Synthesis of the A,B,C-ring system of hexacyclinic acid

[structure: see text] The synthesis of the A,B,C-ring system (2) of hexacyclinic acid (1) is achieved starting from a selective Diels-Alder reaction followed by vinyl cuprate addition. The diastereoselective reduction of the ketone carbonyl at C16 could be achieved with LiAlH(4). An intramolecular Michael addition established the ring system stereoselectively, providing access to the selective generation of 9 out of the 14 stereocenters of hexacyclinic acid.     

Separation and identification of metal dithizonates by thin-layer chromatography and its application in toxicological analysis

Summary A thin-layer Chromatographic investigation was carried out on Silica Gel-G plates for metal dithizonates and the technique was applied for detecting metals present in autopsy tissues in cases of suspected suicide and homicide. R_f values of the common metal complexes in four Chromatographic solvents and the colour of their respective spots on the TLC plate are reported.

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Zusammenfassung Die Dünnschichtchromatographie von Metalldithizonaten auf Silicagel G-Platten wurde mit dem Ziel untersucht, Metalle in Leichenteilen nach Selbstmord oder Mord nachweisen zu können. Die R_f-Werte der Dithizonate üblicher Metalle in vier zur Chromatographie verwendeten Lösungsmitteln und die Farbe der Chromatogrammflecken wurden angegeben.

     

Extraction-Spectrophotometric Determination of Fluoride Using N-Phenylbenzohydroxamic Acid

Abstract

Fluoride gives a very stable complex with scandium and, hence, by determining the unreacted scandium, the fluoride content can be calculated. Excess scandium is reacted with an ethanolic solution of N-benzoylphenylhydroxylamine (BPHA) at pH 6.0, and the scandium-BPHA complex is extracted into isoamyl alcohol. Scandium is determined spectrophotometrically after adding xylenol orange. Beer's law for fluoride is obeyed in the range of 0.05 –1.5 ppm; the molar absorptivity is 1.94×10⁴ 1 mol^?1 at 565 nm. The procedure is applicable for the determination of fluoride in various types of samples.     

Radiation effect on thermoluminescence and electron paramagnetic resonance (EPR) of pink beryl

Morganite, a pink beryl with the chemical formula Be₃Al₂Si₆O₁₈, was investigated in terms of its thermally stimulated luminescence (TL) and electron paramagnetic resonance (EPR) properties due to point defects. Atomic hydrogen H°-centers were induced by γ-radiation and shown to be responsible for a 165°C TL peak. The Fe³⁺-center concentration was found to increase with γ-dose, observed by both TL and EPR measurements, decreasing with thermal treatments beyond 250°C. A mechanism for emission around 315°C is proposed.     

A review on use of TRNSYS as simulation tool in performance prediction of desiccant cooling cycle

Journal of Thermal Analysis and Calorimetry - Solid desiccant-assisted cooling and dehumidification systems are becoming very popular nowadays for maintaining the required thermal comfort in...