Die Oxydationswirkung von Natrium-1,2-naphthochinon-4-sulfonat

Zusammenfassung Die Reaktionen von Natrium-1,2-naphthochino-4-sulfonat mit -Aminosäuren, primären aliphatischen Aminen, Dicarbonsäuren, aliphatischen -Hydroxysäuren und primären Alkoholen werden beschrieben. In allen diesen Fällen reagiert Natrium-1,2-naphtochinon-4-sulfonat als Oxydationsmittel und wird zu dem entsprechenden Diphenol reduziert.     

Ion exchangers as catalysts. II. Catalytic decomposition of hydrogen peroxide with resin-ethylenediamine-copper(II) complex ions

Summary The slow decomposition of H₂O₂ in the presence of Dowex-50 W resin in the form of an ethylenediaminecopper(II) complex ion in water is accompanied by an induction period. The reaction is first order with respect to [H₂O₂] and the rate constant (perg of dry resin) was deduced. Autocatalytic behaviour was found for the H₂O₂ decomposition with 2% crosslinked divinylbenzene. The induction period disappeared and the reaction rate increased when the decomposition was carried out with a resin in the form of a peroxo-copper complex, which proves that the formation of an intermediate (active species) retards the reaction rate. The precursor of the active species, formed during the induction period, was not the amine-copper(II) complex ion but a product of the latter with H₂O₂. It proved impossible to carry out the decomposition in acid or buffer solutions, in which the resin is regenerated.     

Organotin polymers—I. Copolymerization parameters of tributyltin methacrylate with methyl methacrylate,propyl methacrylate and butyl methacrylate

The monomer reactivity ratios for radical copolymerizations of tributyltin methacrylate (monomer-1) with methyl methacrylate, propyl methacrylate and butyl methacrylate have been found as r₁ = 0.79 and r₂ = 1.0, r₁ = 0.58 and r₂ = 0.9, and r₁ = 0.65 and r₂ = 0.68 respectively.     

Chemometric Assisted UV-Spectrophotometric Methods Using Multivariate Curve Resolution Alternating Least Squares and Partial Least Squares Regression for Determination of Beta-Antagonists in Formulated Products: Evaluation of the Ecological Impact

In this study, UV-spectrophotometry coupled with chemometrics has been utilized to enhance the sustainability of quality control analysis of beta antagonists. First, we developed and optimized two eco-friendly chemometric-assisted methods without preliminary separation utilizing (1) multivariate curve resolution alternating least squares (MCR-ALS) and (2) well-established partial least squares regression (PLSR) multivariate calibration for the resolution and quantification of the most commonly prescribed beta antagonists in active pharmaceutical ingredients or commercial pharmaceutical products. The performance of the two proposed chemometric methods was computed and compared. Second, a comprehensive qualitative and quantitative evaluation of the eco-friendliness of the developed methods was performed utilizing the following greenness assessment tools: Green Analytical Procedure Index (GAPI), Analytical Eco-scale assessment (AES) tool, Raynie and Driver’s assessment tool and Analytical GREEnness Metric (AGREE). The models showed satisfactory recovery with a range from 99.83% to 101.12% for MCR-ALS and from 99.66% to 101.54% for PLSR. The optimized models were employed for green analysis of the investigated beta-blockers in single or co-formulated formulations without prior separation. The predictivity of the proposed MCR-ALS and the well-established PLSR method were very comparable. Nevertheless, the MCR-ALS method has the ability to recover the pure spectra of the studied analytes and the interferences as well. The proposed chemometric methods are fast, precise and do not need any sample pretreatment. In addition, they can be used as a benign substitute for the traditional methods used for the analysis of the investigated drugs in pharmaceutical products without harmful impacts on human health and the environment. They also provide advantages in terms of low solvent usage, reduced energy consumption and short analysis time, making them a safe and sustainable approach for quality control analysis.     

Synthesis,magnetic and spectral studies of iron(III) and cobalt(II,III) complexes of 4-formylantipyrine N(4)-substituted thiosemicarbazones

The synthesis and characterization of complexes of iron(III), cobalt(II) and cobalt(III) with 4-formylantipyrine N(4)-methyl-, N(4)-dimethyl-, and 3-piperidylthiosemicarbazones are reported. Elemental analyses, molar conductivities, magnetic measurements and spectral (i.r., electronic and e.s.r.) studies have been used to elucidate the nature of the metal complexes. The i.r. spectra show that the thiosemicarbazones behave as bidentate or tridentate ligands, either in the thione or thiolato form. Different stereochemistries are proposed for the various cobalt(II) complexes on the basis of spectral and magnetic studies. This revised version was published online in June 2006 with corrections to the Cover Date.     

Kinetic and mechanistic investigations on the oxidation of N’-heteroaryl unsymmetrical formamidines by permanganate in aqueous alkaline medium

Kinetic studies on the oxidation of two substituted azinyl formamidines (Azn-Fs), namely N,N-dimethyl-N’-(pyrimidin-2-yl) formamidine (Pym-F) and N,N-dimethyl-N’-(pyridin-2-yl) formamidine (Py-F), by alkaline permanganate have been performed by spectrophotometry. The spectroscopic and kinetic evidence reveals the formation of 1:1 intermediate complexes between the oxidant and substrates. The influence of pH on the oxidation rates indicated that the reactions are base-catalyzed. The reactions show identical kinetics, being first order each in [MnO₄ ^?]₀ and [Azn-F]₀, but with a fractional first-order dependence on [OH^?]. The effect of temperature on the reaction rate has been studied. Increasing ionic strength has no significant effect on the rate. The final oxidation products of Pym-F and Py-F were identified as 2-aminopyrimidine and 2-aminopyridine, respectively, in addition to dimethyl amine and carbon dioxide. Under comparable experimental conditions, the oxidation rate of Py-F is higher than that of Pym-F. A reaction mechanism adequately describing the observed kinetic behavior is proposed, and the reaction constants involved in the different steps of the mechanism have been evaluated. The activation parameters with respect to the rate-limiting step of the reactions, along with thermodynamic quantities, are presented and discussed.     

Manufacturing of pH sensitive PVA/PVP/MWCNT and PVA/PEG/MWCNT nanocomposites: an approach for significant drug release

The purpose of this paper is studying the effect of incorporation of Multiwall Carbon Nanotubes (MWCNT) into two different nanocomposites in poly vinyl alcohol (PVA)/polyvinylpyrrolidone (PVP), and PVA/Polyethylene glycol (PEG). MWCNT were synthesized by chemical vapor deposition (CVD) method using acetylene and Fe/Co/Al₂O₃ as carbon precursor and catalyst, respectively. Nitric acid and sulfuric acid were used for purification and functionalization of MWCNT. Afterward, highly pure and functionalized MWCNT (0, 0.02, and 0.05% w/w) were incorporated in PVA/PVP and PVA/PEG to synthesize PVA/PVP/MWCNT and PVA/PEG/MWCNT nanocomposites hydrogel membranes that cross-linked by freezing–thawing. PEG and PVP were selected in these nanocomposites as dispersion matrix for MWCNT as well as for increasing the elasticity of the nanocomposites membranes. The morphology of the hydrogels was characterized by SEM, FTIR, XRD, TGA, and the mechanical properties of the hydrogel membranes were investigated. The swelling behavior in different pH-buffer solutions was studied as well as studying weight loss percentage and swelling kinetic. The drug releasing process of the hydrogel membranes was investigated using salicylic acid as a model drug. It was found that MWCNT are dispersed well into the polymers and crystallinity, mechanical properties and thermal stability of the hydrogels contain MWCNT are better than that without MWCNT. Maximum degree of swelling was observed at pH 7 and swelling degree increases with increasing the ratio of MWCNT in the hydrogels from 0.02 to 0.05%. All hydrogel membranes followed non-Fickian mechanism and drug releasing were controlled by varying the pH and amount of MWCNT.     

New pyranosyl cembranoid diterpenes from Sarcophyton trocheliophorum

During our continual searching programme for novel bioactive metabolites from Sarcophyton trocheliophorum, collected from Red Sea, we describe herein the isolation and structural elucidation of further two new pyrane-based cembranoid diterpenes: 9-hydroxy-7,8-dehydro-sarcotrocheliol (1) and 8,9-expoy-sarcotrocheliol acetate (2), along with the well-known sarcotrocheliol acetate (3), (+)-sarcophine (4), (+)-sarcophytoxide (5) and (-)-sarcophytoxide (6). The chemical structures of compounds 1 and 2 were determined on the basis of 1D and 2D NMR (¹H, ¹³C, ¹H–¹H COSY, HMQC, HMBC and NOE), mass spectra (ESI and HR-ESIMS) and by comparison with related structures. The antimicrobial activities of the reported compounds 1–6 were investigated. According to the molecular docking study of compounds 1–6 using 3D structure of α,β tubulin in complex with taxol (PDB code 1JFF) and epothilone A (PDB code 1TVK), sarcophine (4) displayed the highest affinity towards both crystal structures, followed by 5 and 6, meanwhile pyrane-based cembranoid diterpenes (1–3) showed less affinity.