Adsorptive stripping voltammetric analysis of 2,4,6-tri(2′pyridyl)-1,3,5-triazine at a mercury electrode

The redox behaviour of adsorbed species of 2,4,6-tri(2-pyridyl)-1,3-5-triazine (TPTZ) at the surface of a mercury electrode was examined using cycling voltammetry. Based on the adsorption and accumulation of TPTZ at the charged mercury surface cathodic adsorptive stripping voltammetry (CSV) is applied for the trace determination of TPTZ using a differential pulse (DP) technique. Experimental and operational parameters for the quantitative analysis of TPTZ are optimized and the detection limit was found to be 3×10^–9 mol/l. The effect of some interferences, e.g. organic compounds, cations and anions, are investigated.     

Adsorptive stripping voltammetric determination of traces of molybdenum in natural water in the presence ofα-benzoinoxime

The electrochemical behavior of the molybdenum complex of -benzoinoxime was investigated using cyclic voltammetry and linear scan voltammetry, after adsorptive accumulation of the complex onto a hanging mercury drop electrode (HMDE). The signal corresponds to the reduction of molybdenum in the complex adsorbed at the HMDE surface. Under optimal conditions, the adsorptive stripping voltammetric procedure gave an extremely low detection limit of 0.1 nM (9.6ng/l) Mo(VI) following stirred accumulation for 5 min at 0.0 V (vs. Ag/AgCl). The reduction cur rent-[Mo(VI)] relationships were linear up to 25 and 100 nM. Repetitive determinations of 10 nM solutions gave relative standard deviations of 2.2 and 3.5%, for 1 and 5-min accumulation periods, respectively. Most of the ions investigated did not interfere with the determination of molybdenum, except for tungsten. Excellent selectivity against copper was observed. The proposed procedure was applied to the direct determination of molybdenum in natural water.     

Copper–mercury film electrode for cathodic stripping voltammetric determination of Se(IV)

The copper-mercury film electrode has been suggested for the determination of Se(IV) in a wide range of concentration from 1x10(-9) to 1x10(-6) mol L(-1)by square-wave cathodic stripping voltammetry. Insufficient reproducibility and sensitivity of the mercury film electrode have been overcome by using copper(II) ions during the plating procedure. Copper(II) has been found to be reduced and form a reproducible copper-mercury film on a glassy carbon electrode surface. The plating potential and time, the concentration of copper(II) and the concentration of the supporting electrolyte have been optimised. Microscopy has been used for a study of the morphology of the copper-mercury film. It has been found that it is the same as for the mercury one. The preconcentration step consists in electrodeposition of copper selenide on the copper-mercury film. The relative standard deviation is 4.3% for 1x10(-6) mol L(-1) of Se(IV). The limit of detection is 8x10(-10) mol L(-1) for 5 min of accumulation.     

Hydrogenation of 6- and 7-alkyl-2-(4′-bromophenyl)indolizines

Hydrogenation of 6- and 7-alkyl-2-(4-bromophenyl)indolizines over rhenium heptasulfide proceeds with hydrodebromination to give a mixture ofcis- andtrans-isomers of 6- and 7-alkyl-2-phenylindolizidines.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1267–1268, July, 1993.     

Synthesis and NMR Analysis of N-Methyl-2-(4′-bromophenyl)morpholine Instructions for Students

Chemistry laboratory simulators have not been worth consideration until the CD-ROM came along with its wonderful capacities. Corel, [1] a well-known name in software has realized this. Their new ChemLab CD-ROM has excited some interest among chemistry teachers. This review examines the contents of this CD-ROM, rates the effectiveness of its experiments, and suggests who might profit from the use of such a simulator for the traditional chemistry laboratory.     

Fluorometric determination of aluminum using 1 -isonicotinoyl-2-(2′,4′-dihydroxy)benzylidene hydrazine

A fluorometric method for the determination of aluminum through complexation with 1-isonicotinoyl-2-(2′,4′-dihydroxy)benzylidene hydrazine is presented. The dependence of fluorescence efficiency on pH and ethanol/water ratios as well as the kinetics of complex formation are discussed. The detection limit at 20% RSD was observed to be 0.5 ppb (ng/ ml).     

Synthesis and properties of new functionalized poly(imides) based on 1,1-bis(4-aminophenyl)-1-z{4′-bis(4′’-bromophenyl)amino}phenyl-2,2,2-trifluoroethane

A new aromatic diamine, 1,1-bis(4-aminophenyl)-1-{4′-bis(4″-bromophenyl)amino}phenyl-2,2,2-trifluoroethane, is synthesized. Its interaction with various dianhydrides of aromatic carboxylic acids via high-temperature polycondensation yields a number of new functionalized poly(imides) combining high thermal and mechanical characteristics with solubility in organic solvents. The values of T _g vary from 208 to 230°C, and temperatures corresponding to 10% weight loss fall within the intervals 330–370 and 550–660°C (in air and argon, respectively). Spectroelectrochemical characteristics of poly(imides) are studied by cyclic voltammetry and UV-VIS spectrometry. Poly(imides) exhibit high reversible stability of electrochromic properties, and their color changes from colorless (the neutral form) to green (the oxidized form) as the applied potential is varied from 0 to 1.25 V.     

Spectrophotometric determination of acidity constants of 4-(2′-thiazolylazo)-resorcinol (TAR) in water-organic mixtures

<正>The acidity constants of TAR in different water-organic solvent binary mixtures at 25℃have been determined spectrophotometrically. DATa ANalysis(DATAN) program was used for calculations of the acidity constants and pure spectra of all formed species and their concentration distribution diagram in applied pH interval.Results show that there are a fairly inverse relationship between acidity constants and the mole fraction of the organic solvent in the binary mixtures.Effects of solvent composition on the pK_as and pure spectrum of each component are also discussed.     

Alkylation of 5-(3,3-R,R′-2-oxido-1-triazeneoxymethyl)tetrazoles

Russian Chemical Bulletin - Alkylation of 5-(3,3-R,R′-2-oxido-1-triazeneoxymethyl)tetrazole salts with iodomethane, dimethyl sulfate, chloroacetonitrile, and...     

Stereochemistry of the asymmetric reduction of (1′s)-1,3-dimethyl-4(1′-phenylethylimino)piperidine

The stereochemistry of the asymmetric reduction of the imine obtained from 1,3-dimethylpiperidin-4-one and (S)--phenylethylamine has been studied. It is shown that hydride reduction of imine 1 by sodium borohydride in methanol is asymmetric and gives the cis and trans diastereomeric pair 1,3-dimethyl-4-(-phenyl-ethylamino) piperidine in the ratio 3:1. Using sodium in isopropanol gives only one trans diastereomeric pair.¹H NMR has been used to identify the stereochemical structure and diastereomer excess of the cis and trans isomers of 1,3-dimethyl-4-(-phenylethylamino)piperidine which had been separated by column chromatography.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 219–221, February, 1996.     

Efficient Synthesis of 1-(4′-Methylbenzoyl)- 3,3-Diethylthiourea Under Microwave Irradiation Using Potassium Fluoride on Alumina

1,1-diethylthiourea and 4-methylbenzoic acid were condensed to 1-(4′-methylbenzoyl)-3,3-diethylthiourea in open vessels under microwave irradiation using an unmodified domestic microwave oven. The synthesis was carried out in the presence of alumina impregnated with potassium fluoride and catalytic amounts of N,N-dimethylformamide. The yields are noticeably improved in comparison with classical methods.     

Complexation equilibria and spectrophotometric determination of zinc (II) with 2-(4′-methyl-2′-thiazolylazo)-4,6-dimethylphenol

2-(4′-methyl-2′-thiazolylazo)-4,6-dimethylphenol has been synthesized and its acid—base behaviour (pK_a1=0.03 ± 0.01, pK_a2=9.70±0.09) and complexation equilibria with zinc (logβ₁₀₁=6.70±0.04, logβ₁₀₂ = 13.70±0.02) studied in a 40% (v / v) ethanol—water medium at I=0.25 M NaClO₄. A spectrophotometric method for the determination of 0.2–1.5 ppm of zinc has been developed (ε=1.83 × 10⁴ 1. mol⁻¹ cm⁻¹ at 590 nm) and applied to its determination in lubricating oils.     

Very sensitive differential pulse adsorptive stripping voltammetric determination of 4-nitrophenol at poly (diphenylamine)/multi-walled carbon nanotube-β-cyclodextrin-modified glassy carbon electrode

In this work, a glassy carbon electrode (GCE) modified with poly (diphenylamine)/multi-walled carbon nanotubes-β-cyclodextrin (PDPA/MWCNT-β-CD) film was constructed and used for the determination of 4-nitrophenol (4-NP). Diphenylamine was successfully electropolymerised onto MWCNT-β-CD-modified GCE by cyclic voltammetry in monomer solution and 5 mol L^?1 H₂SO₄. The surface morphology of PDPA/MWCNT-β-CD film was characterised using scanning electron microscopy and electrochemical impedance spectroscopy. After adsorption of 4-NP on PDPA/MWCNT-β-CD at 0.2 V for 150 s, it showed a well-defined reduction peak in phosphate buffer solution at pH = 7. The PDPA/MWCNT-β-CD film enhanced the reduction peak current due to the complex formation between β-CD and 4-NP, presence of conductive polymer film as electron transfer mediator and also ability of MWCNTs for strong adsorptive and catalytic effect. Peak current increased linearly with 4-NP concentration in the range of 0.1 to 13.9 µg L^?1. The detection limit was obtained as 0.02 µg L^?1, which is better than other reported detection limits for the determination of 4-NP. The results showed that modified electrode has good sensitivity and selectivity. This sensor was used for the determination of 4-NP in water samples.     

Synthesis of (−)-(1′S,4aS,8aR)- and (+)-(1′S,4aR,8aS)-4a-ethyl-1-(1′-phenylethyl)-octahydroquinolin-7-ones

A synthesis of the enamine (−)-(1′S)-5-ethyl-1-(1′-phenylethyl)-1,2,3,4-tetrahydropyridine 4 and its application in a synthesis of (−)-(1′S,4aS,8aR)- and (+)-(1′S,4aR,8aS)-4a-ethyl-1-(1′-phenylethyl)-octahydroquinolin-7-ones 5 and 6 is described. In addition, an X-ray study of 6 is reported. Finally, the preparation of (+)-(4aS,8aR)-4a-ethyl-octahydroquinolin-7-one 7 is described.     

Synthesis of poly(2,2′,3,3′-indole)

New approaches to the synthesis of poly(2,2′,3,3′-indole) were developed based on the photochemical dehydropolycondensation of indole in the presence of iodine and the photochemical polycondensation of 1-(1H-indol-3-yl)-2-iodo-1-ethanone in the absence of catalyst and solvent. A suggested mechanism for the formation of the oligomeric chain in these reactions includes the intermediate formation of 3,3′-diindole with subsequent polycondensation via elimination of hydrogen atoms at position 2 of the dimer pyrrole fragment.     

Water-Promoted Synthesis of 3,3′-Di(indolyl)oxindoles

The reaction of isatin and indoles in refluxing water/ethanol (7:3) affords 3,3′-di(indolyl)oxindoles in excellent yields.     

Cathodic stripping voltammetric determination of β-cyfluthrin,a pyrethroid insecticide,using polished silver solid amalgam electrode

Journal of Solid State Electrochemistry - This work describes an electroanalytical procedure for determination of beta-cyfluthrin (βCF), a pyrethroid insecticide, using polished silver solid...