A new PVC matrix membrane sensor for determination of praseodymium(III) ion based on bis(salicylaldehyde)thiocarbohydrazone as an ion carrier

The sufficient amounts of bis(salicylaldehyde) thiocarbohydrazone (STCH) as a lipophilic selective element (3%, w/w), sodium nitrobenzene (NB) as a plasticizer (64%, w/w), tetraphenyl borate (NaTPB) as an anionic additive (3%, w/w), and poly vinyl chloride (PVC) as a polymeric matrix (30%, w/w) was employed to form a PVC membrane of a new Pr³⁺ ions selective sensor to apply as an indicator electrode in analytical applications. The best electrode response was observed in the slope (19.5 ± 0.7 mV per decade) over a wide concentrations from lower (1.0 × 10^?6 mol L^–1) to higher (1.0 × 10^?2 mol L^–1) of Pr³⁺ ion solution with a detection limit of 8.5 × 10^–7 mol L^–1. This electrode showed the fast response time about 10 second for praseodymium ion concentration range of 1.0 × 10^–6 to 1.0 × 10^–2 mol L^–1, in the pH range of 2.3–7.9. The matched potential method was applied to study the selectivity of electrode toward Pr³⁺ ions in comparison with many common cations. The results showed the negligible disturbance of all other cations on the proposed praseodymium(III) electrode. The making sensor has been employed successfully as an indicator electrode in the potentiometric titration of praseodymium(III) solution with EDTA at pH 6.0. Moreover the applicability of the sensor was studied in determination of Pr³⁺ ion in mixtures of different ions.     

A review on potential development of flame retardant kenaf fibers reinforced polymer composites

Kenaf fibers have been extensively explored from the past few decades in polymer composites industries owing to its extensive adaptations, excellent properties together with its comparable mechanical properties to traditional glass fibers polymer composites. The combustibility or lowered flame retardancy hampered the diverse applications of kenaf fibers reinforced polymer composites, as it affects the mechanical strength and stiffness of composites during fire. Current review article intended to be a comprehensive source of published literature involving the flame retardants (FRs), types and applications of FRs and the fabrication of kenaf fibers reinforced polymer composites. This article will also provide a perfect data on the recent development of the FR kenaf fibers polymer composites with different FRs and explored its structural and semi‐structural industrial application for performing further research in this topic. Copyright © 2016 John Wiley & Sons, Ltd.     

Radical Cyclisation of α‐Halo Aluminium Acetals: A Mechanistic Study

α‐Bromo aluminium acetals are suitable substrates for Ueno–Stork‐like radical cyclisations affording γ‐lactols and acid‐sensitive methylene‐γ‐lactols in high yields. The mechanistic study herein sets the scope and limitation of this reaction. The influence of the halide (or chalcogenide) atom X (X=Cl, Br, I, SPh, SePh) in the precursors α‐haloesters, as well as influence of the solvent and temperature was studied. The structure of the aluminium acetal intermediates resulting from the reduction of the corresponding α‐haloesters has been investigated by low‐temperature ¹³C‐INEPT diffusion‐ordered NMR spectroscopy (DOSY) experiments and quantum calculations, providing new insights into the structures of these thermally labile intermediates. Oxygen‐bridged dimeric structures with a planar Al₂O₂ ring are proposed for the least hindered aluminium acetals, while monomeric structures seem to prevail for the most hindered species. A comparison against the radical cyclisation of aluminium acetals derived from allyl and propargyl alcohols with the parent Ueno–Stork has been made at the BHandHLYP/6‐311++G(d,p) level of theory, highlighting mechanistic similarities and differences.     

Immobilized copper(II) on nitrogen‐rich polymer‐entrapped Fe3O4 nanoparticles: a highly loaded and magnetically recoverable catalyst for aqueous click chemistry

A heterogeneous magnetic copper catalyst was prepared via anchoring of copper sulfate onto multi‐layered poly(2‐dimethylaminoethyl acrylamide)‐coated magnetic nanoparticles and was characterized using various techniques. The catalyst was found to be active, effective and selective for one‐pot three‐component reaction of alkyl halide, sodium azide and alkyne, known as copper‐catalyzed click synthesis of 1,2,3‐triazoles. As little as 0.3 mol% of catalyst was found to be effective under the optimum conditions. The catalyst could also be recycled and reused up to seven times without significant loss of activity. Thermal stability, high loading level of copper on catalyst, broad diversity of alkyl/benzyl/allyl bromide/chloride and alkyl/aryl terminal alkynes without isolation of azide intermediate, and good to excellent yields of products make this procedure highly economical. Copyright © 2015 John Wiley & Sons, Ltd.     

Microdetermination of phenols, carboxylic acids and phenolic acids by potentiometric and visual titrations in dimethylformamide

Potentiometric titration of phenols with sodium methoxide in dimethylformamide, with a glass-calomel electrode system, is limited to monohydric phenols substituted with electron-attracting groups and dihydric phenols in which the two -OH groups are substituted in isolated benzene rings. Brilliant Orange has proved to be a suitable indicator in the titration of all types of mono- and dihydric phenols. Titan Yellow is recommended as indicator for the titration of carboxylic acids. Simultaneous visual titration of -OH and -COOH groups is also described. A detailed study with 62 structurally different compounds covering the various groups is reported, and a suitable procedure for the microdetermination of each class of these compounds with an error of +/- 0.2% absolute or less is presented.     

Structural,theoretical and multinuclear NMR study of mercury(II) complexes of phosphorus ylides: Mono and binuclear complexes

Reaction of phosphorus ylide Ph₃PCHC(O)C₆H₄Cl (Y₁) with HgX₂ (X = Cl, Br and I) and ylide (p-tolyl)₃PCHC(O)CH₃ (Y₂) with HgI₂ in equimolar ratios using methanol as solvent leads to binuclear products. The bridge-splitting reaction of binuclear complex [(Y₁) · HgCl₂]₂ by DMSO yields a mononuclear complex containing DMSO as ligand. O-coordination of DMSO is revealed by single crystal X-ray analysis in mononuclear complex of [(Y₁) · HgCl₂ · DMSO]. C-coordination of ylides is confirmed by X-ray structure of binuclear complex [(Y₂) · HgI₂]₂. Characterization of the obtained compounds was also performed by elemental analysis, IR, ¹H, ³¹P, and ¹³C NMR. Theoretical studies on mercury(II) complexes of Y₁ show that formation of mononuclear complexes in DMSO solution in which DMSO acts as a ligand, energetically is more favorable than that of binuclear complexes.