A catalytic oxidative esterification of aldehydes using V2O5-H2O2

[reaction: see text] Aldehydes, in the presence of methanol, undergo oxidative transformation to the corresponding esters upon treatment with catalytic amounts of vanadium pentoxide in combination with oxidant hydrogen peroxide. Mild reaction conditions, shorter reaction times, high efficiencies, cost-effectiveness, and facile isolation of the desired products make the present methodology a practical alternative.     

Every T-space is equivalent to a T-space of continuous functions

A T-space U of degree k is a (k + 1)-dimensional vector space over (the real line) of real-valued functions defined on a linearly ordered set, satisfying the condition: for every nonzero u ε U, Z(u), the number of distinct zeros of u and ^-(u), the number of alternations in sign of u(t) with increasing t, each do not exceed k. It is demonstrated that given a T-space U of degree k > 0 on an arbitrary linearly ordered set T, there is a subset T′ of the real line and a nonsingular linear map L:U→ C(T′), the set of continuous functions on T′, such that the following hold: L(U) is a T-space of degree k; for u ε U, Z(u) = Z(L(u)), S^−(u) = S^−(L(u); and for some order-preserving bijection Θ:T → T′, u(t) = O if and only if L(u)(Θ(t) = 0. It is also shown that a T-space on a subset T can be extended to a T-space on the closure of T in ]inf T, sup T], provided that there are no “interval gaps” in T. Examples show that, in general, a T-space cannot be extended across an “interval gap” in its domain, and cannot be extended to both the infimum and supremum of its domain. Conditions for a T-space to be Markov, and to admit an adjoined function are derived.     

Mediator-free simultaneous determination of acetaminophen and caffeine using a glassy carbon electrode modified with a nanotubular clay

Microchimica Acta - The authors describe a voltammetric method for the simultaneous determination of acetaminophen (ACOP) and caffeine (CAF) using a glassy carbon electrode modified with a...     

Reply to the Letter-to-the-Editor of Dr. Noble Jacob regarding article “Radon isotope assessment of Submarine Groundwater Discharge (SGD) in Coleroon River Estuary,Tamil Nadu,India”, DOI: https://doi.org/10.1007/s10967-018-5877-2

Journal of Radioanalytical and Nuclear Chemistry -     

Synthesis of new binol based [1+1] macrocyclic chiral manganese(III) Schiff bases as catalysts for asymmetric epoxidation

A series of new chiral binol based [1+1] macrocyclic Schiff bases have been synthesized in high yields in short reaction times via cyclo-condensation of dialdehydes with long tethers and chiral diamines. Macrocyclic Mn(salen) complexes containing N₂O₂ salen units incorporated with spacers of increased tether lengths were synthesized and characterized. The newly synthesized catalyst system was successfully employed for the enantioselective epoxidation of unfunctionalized olefins with high yields and good enantioselectivity.     

Development and validation of a sensitive and high‐throughput LC‐MS/MS method for the simultaneous determination of esomeprazole and naproxen in human plasma

A sensitive and high‐throughput LC‐MS/MS method has been developed and validated for the combined determination of esomeprazole and naproxen in human plasma with ibuprofen as internal standard. Solid‐phase extraction was used to extract both analytes and internal standard from human plasma. Chromatographic separation was achieved in 4.0 min on XBridge C₁₈ column using acetonitrile–25 mM ammonium formate (70:30, v/v) as mobile phase. Mass detection was achieved by ESI/MS/MS in negative ion mode, monitoring at m/z 344.19 → 194.12, 229.12 → 169.05 and 205.13 → 161.07 for esomeprazole, naproxen and IS, respectively. The calibration curves were linear from 3.00 to 700.02 ng/mL for esomeprazole and 0.50 to 150.08 ng/mL for naproxen. The intra‐ and inter‐batch precision and accuracy across four quality control levels met established criteria of US Food and Drug Administration guidelines. The assay is suitable for measuring accurate esomeprazole and naproxen plasma concentrations in human bioequivalence study following combined administration. Copyright © 2013 John Wiley & Sons, Ltd.     

Pumice-based sulfonic acid: a sustainable and recyclable acidic catalyst for one-pot synthesis of pyrazole anchored 1,4-dihydropyridine derivatives at room temperature

Research on Chemical Intermediates - In the present investigation, we have developed an efficient and eco-friendly protocol for the synthesis of pyrazole anchored 1,4-dihydropyridine analogs using...     

A radical mediated first total synthesis from ‘diacetone glucose’ and determination of the absolute stereochemistry of xylobovide

The first total synthesis by an intramolecular radical cyclisation protocol on a carbohydrate derived 5-hexynyl system, and determination of the absolute stereochemistry of xylobovide are reported.     

Magnetoelectric effect in cobalt ferrite-barium titanate composites and their electrical properties

CoFe₂O₄-BaTiO₃ composites were prepared using conventional ceramic double sintering process with various compositions. Presence of two phases in the composites was confirmed using X-ray diffraction. The dc resistivity and thermoemf as a function of temperature in the temperature range 300 K to 600 K were measured. Variation of dielectric constant (ɛ′) with frequency in the range 100 Hz to 1 MHz and also with temperature at a fixed frequency of 1 kHz was studied. The ac conductivity was derived from dielectric constant (ɛ′) and loss tangent (tan δ). The nature of conduction is discussed on the basis of small polaron hopping model. The static value of magnetoelectric conversion factor has been studied as a function of magnetic field.