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Abstract  

A simple method for labelling of 16-Br-hexadecanoic acid (16-BrHDA) with radioactive iodine has been reported via nucleophilic131I-for-Br exchange in the dry state and in organic solvents. While preparation in some organic solvents such as acetic acid, dimethyl formamide (DMF) and dimethyl sulfoxide (DMSO) required reaction times of more than 2 hours to give yields of 20–50%, halogen exchange in dry state at temperature of about 100 °C gave rise to yields of about 94% of radiochemically pure 16-131IHDA within 5 min. The labelling product could be purified by high performance liquid chromatography (HPLC) and was shown to be free of significant radiochemical impurities.

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Abstract  

This article is dedicated to develop an experimental approach for directly visualizing the global freezing phase change behavior of micro liquid droplets. The infrared (IR) thermograph was proposed to image the basic solidification phenomena of droplet and to acquire its temperature variations during the transient process. In particular, the volumetric recalescence event, regarded as initiation of freezing, was revealed by IR images for the first time. Preliminary results demonstrated that the involved temperature transition due to release of the latent heat can be accurately characterized by evident color break in IR images. Further, experiments were also performed simultaneously on three kinds of droplets made of pure water, dimethylsulfoxide (DMSO) and nano liquid to grasp more precise temporal and spatial temperature distribution. Types of the occurring solidification and the initial frozen volume produced from the recalescence were generally discussed. The IR monitoring method suggests a straightforward way for detecting the freezing phase change activity and its temperature evolution at micro scale.

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Abstract  

Liquid-liquid extraction of divalent palladium by solutions of Diesel oil (D.O.) and gas oil II (G.O.II) in benzene and lacquer petroleum from nitrate media has been studied. Palladium in concentrations of ∼10−3M is very effectively extracted by dilute solutions of extraction reagents and the distribution of palladium is almost independent of the acidity and nitrate concentration of the aqueous phase. Of other common salts, chlorides, thioeyanates and nitrites affect the palladium distribution. In many cases high concentrations of salts completely suppress the extraction of palladium. The rate of palladium extraction by dilute solutions of extractants is relatively small. Some substances such as dimethyl sulfoxide (DMSO) were found to accelerate the extraction. Palladium extraction from nitric acid media also has been studied from the points of view of chemical and radiation stability. Diesel oil was found to be a more stable extraction reagent in acid media than gas oil II.

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Abstract  

The effect of -radiation on the electronic absorption spectra of the negatively solvatochromic dyestuff1, namely, 4-(4-N,N,-dimethylaminostyryl)-pyridinium methiodide in water and dimethylsulphoxide solvents is investigated. Ionizing radiation at different absorbed doses brought about gradual bleaching of aerated dye solutions. The -radiation-induced degradation and the consequent changes in the electronic absorption spectrum of dye 1 are discussed in the light of the theoretically calculated spectrum. The linear response range of dye1 in case of DMSO solution is wider than that in H2O. The results demonstrate that the radiochromic dye solution offer dosimetry in the low dose range by means of visible spectrophotometric analysis.

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Journal of Thermal Analysis and Calorimetry
Authors: K. Siimer, P. Christjanson, T. Kaljuvee, T. Pehk, I. Lasn, and I. Saks

Abstract  

The thermal behaviour of MUF resins from different suppliers with different content of melamine was studied, along with the 13C NMR spectroscopic analysis of resin structure and the testing of particleboards in current production at Estonian PB factory Pärnu Plaaditehas AS. The chemical structure of resins from DMSO-d6 solutions was analysed by 13C NMR spectroscopy on a Bruker AMX500 NMR spectrometer. The melamine level in different MUF resins is compared by the ratios of carbonyl carbon of urea and triazine carbon of melamine in 13C NMR spectra. Curing behaviour of MUF resins was studied by stimultaneous TG-DTA techniques on the Labsys™ instrument Setaram. The shape of DTA curves characterisises the resin synthesis procedure by the extent of polymerisation of UF and MF components and is in accordance with structural data.

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Transition metal complexes with thiosemicarbazide-based ligands

31. Dioxouranium(VI) complexes with N(1),N(4)-bis(salicyIidene)- and N(1)-benzoylisopropylidene-N(4)-saIicylidene-S-alkyl-isothio-semicarbazides

Journal of Thermal Analysis and Calorimetry
Authors: V. Leovac, E. Ivegeš, K. Szécsényi, K. Tomor, G. Pokol, and S. Gal

Abstract  

Solvate complexes of UO2 2+ andN(1), N(4)-bis(salicylidene)-S-methylisothiosemicarbazone, (H2Me-L1), of general formula [UO2(Me-L1)S] (S= H2O, MeOH, EtOH, Py, DMF and DMSO) were synthesized. The methanolic UO2 2+” adducts of N(1)-benzoylisopropylidene-N(4)-salicylidene-S-alkylisothiosemicarbazone, (H2R-L2,R=Me, Prn) of general formula [UO2(R-L2)· MeOH], were also prepared. Thermal decomposition of the complexes was investigated in air and argon. The complexes decompose to α-U3O8 in air, while in argon the decomposition is not completed up to 1000 K. The temperature and the mechanism of decomposition of the complexes are a function of the solvent belonging to the inner coordination sphere.

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Abstract  

The paper describes the synthesis of low molecular mass poly(allyl chloride) (PAC) (M n= 856-3834 g mol-1) using Lewis acid (ALCL3, FeCL3, TiCL4) and al powder. Branching in PAC was indicated on the basis of elemental analysis and 1H-NMR spectroscopy. azidation of pac could be carried out at 100°C by using NaN3 and DMSO as solvent. Curing of poly(allyl azide) (PAA) by cyclic dipolar addition reaction with EGDMA (ethylene glycol dimethacrylate, 5-45 phr) was investigated by differential scanning calorimetry and structure of cured polymer was confirmed by FTIR. A two-step mass loss was exhibited by uncured and cured PAA in nitrogen atmosphere. A mass loss of 20-28% (155-274°C) and 50-61% (330-550°C) was observed.

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Journal of Flow Chemistry
Authors: Sofie Seghers, Frederik E.A. Van Waes, Ana Cukalovic, Jean-Christophe M. Monbaliu, Jeroen De Visscher, Joris W. Thybaut, Thomas S.A. Heugebaert, and Christian V. Stevens

Despite extensive research into peptide synthesis, coupling of amino acids with weakly nucleophilic heterocyclic amines remains a challenge. The need for microwave technology to promote this coupling interferes with the scalability of the process. By applying the microwave-to-flow paradigm, a library of (α-aminoacyl)amino-substituted heterocycles was continuously produced at near quantitative conversions and the reaction was scaled up successfully. Various N-Cbz-protected amino acids were activated using BtH/SOCl2 under continuous-flow conditions with excellent yields. Their coupling with heterocyclic amines was accomplished in MeCN—NMP on a preparative scale. However, performing both steps in-line resulted in an inconvenient work-up. Therefore, a two-step approach was taken, isolating the intermediate Bt-activated amino acid via simple filtration. This allows for a solvent switch to DMSO for the coupling reaction which led to excellent conversions for a broad range of substrates.

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Rod-shaped nanocrystals are formed by self assembly of t -Bu-phenyl substituted tetra(carboxamido)perylenes (BPP) in different solvents. The structure and the dimensions of the nano-rods may be controlled by the choice of the hydrogen-bond accepting capacity of the solvent (DMSO, DMF, DMAc, HMPA), by the concentration and by the composition of solvent-mixture (by adding hydrogen-bond donating solvents), but is independent of the surface used for their deposition (mica, silicon, gold, glass). The different forms of aggregation were examined by AFM and SNOM and were correlated to UV-Vis absorption spectra of the aggregates in solution. The orientation of the transition dipole moment of the molecules in the nanocrystals has been determined by polarized fluorescence microscopy and, in combination with the crystal structure of the t -Bu substituted analogue of BPP, is used to develop a model for the internal molecular structure of the rod shaped aggregates.

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Transition-metal complexes with hydrazides and hydrazones

7. Dioxomolybdenum(VI) complexes of salicylaldehydep-hydroxybenzoylhydrazone and their thermal stability

Journal of Thermal Analysis and Calorimetry
Authors: I. Ivanović, K. Andjelković, V. M. Leovac, Lj. Klisarov, M. Lazarević, and D. Minić

Several new complexes of dioxomolybdenum(VI) of the general formula [MoO2(L)S], whereL is the dianion of salicylaldehydep-hydroxybenzoylhydrazone andS denotes H2O, MeOH, py, PPh3, DMSO or DMF, were synthesized and characterized by elemental analysis, electronic UV-VIS and IR spectra, thermal analysis, molar conductivity and magnetic susceptibility measurements. Salicylaldehydep-hydroxybenzoylhydrazone participates in the coordination as a tridentate ligand with the ONO set of donor atoms. The complexes contain acis-MoO2 group and are of octahedral geometry. Complexes of the MoO2L type were also prepared by synthesis in CHCl3 solution and by isothermal heating of [MoO2(L)S] complexes. The MoO2L complex synthesized in CHCl3 solution has most probably a pentacoordinated structure while the complex obtained by isothermal heating of [MoO2(L)S] has a polymeric hexacoordinated structure.

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