Application of high-melting pyridinium salts as ionic liquid catalysts and media for fischer esterification

Pyridinium methanesulfonate (m.p. 185°C) and pyridinium p-toluenesulfonate (m.p. 121°C) were used as catalysts and media for the esterification of carboxylic acids with primary alcohols to give the corresponding esters selectively in high yields. The high melting points of these pyridinium salts did not prevent their application as ionic liquid medium for these reactions which were performed at 90°C.     

Cyclodehydration of 1,4-butanediol catalyzed by metal(IV) phosphates

Metal(IV) phosphates of tin, zirconium and titanium in different morphological forms, viz. amorphous, calcined and crystalline, have been used as catalysts for selective cyclodehydration of 1,4-butanediol to tetrahydrofuran. A comparative study of the three catalysts for the above reaction has been carried out to understand the effect of their composition and morphology on the catalytic activity.     

高效固体酸SBA-15-Zr(OTf)3催化胺或醇开环环氧化合物

通过简单的一锅两步法制备了三氟金属(铝,钛,锆)接枝介孔SBA-15 (AlTf/S,TiTf/S,ZrTf/S)固体酸材料,并通过XRD,N2吸附,TGA,FTIR,原位吡啶FTIR和元素分析对这些材料进行了详细的表征.其中,ZrTf/S能够高效催化环氧化物温和条件下被胺或醇开环生成对应β-氨基醇或β-烷氧基醇,并且催化剂能循环利用.ZrTf/S相较于AlTf/S和TiTf/S酸性最强,因而催化活性也最高.     

Fluorogenic ratiometric dipodal optode containing imine-amide linkages: Exploiting subtle thorium (IV) ion sensing

The (13E,19E)-N1′,N3′-bis[4-(diethylamino)-2-hydroxybenzylidene]malonohydrazide (L) has been developed for the detection of Th⁴⁺ ions using dual channel signalling system. The UV–vis absorbance and fluorescence spectroscopic data revealed the formation of L–Th⁴⁺ complex in 1:1 equilibrium. The density functional theory (DFT) also confirms the optimum binding cavity for the recognition of metal ion. The binding constant computed from different mathematical models for an assembly of L–Th⁴⁺. The detection limit of L for Th⁴⁺ recognition is to a concentration down to 0.1 μM (0.023 μg g⁻¹). The present sensing system is also successfully applied for the detection of Th⁴⁺ ion present in soil near nuclear atomic plants.     

Production, Purification, and Biochemical Characterization of a Fibrinolytic Enzyme from Thermophilic Streptomyces sp. MCMB-379

Production of the fibrinolytic enzyme was carried out using 2.5-L glass fermentor, culture of thermophilic Streptomyces sp., and glucose yeast extract peptone medium of pH 8.0. Five successive batches were carried out under controlled fermentation conditions viz., agitation 140 rpm, aeration 0.5 vvm, 55 °C, and 18 h. The total protein extracellularly produced in the cell-free broth was ~300-500 mg/L. The enzyme belongs to serine endopeptidase type. Studies on the fibrin degradation indicate that the enzyme degrades the fibrin into small molecular weight products as seen from HPLC profile. Phase-contrast microscopic structure of fibrin showed that enzyme cleaves the fibrin filaments. The ex vivo activity of the actinokinase was compared with 500 IU of urokinase and 350 IU of streptokinase. The ex vivo clot lysis was found to be faster as compared to the commercial available enzymes.     

Coordination polymers of CdII and PbII derived from bipyridine–glycoluril: influence of metal‐ion size and counter‐ions

Two new one‐dimensional (1D) coordination polymers (CPs), namely catena‐poly[[[aquacadmium(II)]‐bis(μ‐4b,5,7,7a‐tetrahydro‐4b,7a‐epiminomethanoimino‐6H‐imidazo[4,5‐f][1,10]phenanthroline‐6,13‐dione)] bis(perchlorate) dihydrate], {[Cd(C₁₄H₁₀N₆O₂)₂(H₂O)](ClO₄)₂·2H₂O}_n or {[Cd(BPG)₂(H₂O)](ClO₄)₂·2H₂O}_n, 1 , and catena‐poly[[lead(II)‐bis(μ‐4b,5,7,7a‐tetrahydro‐4b,7a‐epiminomethanoimino‐6H‐imidazo[4,5‐f][1,10]phenanthroline‐6,13‐dione)] bis(perchlorate) dihydrate], {[Pb(C₁₄H₁₀N₆O₂)₂](ClO₄)₂·2H₂O}_n or {[Pb(BPG)₂](ClO₄)₂·2H₂O}_n, 2 , have been synthesized using bipyridine–glycoluril (BPG; systematic name: 4b,5,7,7a‐tetrahydro‐4b,7a‐epiminomethanoimino‐6H‐imidazo[4,5‐f][1,10]phenanthroline‐6,13‐dione), a urea‐fused tecton, in a mixed‐solvent system. The Cd^II ion in 1 is heptacoordinated and the Pb^II ion in 2 is hexacoordinated, with the Cd^II ion adopting a pentagonal bipyramidal geometry and the Pb^II ion adopting a distorted octahedral geometry. Both CPs form infinite linear chain structures which are hydrogen bonded to each other leading to the formation of three‐dimensional supramolecular network structures. Topological analysis of CPs 1 and 2 reveals that the structures exhibit 1D chain‐like arrangements in an AB–AB sequence and shows platonic uniform 2‐connected uninodal topologies. Furthermore, a comparative analysis of a series of structures based on the BPG ligand indicates that the size of the metal ion and the types of counter‐ions used have a great influence on the resulting frameworks and properties.     

Hydrothermal Assisted Synthesis of Micro-Bricks Shaped WO3 for Electrochemical Oxidation of Paracetamol: A Microstructured Paracetamol Sensor

Russian Journal of Electrochemistry - A micro-bricks shaped tungsten oxide (WO3) was prepared by hydrothermal method. The prepared material was characterized by field emission scanning electron...     

Intermolecular interactions in dioxane-water solutions of substituted coumarins according to ultrasonic data

Density, ultrasonic velocity of pure dioxane (Dx) and ligands, 4,6-dimethyl-7-hydroxycoumarin (L₁), 6-ethyl-7-hydroxy-4-methylcoumarin (L₂), and 3-chloro-7-hydroxy-4-methylcoumarin (L₃) in different percent of Dx-water mixture have been investigated at 303.15 K. Acoustical parameters such as adiabatic compressibility (β), intermolecular free length (L _f ), acoustical impedance (Z), relative association (R _A ), apparent molar compressibility (Φ_β), and apparent molar volume (Φ _V ) have also been evaluated from the experimental data of density and ultrasonic velocity. An excellent correlation between a given parameters is observed at all percent of dioxane-water and the result suggests nature of intermolecular interactions between the components.     

Sequential determination of fat- and water-soluble vitamins in Rhodiola imbricata root from trans-Himalaya with rapid resolution liquid chromatography/tandem mass spectrometry

A rapid method was developed to determine both types of vitamins in Rhodiola imbricata root for the accurate quantification of free vitamin forms. Rapid resolution liquid chromatography/tandem mass spectrometry (RRLC–MS/MS) with electrospray ionization (ESI) source operating in multiple reactions monitoring (MRM) mode was optimized for the sequential analysis of nine water-soluble vitamins (B₁, B₂, two B₃ vitamins, B₅, B₆, B₇, B₉, and B₁₂) and six fat-soluble vitamins (A, E, D₂, D₃, K₁, and K₂). Both types of vitamins were separated by ion-suppression reversed-phase liquid chromatography with gradient elution within 30 min and detected in positive ion mode. Deviations in the intra- and inter-day precision were always below 0.6% and 0.3% for recoveries and retention time. Intra- and inter-day relative standard deviation (RSD) values of retention time for water- and fat-soluble vitamin were ranged between 0.02–0.20% and 0.01–0.15%, respectively. The mean recoveries were ranged between 88.95 and 107.07%. Sensitivity and specificity of this method allowed the limits of detection (LOD) and limits of quantitation (LOQ) of the analytes at ppb levels. The linear range was achieved for fat- and water-soluble vitamins at 100–1000 ppb and 10–100 ppb. Vitamin B-complex and vitamin E were detected as the principle vitamins in the root of this adaptogen which would be of great interest to develop novel foods from the Indian trans-Himalaya.     

Cobalt(II), nickel(II) and copper(II) with 2-substituted benzimidazole complexes

Summary Complexes of stoichiometries M(Acbim)₂X₂·nH₂O and M(Bzbim)₂X₂·nH₂O (M = Co, Ni or Cu; Acbim = 2-acetylbenzimidazole, Bzbim = 2-benzoylbenzimidazole; X = Cl, Br, NO₃ or ClO₄; n = 0, 1 or 2) have been prepared and characterised by spectroscopic and physicochemical methods. The ligands coordinate through carbonyl oxygen and tertiary nitrogen.