Mechanistic study of osmium(VIII) promoted oxidation of crotonic acid by aqueous alkaline solution of potassium bromate

Kinetics and mechanism of the Os(VIII) catalysed oxidation of crotonic acid (CA) by KBrO₃ in alkaline medium have been investigated. Zero order dependence in [KBrO₃] was observed, while first order with respect to CA in its lower concentration range tends to zero order at its higher concentration range. The order in [Os(VIII)] was found to be unity and a positive effect of [OH⁻] was observed. Variation of the ionic strength (μ) and dielectric constant of the medium and addition of Hg(OAc)₂ (used as Br⁻ scavenger) had an insignificant effect on the rate of reaction. Thermodynamic parameters have also been calculated and reported. A suitable mechanism consistent with the observed kinetic results has been suggested and the related rate law deduced.     

Electrochemical oxidation of sulphapyridine at a pyrolytic graphite electrode

The electrochemical oxidation of sulphapyridine at a pyrolytic graphite electrode was studied over a wide pH range. Sulphapyridine is oxidized in an irreversible reaction involving two electrons and two protons to give an electroactive product. On the basis of voltammetric, spectral and coulometric studies and product identification, a tentative mechanism is suggested.     

Solution-processed electrochemical synthesis of ZnFe2O4 photoanode for photoelectrochemical water splitting

Journal of Solid State Electrochemistry - Herein, we report the synthesis of ZnO nanorod films onto FTO (fluorine-doped tin oxide) substrates using the solution-processed electrodeposition method....     

A note on the eigenvalues of p‐fractional Hardy–Sobolev operator with indefinite weight

In this article, we study the eigenvalues of p‐fractional Hardy operator where , , , and Ω is an unbounded domain in with Lipschitz boundary containing 0. The weight function V may change sign and may have singular points. We also show that the least positive eigenvalue is simple and it is uniquely associated to a nonnegative eigenfunction. Moreover, we proved that there exists a sequence of eigenvalues as .     

Impact of APCI ionization source in liquid chromatography tandem mass spectrometry based tissue distribution studies

Measurement of test article concentration in tissue samples has been an important part of pharmacokinetic study and has helped to co‐relate pharmacokinetic/pharmacodynamic relationships since the 1950s. Bioanalysis of tissue samples using LC–MS/MS comes with unique challenges in terms of sample handling and inconsistent analyte response owing to nonvolatile matrix components. Matrix effect is a phenomenon where the target analyte response is either suppressed or enhanced in the presence of matrix components. Based on previous reports electrospray ionization (ESI) mode of ionization is believed to be more affected by matrix components than atmospheric pressure chemical ionization (APCI) or atmospheric pressure photoionization. To explore the impact of ionization source with respect to bioanalysis of tissue samples, five structurally diverse compounds – atenolol, verapamil, diclofenac, propranolol and flufenamic acid – were selected. Quality control standards were spiked into 10 different biological matrices like whole blood, liver, heart, brain, spleen, kidney, skeletal muscle, eye and skin tissue and were quantified against calibration standards prepared in rat plasma. Quantitative bioanalysis was performed utilizing both APCI and ESI mode and results were compared. Quality control standards when analyzed with APCI mode were found to be more consistent in terms of accuracy and precision as compared with ESI mode. Additionally, for some instances, up to 20‐fold broader dynamic linearity range was observed with APCI mode as compared with ESI mode. As phospholid interferences have poor response in APCI mode, protein precipitation extraction technique can be used for multimatrix quantitation, which is more amenable to automation. The approach of multiple biological matrix quantitation against a single calibration curve helps bioanalysts to reduce turnaround time. Copyright © 2016 John Wiley & Sons, Ltd.     

Hamiltonian cycles in polyhedral maps

We present a necessary and sufficient condition for existence of a contractible, non-separating and non-contractible separating Hamiltonian cycle in the edge graph of polyhedral maps on surfaces. We also present algorithms to construct such cycles whenever it exists where one of them is linear time and another is exponential time algorithm.     

Syntheses of 1,5-Benzothiazepines-Part XXXI: Syntheses and Antimicrobial Studies of 10-Substituted-7- (monochlorophenyl/dichlorophenyl)-6H-6a,7-dihydro-6-phenyl[1]benzopyrano[3,4-c]-[1,5]benzothiazepines

Abstract

Two flavindogenides, 3-(2-chlorobenzylidene)-flavanone and 3-(2,4-dichloro- benzylidene)-flavanone reacted with six 5-substituted-2-aminobenzenethiols, the substituents being fluoro, chloro, bromo, methyl, methoxyl, and ethoxyl, to give respective 12 new compounds, 10-substituted-7-(2-chlorophenyl/2,4-dichlorophenyl)- 6H-6a,7-dihydro-6-phenyl[1]benzopyrano[3,4?c][1,5]benzothiazepines (5a–l) in 60–70% yields. The products were characterized on the basis of microanalytical data for elements and IR, ¹ H, and ¹³ C NMR and mass spectral studies. All the synthesized compounds were evaluated for their antimicrobial activity against the bacteria,Escherichia coli and GFC,and the fungi,Aspergillus niger, Aspergillus flavus,and Curvularia lunata.     

Thermodynamic investigation on M–Te–O (M = Sc, Y) system

The standard Gibbs energy of formation of M₂TeO₆ and M₆TeO₁₂ (where M = Sc, Y), was determined from its vapor pressure measurements by employing thermogravimetry-based transpiration technique. This technique was validated by measuring the vapor pressure of well-studied substances such as TeO₂(s) and CdCl₂(s). The temperature dependence of the vapor pressure of TeO₂(g) over the mixtures M₆TeO₁₂ + M₂O₃ (where M = Sc, Y), generated by the incongruent vaporization reaction, M₆TeO₁₂(s) → 3M₂O₃(s) + TeO₂(g) + ½O₂(g) were measured in the temperature range 1,413–1,473 K and 1,623–1,743 K for Sc₆TeO₁₂(s) and Y₆TeO₁₂(s), respectively. Similarly, the vapor pressure of TeO₂(g) over the mixtures M₂TeO₆(s) + M₆TeO₁₂(s) generated by the vaporization reaction, 3M₂TeO₆(s) → M₆TeO₁₂(s) + 2TeO₂(g) + O₂(g) was measured in the temperature range (1,223–1,293 K) and (1,333–1,423 K) for Sc₂TeO₆(s) and Y₂TeO₆(s), respectively. From the vapor pressure measurements, the standard Gibbs energy of formation of M₆TeO₁₂ and M₂TeO₆ were derived.