Extraction and spectrophotometric determination of vanadium as a mixed ligand complex of oxine and azide

Summary Vanadium, oxine and azide react at pH 3.5–4.5 to give a dark green solid which extracts into benzene giving dark green solution. The extract has absorption maxima at 415 nm and 620 nm with molar absorptivities 8650 and 6040 respectively. Spectrophotometric investigations reveal that the extracting species has V, HOx and N₃ ^– in the ratio 122. Beer's law is obeyed upto 8.10g and 10.50g of vanadium per ml at 415 nm and 620 nm respectively. The formation constant and the free energy of formation are 8.5 ± 0.2×10⁶ and –9.61±0.30 Cal respectively at 30°. The interference of various foreign ions are studied and methods are proposed for the elimination of the interference of some of those substances. Infrared and magnetic data of the solid complex are given.

---

Zusammenfassung Vanadin, Oxin und Azid reagieren bei pH 3,5–4,5 zu einem dunkelgrünen Feststoff, der sich mit Benzol als dunkelgrüne Lösung extrahieren läßt. Deren Absorptionsmaxima liegen bei 415 und 620 nm mit den molaren Extinktionen von 8650 bzw. 6040. Spektrophotometrisch ergibt sich das Verhältnis V:HOx: N₃ ^–=122. Bis 8,10 bzw. 10,5g V hat das Beersche Gesetz Gültigkeit. Die Komplexkonstante beträgt 8,5 ± 0,2×10⁶, die Bildungswärme –9,61±0,3 Kcal bei 30° C. Die Störung durch verschiedene Fremdionen wurde geprüft und in einigen Fällen beseitigt. IR- und magnetische Daten für die feste Komplexverbindung werden angegeben.

     

Glycosphingolipid with a branched sphingosine base from soft corals from the Andaman Islands

New cerebroside with the structure of 1-(-d-glucopyranosyloxy)-2-N-(2-hydroxyacyl)-erythro-2-amino-9-methyloctadeca-4E,8E-dien-3-ol (1) was isolated from the soft coral Cladiellasp. collected on the seaboard of the Andaman Islands (Indian Ocean). The acyl groups in compound 1 were identified as residues of d-2-hydroxy-C_20:0, -C_21:0, and -C_22:0 acids.     

Non Solvent Reaction: Ammonium Acetate Catalyzed Highly Convenient Preparation of Trans-Cinnamic Acids

trans-Cinnamic acids were obtained in near quantitative yield when various aromatic aldehydes were heated with equimolar quantity of malonic acid in presence of ammonium acetate under solvent free conditions. Considerable enhancement in the rate of the reaction was observed when the decarboxylative condensation was carried out under microwave irradiation.

     

Nonperturbative chemical modification of graphene for protein micropatterning

Graphene's extraordinary physical properties and its planar geometry make it an ideal candidate for a wide array of applications, many of which require controlled chemical modification and the spatial organization of molecules on its surface. In particular, the ability to functionalize and micropattern graphene with proteins is relevant to bioscience applications such as biomolecular sensors, single-cell sensors, and tissue engineering. We report a general strategy for the noncovalent chemical modification of epitaxial graphene for protein immobilization and micropatterning. We show that bifunctional molecule pyrenebutanoic acid-succinimidyl ester (PYR-NHS), composed of the hydrophobic pyrene and the reactive succinimide ester group, binds to graphene noncovalently but irreversibly. We investigate whether the chemical treatment perturbs the electronic band structure of graphene using X-ray photoemission (XPS) and Raman spectroscopy. Our results show that the sp(2) hybridization remains intact and that the π band maintains its characteristic Lorentzian shape in the Raman spectra. The modified graphene surfaces, which bind specifically to amines in proteins, are micropatterned with arrays of fluorescently labeled proteins that are relevant to glucose sensors (glucose oxidase) and cell sensor and tissue engineering applications (laminin).