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131.
The polarographic behaviour of salicylaldehyde-2-pyridylhydrazone (SAPH) has been studied in aqueous buffer solution containing 40% ethanol using DC and DP polarographic methods. In the pH range 1.8–7.5 the observed single irreversible reduction wave is assigned to the splitting of the N-N bond and reduction of C=N centre. In alkaline medium, a second wave appears at a more negative potential due to the reduction of the salicylaldehyde which is formed by hydrolytic decomposition of the SAPH molecule. The effect of pH on the limiting current andE
1/2 as well as the reduction mechanism are discussed and compared with similar compounds. The kinetic parameters of the electrode reaction have been calculated.The analytical properties of the copper(II)-SAPH system is described. The complex gave rise to a single irreversible well-defined wave (E
1/2=–0.58 V at pH=5.2). The reaction process is diffusion controlled. A method is suggested for the determination of Cu(II) in presence of different metal ions as the difference in theirE
1/2 values is sufficient for the purpose.This work is taken partly from the M. Sc. Thesis of Jamal S. Shalabi 相似文献
132.
Besma Lajmi Mourad Hidouri Mongi Ben Amara 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(11):i156-i158
The crystal structure of tripotassium pentairon hexaphosphate has been determined by single‐crystal X‐ray diffraction. The structure contains one Fe atom on a center of symmetry, one K, two Fe and two P atoms on twofold axes, and one Fe, two P and one K atom in general positions. The K3Fe5(PO4)6 structure consists of a complex three‐dimensional framework of corner‐sharing between iron polyhedra, and corner‐ and edge‐sharing between PO4 tetrahedra and iron polyhedra (FeO5 and FeO6). This linkage between iron and phosphorus forms intersecting channels containing the K atoms. 相似文献
133.
Two synthetic routes to a novel class of sterically overcrowded alkenes, bithioxanthylidene crown ethers 1, are described. The 1H spin-lattice relaxation times (T1) of the crown ethers as well as those of the corresponding complexes with Li+, Na+, K+, Rb+ and Cs+ in CDCl3 were measured and the results were interpreted in terms of complexation affinities. 相似文献
134.
Conway B Hevia E Kennedy AR Mulvey RE Weatherstone S 《Dalton transactions (Cambridge, England : 2003)》2005,(8):1532-1544
Synthesised either by an unusual tert-butyl metathesis between tert-butyllithium and a n,s-butylmagnesium amide or by reaction of an alkyl Grignard reagent and a sodium amide, five tert-butylmagnesium amides, Bu(t)MgDBA (5)(DBA=dibenzylamide), Bu(t)MgDA (6)(DA=diisopropylamide), Bu(t)MgHMDS (7)(HMDS=1,1,1,3,3,3-hexamethyldisilazide), Bu(t)MgTMP (8)(TMP=2,2,6,6-tetramethylpiperidide) and Bu(t)MgNCy2 (9)(cy=cyclohexyl) have been isolated as crystalline solids. All five amides have been characterised by X-ray crystallography and solution NMR spectroscopic studies. The former studies reveal a common dimeric molecular structure with amido bridges in a planar (MgN)2 ring and terminal Bu(t) ligands on the Mg atoms. Also described is the dodecameric primary amide [Bu(n)MgN(H)Dipp]12 (10a) and its monomeric solvate Bu(n)MgN(H)Dipp.TMEDA (10b)(Dipp=2,6-diisopropylphenyl; TMEDA=N,N,N',N'-tetramethylethylenediamine). The crystal structures of the oxo-insertion products Bu(t)MgOBu(t).THF (11), Bu(t)Mg(mu-OBu(t))(mu-TMP)MgTMP (12) and Mg(OBu(n))HMDS.solv [solv=THF (13a) or Et2O (13b)], made fortuitously during the course of this work, are also presented. 相似文献
135.
Schiff-Base complexes of bis-5-phenylazosalicylaldehyde ethylenediimine and bis-5-phenylazosalicylaldehyde-O-phenylenediimine ligands with Co(II) (I and II) have been synthesized and characterized by their IR spectra and elemental analyses. These complexes catalyze the oxidation of styrene in the presence of dioxygen and excess pyridine. The effect of the reaction conditions on the oxidation of styrene was studied by varying solvent, nature and amount of the catalyst and substrate. The catalytic behavior of the studied complexes was shown to be dependent on the conditions applied. In all reactions, acetophenone and 1- phenylethanol were the only observed products. 相似文献
136.
The new thermotropic polyester/polyaniline (PIn/PAni) blends have been prepared by solution blend of synthesized liquid crystalline poly[4,4′‐bis (ω‐alkoxy) biphenylisophthalate]s having four and six methylene units in spacer (PI4 and PI6) with PAni doped with camphorsolfonic acid (CSA). The percolation threshold electroactivity of prepared blend films has been determined by cyclic voltammetry. The effect of the PAni concentration, solvent nature and polyester structure on the electroactivity of the blends has been investigated. The extremely low percolation threshold of prepared PIn/PAni‐CSA blends from dimethylformamide (DMF) and m‐cresol solution was 3% weight of PAni‐CSA. The amount of conducting polymer necessary to retard the formation of the liquid crystalline (LC) phase is up to 45% by weight. Phase behavior studies by differential scanning calorimetry and polarizing microscopy show that blends with 45% of conducting polymer are both liquid crystal and conductive. The morphology of the blends has been investigated by scanning electron microscopy. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
137.
Syed A. Ali Mohammed A. Siddiqui and Mohammed A. Ali 《Reaction Kinetics and Catalysis Letters》2005,87(1):199-206
Summary A parametric study of catalytic reforming process in a pilot plant was carried out by varying the pressure, H2/HC ratio, and space velocity. The results show that lower aromatics and higher hydrogen yields can be accomplished by increasing
the space velocity in existing reformers, which will also result in better C5+yield. 相似文献
138.
Nonlinear and nonequilibrium electrophoresis of spherical particles of radius a is shown to be possible when the solid surface allows field or current penetration. At low particle Peclet numbers, transient capacitative charging occurs until the surface polarization completely screens the external field. For a DC applied field [see text], the resulting electrokinetic velocity reaches Dukhin's maximum value of [formula: see text], where [see text] and mu are the liquid permittivity and viscosity. At high Peclet numbers, electroosmotic convection of the electroneutral bulk stops the transient charging before complete field-line exclusion. For an ion-selective and conducting spherical granule, the polarization is then determined by the steady-state Ohmic current driven by the penetrated external field. The high-Peclet electrokinetic velocity is lower, diffusivity-dependent and scales as [see text]. 相似文献
139.
Leita BA Moubaraki B Murray KS Smith JP Cashion JD 《Chemical communications (Cambridge, England)》2004,(2):156-157
The dinuclear iron(II) complex [(pypzH)(NCSe)Fe([micro sign]-pypz)(2)Fe(NCSe)(pypzH)].2H(2)O displays a single, sharp spin crossover transition between the [HS-HS] and [LS-LS] states and is structurally characterised above and below the T(1/2)= 225 K value 相似文献
140.
S. S. Abd El Rehim L. I. Ali N. H. Amin N. F. Mohamed 《Monatshefte für Chemie / Chemical Monthly》1997,128(3):245-254
Summary The electrochemical behaviour of lead in NaOH solution was studied by potentiodynamic and cyclic voltammetric techniques in combination with X-ray diffraction analysis. The active dissolution of lead involves a small shoulderA1 followed by a peakA1 prior to a passive region. The shoulderA1 is assigned to the electroformation of a Pb(OH)2 film, whereas peakA1 is due to the formation of PbO. Beyond the passive region, the current density increases again, forming a small shoulderA2 and a peakA2 prior to the oxygen evolution potential. The shoulderA2 and the peakA2 are correlated to the electrooxidation of PbO to Pb3O4 and PbO2, respectively. The intensity of the anodic peaks increases with increasing alkali concentration, temperature and scan rate. In cyclic voltammetry, the reverse scan shows two cathodic peaksC1 andC2 which are correlated to the electroreduction of PbO and PbO2 respectively, to Pb.
Potentiodynamisches und cyclovoltammetrisches Verhalten einer Bleielektrode in NaOH-Lösung
Zusammenfassung Das elektrochemische Verhalten von Blei in NaOH wurde mittels potentiodynamischer und cyclovoltammetrischer Techniken unter Zuhilfenahme der Röntgenbeugungsanalyse untersucht. Die aktive Auflösung von Blei verläuft über eine SchulterA1, die von einem einer passiven Region vorgelagerten PeakA1 gefolgt wird. Die SchulterA1 wird der elektrochemischen Bildung eines Pb(OH)2-Films, der PeakA1 der Bildung von PbO zugeschrieben. Jenseits der passiven Region steigt die Stromdichte wieder an, und vor Erreichen des Sauerstoffpotentials treten eine kleine SchulterA2 und ein PeakA2 auf, die mit der Elektrooxidation von PbO zu Pb3O4 und PbO2 korrelieren. Analog dazu beobachtet man in der cyclischen Voltammetrie zwei kathodische PeaksC1 undC2, die der Elektroreduktion von PbO und PbO2 zu Pb entsprechen. Die Intensität der anodischen Peaks steigt mit steigender Alkalikonzentration, Temperatur und Scangeschwindigkeit.相似文献