Kinetics and mechanism of oxidation of some reducing sugars by diperiodatoargentate(III) in alkaline medium

Summary The kinetics of oxidation of d-glucose, d-galactose, d-fructose, d-ribose, d-arabinose, d-xylose and 2-deoxyd-glucose by diperiodatoargentate(III) (DPA) have been investigated in alkaline medium. The order of the reaction with respect to [DPA] is unity while the order with respect to [sugar] is < 1 over the concentration range studied. The rate increases with an increase in [OH ^–] and there is a marginal decrease in the rate with an increase in [IO _inf4 ^sup– ]. No significant dependence on ionic strength was found, but the rate increases with a decreasing dielectric constant. Formic acid and the corresponding aldonic acids were detected as the products of oxidation. The participation of the open chain form of the sugar and a mechanism involving the initial formation of a complex between the enediol of the sugar and Ag^III are proposed.     

Oxidation of cobalt(II) aminopolycarboxylate complexes by peroxomonophosphoric acid in acetate buffers. A kinetic study

Summary The kinetics of oxidation of the Co^II complexes [Co(edta)]^2– and [Co(hedta)]^– [H₄edta=ethylenediamine tetraacetic acid and H₃hedta=N-(2-hydroxyethyl)ethylenediamineN, N, N triacetic acid] by peroxomonophosphoric acid (PMPA) in acetate buffer were investigated spectrophotometrically. The reactions exhibit first order behaviour in each reactant and are markedly in hibited by H⁺. A plausible mechanism consistent with the observed results is proposed.     

Oxidation of divalent manganese by peroxodiphosphate in acetate buffers. A kinetic study

Bivalent manganese in oxidized to the tervalent state in 4.0–5.3 pH (acetate buffers) when treated with an excess of peroxodiphosphate (PDP). Kinetic evidence for the formation of a 11 complex between manganese(II) and PDP was obtained. The reaction exhibits first order dependence on [Mn(II)] and fractional order dependence on [PDP]. The reaction is markedly inhibited by H⁺ ions. A plausible mechanism consistent with the observed data is proposed.

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pH=4,0–5,3 (). (II) 11. [Mn(II)] []. H⁺ . , .

     

Spectrophotometric determination of palladium with 4-(2-pyridylazo)-resorcinol (PAR)

Summary A spectrophotometric method for the determination of palladium is described using 4-(2-pyridylazo)-resorcinol as reagent. The method involves the formation of two red coloured chelates of palladium-PAR at p_H 4.0 and 10.5 respectively. The colour reactions have sensitivity of 0.0085g cm^–2 and 0.0071g cm^–2 for logI ₀/I= 0.001. The effects of p_H, time, order of addition of reagents, temperature etc. have been investigated. The composition of the complexes (metalreagent) have been confirmed by two methods as 11 (at p_H 4.0) and 32 (at p_H 10.5).

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Zusammenfassung Eine spektrophotometrische Methode zur Palladiumbestimmung mit PAR [4-(2-Pyridylazo)-resorcin] wurde beschrieben. Zwei rotgefärbte Chelate werden bei p_H 4,0 bzw. 10,5 gebildet. Die Empfindlichkeit der beiden Reaktionen beträgt 0,0085 bzw. 0,0071g · cm^–2. Der Einfluß von p_H, Zeit, Reihenfolge der Reagenzien, Temperatur usw. wurde untersucht. Die Zusammensetzung der Komplexe entspricht dem Molverhältnis Pd: Reagens= =11 bei p_H 4,0 bzw. 32 bei p_H 10,5.

     

On the Convolution of a Finite Number of Analytic Functions Involving a Generalized Srivastava–Attiya Operator

The present paper gives several subordination results involving a generalized Srivastava–Attiya operator (defined below). Among the results presented in this paper include also a sufficiency condition for the convexity of the convolution of certain functions and a sharp result relating to the convolution structure. We also mention various useful special cases of the main results including those which are related to the Zeta function.     

Bimodal Functionality in a Porous Covalent Triazine Framework by Rational Integration of an Electron‐Rich and ‐Deficient Pore Surface

A porous covalent triazine framework (CTF) consisting of both an electron‐deficient central triazine core and electron‐rich aromatic building blocks is reported. Taking advantage of the dual nature of the pore surface, bimodal functionality has been achieved. The electron deficiency in the central core has been utilized to address one of the pertinent problems in chemical industries, namely separation of benzene from its cyclic saturated congener, that is, cyclohexane. Also, by virtue of the electron‐rich aromatic rings with Lewis basic sites, aqueous‐phase chemical sensing of a nitroaromatic compound of highly explosive nature (2,4,6‐trinitrophenol; TNP) has been achieved. The present compound supersedes the performance of previously reported COFs in both the aspects. Notably, this reports the first example of pore‐surface engineering leading to bimodal functionality in CTFs.     

Tuning Pore Polarization to Boost Ethane/Ethylene Separation Performance in Hydrogen-Bonded Organic Frameworks

Hydrogen-bonded organic frameworks (HOFs) show great potential in energy-saving C₂H₆/C₂H₄ separation, but there are few examples of one-step acquisition of C₂H₄ from C₂H₆/C₂H₄ because it is still difficult to achieve the reverse-order adsorption of C₂H₆ and C₂H₄. In this work, we boost the C₂H₆/C₂H₄ separation performance in two graphene-sheet-like HOFs by tuning pore polarization. Upon heating, an in situ solid phase transformation can be observed from HOF-NBDA(DMA) (DMA=dimethylamine cation) to HOF-NBDA , accompanied with transformation of the electronegative skeleton into neutral one. As a result, the pore surface of HOF-NBDA has become nonpolar, which is beneficial to selectively adsorbing C₂H₆. The difference in the capacities for C₂H₆ and C₂H₄ is 23.4 cm³ g⁻¹ for HOF-NBDA , and the C₂H₆/C₂H₄ uptake ratio is 136 %, which are much higher than those for HOF-NBDA(DMA) (5.0 cm³ g⁻¹ and 108 % respectively). Practical breakthrough experiments demonstrate HOF-NBDA could produce polymer-grade C₂H₄ from C₂H₆/C₂H₄ (1/99, v/v) mixture with a high productivity of 29.2 L kg⁻¹ at 298 K, which is about five times as high as HOF-NBDA(DMA) (5.4 L kg⁻¹). In addition, in situ breakthrough experiments and theoretical calculations indicate the pore surface of HOF-NBDA is beneficial to preferentially capture C₂H₆ and thus boosts selective separation of C₂H₆/C₂H₄.     

Structure and thermotropic phase behavior of fluorinated phospholipid bilayers: a combined attenuated total reflection FTIR spectroscopy and imaging ellipsometry study

Lipid bilayers consisting of lipids with terminally perfluoroalkylated chains have remarkable properties. They exhibit increased stability and phase-separated nanoscale patterns in mixtures with nonfluorinated lipids. In order to understand the bilayer properties that are responsible for this behavior, we have analyzed the structure of solid-supported bilayers composed of 1,2-dipalmitoyl- sn-glycero-3-phosphocholine (DPPC) and of a DPPC analogue with 6 terminal perfluorinated methylene units (F6-DPPC). Polarized attenuated total reflection Fourier-transform infrared spectroscopy indicates that for F6-DPPC, the tilt of the lipid acyl chains to the bilayer normal is increased to 39 degrees as compared to 21 degrees for native DPPC, for both lipids in the gel phase. This substantial increase of the tilt angle is responsible for a decrease of the bilayer thickness from 5.4 nm for DPPC to 4.5 nm for F6-DPPC, as revealed by temperature-controlled imaging ellipsometry on microstructured lipid bilayers and solution atomic force microscopy. During the main phase transition from the gel to the fluid phase, both the relative bilayer thickness change and the relative area change are substantially smaller for F6-DPPC than for DPPC. In light of these structural and thermotropic data, we propose a model in which the higher acyl-chain tilt angle in F6-DPPC is the result of a conformational rearrangement to minimize unfavorable fluorocarbon-hydrocarbon interactions in the center of the bilayer due to chain staggering.     

"Diversity oriented synthesis" of functionalized chiral tetrahydropyridines: potential GABA receptor agonists and azasugars from natural amino acids via a sequential Baylis-Hillman reaction and RCM protocol

The preparation of chiral tetrahydropyridine-4-carboxylates as isoguvacine analogues and azasugars with a tertiary stereocenter from L-amino acids via diastereoselective a Baylis-Hillman reaction of N-allyl-Boc alpha-aminal, followed by ring-closing metathesis and dihydroxylation sequences, is reported.     

Synthesis and crystal structure of a mixed valence heteropoly green compound, (PPh<Subscript>4</Subscript>)<Subscript>4</Subscript>[PMo<Subscript>12</Subscript>O<Subscript>40</Subscript>], and its use as a catalyst in olefin epoxidation

A green heteropolyblue compound, (PPh₄)₄[PMo₁₂O₄₀] · 3DMF(1), has been synthesized from MoO₃, H₂O₂ and H₃PO₄ in acetylacetone medium and crystallized from N,N-dimethylformamide. Compound 1 was characterized by analytical and spectroscopic methods, and X-ray structure analysis. The compound is a one-electron paramagnet and shows a featureless and cubic EPR spectrum with <g> = 1.95 in DMF glass. The complex shows a Mo(V)–Mo(IV) couple, which has been studied by cyclic voltammetric and coulometric methods. The compound acts as an efficient olefin epoxidation catalyst with H₂O₂ as oxidant and NaHCO₃ as co-catalyst. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.