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971.
《Electroanalysis》2004,16(16):1311-1317
The determination of some toxic metals by stripping chronopotentiometry with a supporting solution having an unconventional composition has been investigated with the aim of using such components in disposable measuring cells preservable in dry state and quite ready for use, only needing addition of a small volume of sample. The new supporting solution is prepared with a solid strong acid, p‐toluenesulfonic acid, in the place of the inorganic acids commonly used to improve the cation availability. The other components are, as usual, sodium chloride, which fixes the potential of the screen‐printed silver – silver chloride reference electrode, and mercury(II) chloride as the plating agent. This supporting solution has been tested in batch measurements with the mercury film glassy carbon electrode as well as with screen‐printed carbon‐ink electrodes, either with mercury film or bare. The physical shape of the mercury layer electrolytically deposited on screen‐printed carbon‐ink electrodes from a supporting solution containing 0.1 M p‐toluenesulfonic acid and 0.1 M sodium chloride has been investigated by scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS) microanalysis. In chronopotentiometric stripping p‐toluenesulfonic acid performs as well as the usual inorganic strong acids, particularly in terms of sensitivity. At 0.1 mol dm?3 it proved very suitable for the determination of toxic metals, in particular lead(II), at levels down to a few μg dm?3. The overall results appear promising and can open new avenues for preparing disposable cells for on‐field stripping chronopotentiometric determination of toxic metals. 相似文献
972.
We have examined two-dimensional electrophoresis (2-DE) gel maps of polypeptides from the Gram-negative bacterium Methylococcus capsulatus (Bath) and found the same widespread trains of spots as often reported in 2-DE gels of polypeptides of other Gram-negative bacteria. Some of the trains of polypeptides, both from the outer membrane and soluble protein fraction, were shown to be generated during the separation procedure of 2-DE, and not by covalent post-translational modifications. The trains were found to be regenerated when rerunning individual polypeptide spots. The polypeptides analysed giving this type of trains were all found to be classified as stable polypeptides according to the instability index of Guruprasad et al. (Protein Eng. 1990, 4, 155-161). The phenomenon most likely reflects conformational equilibria of polypeptides arising from the experimental conditions used, and is a clear drawback of the standard 2-DE procedure, making the gel picture unnecessarily complex to analyse. 相似文献
973.
Sheng Hua Liu 《Journal of organometallic chemistry》2003,683(2):331-336
Treatment of [Ru(CHCHCH2PPh3)X(CO)(PPh3)2]+ (X=Cl, Br) with KTp (Tp=hydridotris(pyrazolyl)borate) and NaBPh4 produced [TpRu(CHCHCH2PPh3)(CO)(PPh3)]BPh4. Reaction of RuHCl(CO)(PPh3)3 with HCCCH(OEt)2 produced Ru(CHCHCH(OEt)2)Cl(CO)(PPh3)2, which reacted with KTp to give TpRu(CHCHCHO)(CO)(PPh3). Treatment of [TpRu(CHCHCH2PPh3)(CO)(PPh3)]BPh4 with NaN(SiMe3)2 and benzaldehyde produced TpRu(CHCHCHCHPh)(CO)(PPh3). The later complex was also produced when TpRu(CHCHCHO)(CO)(PPh3) was treated with PhCH2PPh3Cl/NaN(SiMe3)2. The bimetallic complex [TpRu(CO)(PPh3)]2(μ-CHCHCHCHC6H4CHCHCHCH) was obtained from the reaction of [TpRu(CHCHCH2PPh3)(CO)(PPh3)]BPh4 with NaN(SiMe3)2 and terephthaldicarboxaldehyde. 相似文献
974.
The reaction of N-(3,4-dichlorophenethyl)-N-methylamine (1) with 3-chloromethyl-5-phenyl-1,2,4-oxadiazole (2) was investigated. Employment of an equimolar amount of 1 and 2 in the presence of potassium carbonate led to the expected tertiary amine 3 (N-[(3,4-dichlorophenyl)ethyl]-N-methyl-N-[(5-phenyl-1,2,4-oxadiazol-3-yl)methyl]amine), whereas an excess of 1 and prolonged reaction time resulted in ring fission of the oxadiazole system in 3 and finally in the formation of N′-benzoyl-N-[(3,4-dichlorophenyl)ethyl]-N-methylguanidine (4) and N,N′-bis[(3,4-dichlorophenyl)ethyl]-N,N′-dimethylmethanediamine (5). The structures of products 3–5 were determined by means of 1H and 13C NMR-spectroscopy, mass spectrometry and IR-spectroscopy, for 3 (as picrate) and 4 also X-ray structure analysis was employed. A possible mechanism of the reaction pathway leading to compounds 4 and 5 is proposed. 相似文献
975.
The new unsymmetrical N‐bridgehead, apo (zeromethine), mono‐methine, dimethine, meso substituted tetramethine and styryl cyanine dyes incorporating pyrazolo (4,5‐b) indolizine (benzoindolizine) nuclei were prepared. Structural confirmation was carried out by elemental analyses, IR, H‐NMR, mass spectra and 13C‐NMR with the aid of carbon DEPT spectral data. The visible absorption spectra for the newly synthesized cyanines were examined in 95% ethanol. 相似文献
976.
Some new N‐glycosides of 4‐(2‐phenylethyl)‐5‐pyridyl‐1,2,4‐triazole‐3‐thiones were synthesised by the coupling reaction of halo sugar with 4,5‐disubstituted 3H‐1,2,4‐triazole‐3‐thiones in the presence of mercuric cyanide and dry nitromethane as solvent, followed by deprotection using dry ammonia in methanol. All of the above compounds were fully characterized by means of infrared, 1H NMR spectroscopy, mass spectroscopy and elemental analysis. 相似文献
977.
Yu‐Hsiang Hu Chuh‐Yung Chen 《Journal of polymer science. Part A, Polymer chemistry》2002,40(21):3692-3702
The bulk polymerization of methyl methacrylate initiated with 2‐pyrrolidinone and n‐dodecyl mercaptan (R‐SH) has been explored. This polymerization system showed “living” characteristics; for example, the molecular weight of the resulting polymers increased with reaction time by gel permeation chromatographic analysis. Also, the polymer was characterized by Fourier transform infrared spectroscopy, 1H NMR, and 13C NMR techniques. The polymer end with the iniferter structures was found. By the initial‐rate method, the polymerization rate depended on [2‐pyrrolidinone]1.0 and [R‐SH]0. Combining the structure analysis and the polymerization‐rate expression, a possible mechanism was proposed. n‐Dodecyl mercaptan served dual roles—as a catalyst at low conversion and as a chain‐transfer agent at high conversion. Finally, the thermal properties were studied, and the glass‐transition temperature and thermal‐degradation temperature were, respectively, 25 and 80–100 °C higher than that of the azobisisobutyronitrile system. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3692–3702, 2002 相似文献
978.
A novel membrane sensor for selective monitoring of iodide, consisting of a triiodide‐ketoconazole ion pair complex dispersed in a PVC matrix, plasticized with a mixture of 2‐nitrophenyl octyl ether and dioctylphtalate with unique selectivity toward iodide ions, is described. The influence of membrane composition, pH of test solution and foreign ions on the electrode performance were investigated. The optimized membrane demonstrates a near‐Nernstian response for iodide ions over a wide linear range from 1.0 × 10?2 to 1.0 × 10?5 M, at 25 ± 1 °C. The electrode could be used over a wide pH range 3–10 and has the advantages of high selectivity, fast response time and good lifetime (over 4 months). It was successfully used as indicator electrode in potentiometric titrations and direct potentiometric assay of iodide ions. 相似文献
979.
Zois Syrgiannis 《Tetrahedron letters》2006,47(17):2961-2964
The thermodynamic parameters, ΔΔH# and ΔΔS#, were determined for the interception of an intermediate, with the structural characteristics of an aziridinium imide, by nucleophilic solvents during the reaction of 2-methyl-2-butene with N-phenyltriazolinedione. The experimentally measured parameters were found to be in favor of an SN2-‘like’ transition state and showed strong dependence on the bulkiness of the incoming molecule of the nucleophile-solvent. 相似文献
980.
Emmanuel Blas Patricio-Rangel Margarita Tlahuextl Hugo Tlahuext Antonio Rafael Tapia-Benavides 《Acta Crystallographica. Section C, Structural Chemistry》2020,76(4):322-327
The synthesis and characterization of two new 1,3,5‐triazines containing 2‐(aminomethyl)‐1H‐benzimidazole hydrochloride as a substituent are reported, namely, 2‐{[(4,6‐dichloro‐1,3,5‐triazin‐2‐yl)amino]methyl}‐1H‐benzimidazol‐3‐ium chloride, C11H9Cl2N6+·Cl? ( 1 ), and bis(2,2′‐{[(6‐chloro‐1,3,5‐triazine‐2,4‐diyl)bis(azanediyl)]bis(methylene)}bis(1H‐benzimidazol‐3‐ium)) tetrachloride heptahydrate, 2C19H18ClN92+·4Cl?·7H2O ( 2 ). Both salts were characterized using single‐crystal X‐ray diffraction analysis and IR spectroscopy. Moreover, the NMR (1H and 13C) spectra of 1 were obtained. Salts 1 and 2 have triclinic symmetry (space group P) and their supramolecular structures are stabilized by hydrogen bonding and offset π–π interactions. In hydrated salt 2 , the noncovalent interactions yield pseudo‐nanotubes filled with chloride anions and water molecules, which were modelled in the refinement with substitutional and positional disorder. 相似文献