicable to clinical studies. Copyright © 2013 John Wiley & Sons, Ltd.     

Interlaboratory calibration of track-etch detectors for the measurement of radon and radon daughter levels

This paper reports the results of the second interlaboratory calibration experiments, which were carried out in two parts. In the first, five types of commercially available and economically cheap membranes were tested as the barrier against thoron for “radon-only” measurements. It was found that all the membranes tested are good barriers against thoron and can be used in the “radon-only” device. In the second, actual calibration experiments were performed with LR-115 type-II and CR-39 track-etch detectors for different radon measuring configurations in a radon exposure chamber.     

Sulfoximines: a reusable directing group for chemo- and regioselective ortho C-H oxidation of arenes

Sulfoximines direct: a new protocol for the chemo- and regioselective ortho C-H acetoxylation of arenes in N-benzoylated sulfoximines is reported. The sulfoximine directing group is easily detached from the C-H oxidation product through acid-promoted hydrolysis, isolated, and reused. The meta-substituted phenols are synthesized following this strategy and the stereointegrity of the sulfoximine is preserved in this transformation. C(sp(3))-H acetoxylation of the methyl group is also demonstrated.     

Stereoselective Glycosylation of Glucosamine: The Role of the N‐Protecting Group

Oligosaccharides and glycoconjugates play an important role in biological processes. The use of these complex polymers as biocompatible materials for medicinal applications as well as therapeutic agents for the treatment of several diseases has attracted considerable interest. However, these investigations require large and pure amounts of glycostructures. Glucosamine is one of the major building blocks of these highly important glycoconjugates. Recently, considerable synthetic efforts have been devoted to improving stereoselective glycosylation. In this Focus review, the role of the amine protecting group in the outcome of the glucosamine glycosylation reaction is highlighted.     

An Alumina Based 99Mo–99mTc Generator to Produce 99mTc in Organic Medium Suitable for Industrial Radiotracer Applications

An industrial chromatographic ⁹⁹Mo–^99mTc generator has been developed with the aid of chromatographic alumina to obtain ^99mTc in a non-aqueous medium. This generator system takes advantage of tributyl phosphate to extract ^99mTc selectively with appreciable yield and in high radiochemical and radionuclidic purity. This facile, versatile and efficient approach provides ^99mTc at industrial sites in a medium soluble in hydrocarbon solvents, for radiotracer applications.     

Electrochemically Deposited Porous Graphene−Polypyrrole−Polyphenol Oxidase for Dopamine Biosensor

We report a method for the fabrication of glassy carbon electrode modified porous graphene-polypyrrole-polyphenol oxidase (GCE−PG−PPy−PPO) modified electrode for the determination dopamine. The optimization of pH, concentration and detection limit of dopamine was employed by amperomatric technique. The detection limit of dopamine was found to be in a linear range of 2×10⁻⁸ to 4.6×10⁻⁵ M and lower limit detection is 4×10⁻⁹ M. Michealis – Menten constant (Km) and the activation energy were calculated as 31.32 μM and 37.4−Kj mol⁻¹, respectively. The developed biosensor was used to quantify the dopamine in human urine sample.     

Ruthenium(III) chloride-catalyzed efficient protocol for ethyl diazoacetate insertion into the N–H bond of secondary amines

Ruthenium(III) chloride (1 mol%) alone can catalyze the insertion of ethyl diazoacetate into N–H bonds of various structurally and electronically diverse secondary cyclic amines under solvent-free conditions to afford the corresponding glycine esters in good yields under ambient conditions. Reactions with various aliphatic primary and aromatic amines examined, however, were unsuccessful. Correspondence: Dr. Srinivas R. Adapa, Indian Institute of Chemical Technology, Hyderabad 500 007, India.     

Electrochemical impedance spectroscopic studies on aging-dependent electrochemical degradation of p-toluene sulfonic acid-doped polypyrrole thin film

The conducting polymer polypyrrole thin film was galvanostatically polymerized on stainless steel substrate for the supercapacitor electrode. The electrochemical stability of the electrode was monitored each 30 days of aging up to 90 days. The FTIR analysis showed an increase in intensity of the absorption peaks, especially high growth of the carbonyl peaks after 90 days of aging. The electrochemical capacitance degradation of the electrode was studied using cyclic voltammetric and galvanostatic charge/discharge analysis in 1 M Na₂SO₄ electrolyte, which showed ~?53% of fading in the initial specific capacitance value after 90 days. Further, the electrochemical degradation of polypyrrole electrodes was analyzed in detail using electrochemical impedance spectroscopy. The analysis showed a large increase in the internal resistance and low-power deliverability of the electrode with respect to aging as the main reasons for the degradation of specific capacitance of the polypyrrole electrode.