Analytical applications of picolinealdehyde salicyloylhydrazone: II. Extraction and spectrophotometric determination of vanadium(V)

Picolinealdehyde salicyloylhydrazone reacts with vanadium(V) to produce a yellow 1:1 complex (λ_max = 400 nm, ? = 2.17 × 10⁴ liters · mol^?1 cm^?1) in aqueous ethanolic solution. The yellow complex can be extracted into chlorobenzene (λ_max = 425 nm, ? = 2.16 × 10⁴ liters · mol^?1 cm^?1) and used for the spectrophotometric determination of trace amounts of vanadium. Interferences have been investigated. The method has been applied to the determination of vanadium in steel and in lead concentrates.     

The interplay of thio(seleno)amide/vinylogous thio(seleno)amide "resonance" and the anisotropic effect of thiocarbonyl and selenocarbonyl functional groups

Amino-substituted thio(seleno)acrylamides 1-4 were synthesized and their 1H and 13C NMR spectra assigned. Both the NMR data and the results of theoretical calculations at the ab initio level of theory were employed to elucidate the adopted structures of the compounds in terms of E/Z isomerism and s-cis/s-trans configuration. In the case of the asymmetrically N(Me)Ph-substituted compounds, ab initio GIAO-calculated ring current effects of the N-phenyl group were applied to successfully determine the preferred conformer bias. The restricted rotations about the two C-N partial double bonds were studied by DNMR and the barriers to rotation (DeltaG(c)++) determined at the coalescence temperatures, and these were discussed with respect to the structural differences between the compounds. The barriers to rotation were also calculated at the ab initio level of theory where the best results (R(2) = 0.8746) were obtained only with inclusion of the solvent at the SCIPCM-HF/6-31G* level of theory. The calculations also provided means of assessing structural influences which were not available due to inaccessible rotation barriers. By means of natural bond orbital (NBO) analysis of 1-4, the occupation numbers of nitrogen lone pairs and bonding/antibonding pi/pi orbitals were shown to quantitatively describe thio(seleno)amide/vinylogous thio(seleno)amide "resonance". Finally, the thio(seleno)carbonyl anisotropic effect was quantitatively calculated by the GIAO method and visualized by isochemical shielding surfaces (ICSS). Only marginal differences between the two anisotropic effects were calculated and are therefore of questionable utility for previous and future applications with respect to stereochemical assignments.     

Synthesis of novel thio(seleno) phosphate-phosphonates and their biological activities

In order to search for novel herbicides with high activity and selectivity, a series of thio(seleno) phosphate-phosphonate derivatives were synthesized in good yields by a one-pot procedure using tris(diethylamino)phosphine activated by iodine as the phosphorylating reagent. The structures of all compounds prepared were confirmed by spectroscopic methods and microanalyses. Preliminary bioassays indicated that some of the products possess potent and selective herbicidal activities and antiphytoviral activities against the tobacco mosaic virus (TMV). In addition, some of them exhibit significant fungicidal activities against R. Solani and P. Piricola. © 1998 John Wiley & Sons, Inc. Heteroatom Chem 9:369–375, 1998     

Analytical applications of the determination of hexacyanoferrate(III) with ascorbic acid: Part IV. Determination of hydroxylamine

Hydroxylamine can be determined by reaction with an excess of standard potassium hexacyanoferrate(III) solution at pH 8–10. After 30 min the excess is titrated with ascorbic acid solution in the presence of 2,6-dichlorophenolindophenol indicator.     

Analytical applications of 3-(2′-thiazolylazo)-2,6-diaminopyridine: Spectrophotometric determination of palladium

3-(2′-Thiazolylazo)-2,6-diaminopyridine reacts with palladium(II) in strongly perchloric acid media, to produce a blue 1:1 complex (λ_max = 665 nm, ? = 1.37 × 10⁴ liters · mol^?1 · cm^?1), which allows the spectrophotometric determination of 0.6 to 4.5 ppm of palladium. The method is applied to the determination of palladium in small samples of hydrogenation catalysts.     

Spectrophotometric determination of niobium(V) after extraction in the presence of thiocyanate with the ethylene-bis-(triphenylphosphonium) cation

Niobium(V) (0–20 μg) can be determined spectrophotometrically after its extraction as ethylene-bis- (triphenylphosphonium) thiocyanatoniobate(V) into chloroform. The effects of diverse ions and masking studies are reported. The system is applied to the determination of niobium in a range of steels.     

Oxidative cyclocondensation of thio(seleno)-amides and ureas 1. 2-thioxo-4-quinazolone

It has been found for the first time that 2-thioxo-4-quinazolone in the presence of acid catalysts in dimethyl sulfoxide is converted to8H,15H-1, 2, 4-thiadiazolo[3, 2-b:5, 4-b]diquinazoline-8,15-done. The reaction proceeds via oxidative cyclocondensation. The formation of this structure in preference to five other proposed isomers is substantiated using quantum-chemical methods.Institute of Plant Chemistry, Academy of Sciences of the Republic of Uzbekistan, Tashkent 700170. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 845–849, June, 1996. Original article submitted November 27, 1995.     

Structure and rearrangements of 3-Iso(thio,seleno)cyanato-1,2,3-triarylcyclopropenes

A series of new fluctional 3-iso(thio,seleno)cyanato-1,2,3-triarylcyclopropenes was synthesized. The structure of compounds was proved by ¹H and ¹³C NMR, IR, and mass spectra, and that of 3-(1,2,3-triphenylcyclopropenyl) isothiocycnate was confirmed by X-ray crystallography. In compounds under consideration by means of ¹H and ¹³C NMR was discovered and investigated a fast reversible migration of isocyanato, isothiocyanato, and isoselenocyanato groups along the perimeter of the theree-membered ring proceeding according to the dissociation-recombination mechanism.     

Analytical applications of thio-, seleno- and telluro-ethers-III spectrophotometric determination of palladium with dibenzyl selenide

Palladium chloride is very efficiently extracted with a benzene solution of dibenzyl selenide. The extract can be used to determine palladium spectrophotometrically in the range 0.38-3.00 ppm. Determination of palladium in presence of platinum metals and many cations and anions, is reported.     

Titrimetric determination of vanadium(IV) with DCTA

Vanadium(IV) has been determined by DCTA titration conductometrically, spectrophotometrically and visually (with Alizarin Red S, Gallein and Catechol Violet as indicators at pH 4.0, 4.2 and 4.5-4.6 respectively). The interference of nickel, copper, lead, aluminium and thorium can be removed, and the method utilized for the analysis of binary mixtures of vanadium(IV) with nickel, copper or thorium.     

Analytical applications of ternary complexes-VI Spectrophotometric determination of trace amounts of palladium

Extremely sensitive and specific colour reactions in both aqueous and organic solutions are described for the spectrophotometric determination of palladium(II) ions. The methods are based upon ternary complex formation with 1,10-phenanthroline or pyridine, and Rose Bengal Extra. Themolar absorptivities are 5 × 10⁴ (aqueous) and 1.25 × 10⁵ (organic) in the presence of a 1000-fold molar excess of EDTA as mass masking agent. Under these conditions there is negligible interference with the pyridine-Rose Bengal Extra system from the 22 cations (including silver, gold and platinum) and seven anions investigated. Both colour reactions take place within 15 min and the complexes are stable for long periods.     

New approach to preparation of N-acylphosphoramido(thio)(seleno)ates

N-[2-(X)-1,3,2-Oxathiaphospholane] derivatives (X = S, Se, O) of carboxamides were prepared and their DBU-assisted reaction with alcohols led to the corresponding O-alkyl-N-acylphosphoramido(thio)(seleno)ates. Their structures were confirmed by MS analysis and ¹H and ³¹P NMR spectroscopy. Independently N-acylphosphoramidoselenoates were converted to N-acylphosphoramidates by treatment with tert-butylperoxytrimethylsilane. The oxathiaphospholane approach was also applied to the synthesis of derivatives having N-prolylphosphoramido(thio)(seleno)ate linkages on the 5′-OH group of AMP.     

Oxidative cyclocondensation of cyclic thio(seleno)ureas. 4. Electronic effects of the substituents and the medium

We have studied the electronic effect of substituents, steric factors, the medium, and the nature of the oxidizing agent on oxidative cyclocondensation of 2-thioxo-4-quinazolone and its substituted derivatives. We have found that electron-donor substituents promote the reaction while electronacceptor substituents inhibit the reaction. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 616–622, April, 2006.     

Titrimetric determination of octacyanotungstate(IV) ions with N-bromosuccinimide

Summary N-Bromosuccinimide has been successfully applied in the determination of 1–50 mg of W(CN)₈ ^4–in approximately 6 M hydrochloric acid using Naphthol Blue Black indicator. The average error is ±0.42% and the average standard deviation is ±0.06 mg. The method is not applicable to the determination of Mo(CN) ₈ ^4– ions. Tetrakis-(N-hydro-2-carbocyclic acid-pyridinium)octacyanotungstate(IV) and -molybdate(IV) were used as primary standards for the preparation of standard Mo(IV) and W(IV) solutions. The composition of the latter compounds was verified by analysis and single crystal X-ray data were obtained.

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Titrimetrische Bestimmung von Octacyanowolframat(IV)-ionen mit N-Bromsuccinimid

Zusammenfassung N-Bromsuccinimid wurde mit Erfolg zur Bestimmung von 1–50 mg W(CN)₈ ^4–-Ionen in ungefähr 6 M Salzsäure mit Naphthol-Blau-Schwarz als Indicator verwendet. Der mittlere Fehler beträgt ±0,42 %, die mittlere Abweichung ±0,06 mg. Die Methode ist nicht brauchbar für die Bestimmung von Mo(CN)₈ ^4–-Ionen. Tetrakis(N-hydro-2-carbonylsäure-pyridinium) octacyanowolframat(IV) und -molybdat(IV) wurden als Primärstandards für die Herstellung von Standard-Mo(IV)- und -W(IV)-Lösungen benutzt. Die Zusammensetzung dieser Verbindungen wurde durch Analyse kontrolliert und die Einkristall-Röntgen-Daten wurden festgestellt.

     

Titrimetric determination of sodium dithionite with potassium hexacyanoferrate(III) as reagent and methylene blue as indicator

Summary A rapid titration procedure is recommended for the estimation of Na₂S₂O₄ in commercial sodium dithionite (sodium hydrosulphite, sodium hyposulphite) and in aqueous solutions of this compound, using potassium hexacyanoferrate(III) as reagent and methylene blue as indicator.With the procedure described there is no interference of decomposition products of dithionite (sulphate, sulphide, sulphite, trithionate, thiosulphate), additives (sodium chloride, phosphates, soda, EDTA, urea), methanol, ethanol, acetone or groundwood.For a commercial sodium hydrosulphite containing 91% of Na₂S₂O₄ the standard deviation is 0,3% absolute (degrees of freedom 9).

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Zusammenfassung Na₂S₂O₄ wird in technischem Natriumdithionit und dessen Lösungen mit Kaliumhexacyanoferrat(III) unter Verwendung von Methylenblau als Indicator titriert. Zersetzungsprodukte des Dithionits (Sulfat, Trithionat, Sulfit, Thiosulfat, Sulfid), Zusätze (Kochsalz, Soda, Phosphate, ÄDTA, Harnstoff), Methanol, Äthanol, Aceton oder Holzschliff stören nicht. In einem technischen Natriumdithionit mit 91% Na₂S₂O₄ betrug die Standardabweichung 0,3% absolut (9 Freiheitsgrade).

     

Titrimetric determination of uric acid with manganese(IV) sulfate

A simple indirect titrimetric determination of uric acid with manganese(IV) sulfate has been proposed. The method is stoichiometric and accurate and can be conveniently adapted for the assay of urinary uric acid.     

Titrimetric determination of vanadium(V) and chromium(VI) alone and in mixtures with hydrazine sulphate in phosphoric acid media

Hydrazine sulphate is proposed as a primary standard reagent for the direct titrimetric determination of vanadium(V) and chromium(VI) alone and in mixtures with potentiometric and photometric end-points, in 9–12 M phosphoric acid medium. The methods proposed possess advantages over those currently available. The use of phosphoric acid as a reaction medium not only accelerates the hydrazine-vanadium(V) reaction very much but also makes it follow an accurate stoichiometric path.