The determination of organic nitro,nitroso and azo compounds with copper

An indirect gravimetric method for the determination of organic nitro, nitroso and azo compounds has been investigated. The amount of nitro, nitroso, and azo compound present is calculated from the loss in weight of copper metal during the reduction of the compound to the amine. Interferences are discussed in detail. No standard solutions are required and only commonly available equipment is used Accuracy is of the order of ± 0 5%     

Equilibrium studies of beta-diketoaryl azo compounds with cobalt(II), nickel(II) and copper(II)

The interactions of some beta-diketoaryl azo substituted compounds with Co(II), Ni(II) and Cu(II) are discussed. The non-protonated form of the ligand is the main complexing species. The stability constants have been evaluated. The effect of substituent groups on the complexing ability of the ligands is discussed.     

Delocalization of unpaired electron in copper(II) complexes with azo compounds

Conclusions Contact interaction of the unpaired electron of the copper atom with the two equivalent nitrogen atoms, attached directly to the copper atom, is accomplished in the inner complexes of copper(II) with bis(benzeneazo-p-cresol) derivatives.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2771–2773, December, 1973.The authors thank B. I. Stepanov for the supplied compounds.     

Hydrazine sulphate as reagent for titrimetric determination of vanadium(V) and chromium(VI)

Conditions have been developed for the direct titration of vanadium(V) and chromium(VI) with hydrazine sulphate, barium diphenylaminesulphonate being used as indicator and osmium tetroxide as catalyst.     

Reactions of aromatic nitro,nitroso, hydroxylamino azoxy,azo and hydrazo compounds with selenol

Relative reactivities of aromatic nitro, nitroso, hydroxylamino, azoxy, azo and hydrazo compounds in the reduction with RSe^? were found to fall in the following order :

     

Sequential titration of iron(II) and vanadium(IV) mixtures with cerium(IV) sulphate, with ferroins as indicators

The titration of vanadium(IV) with cerium(IV) sulphate, with nitroferroin as indicator, is proposed. Unlike ferroin, the indicator does not need a catalyst in this system. By suitable choice of experimental conditions iron(II) can be titrated first to a ferroin end-point and then vanadium(IV) to a nitroferroin end-point.     

Gas-chromatographic determination of organomercury(II) compounds

Gas chromatography has proved to be an invaluable technique not only for the identification and determination of organomercury(II) compounds but also for differentiating inorganically bound from organically bound mercury. It also offers a possible route for determining various inorganic species through their conversion into organomercury(II) compounds. These procedures and the chemical and instrumental problems associated with them are reviewed.     

Spectrophotometric determination of sulfite with soluble mercury(II) compounds

Sulfite ion reacts with mercury(II) ion in acid solution to form the mercury(I) ion. The reaction is rapid and quantitative. The mercury(I) ion absorbs at 237 nm with a molar

5. Beer's law Data for Sulfite Complexes of Covalent Mercury(II) Compounds

SO2 (ppm)	?HgCl2a	?HgBr2	?Hg(Ac)2b	?Hg(SCN)2
2.0	12,500	10,000	10,000	9,200
4.0	12,500	11,500	10,000	9,000
6.0	12,500	11,500	10,000	9,200
8.0	12,000	11,000	10,500	9,800

a

Molar absorptivity based on sulfite ion at 230 nm. Solution was 6.86 buffer.

b

Mercuric acetate solutions seemed to be somewhat unstable. absorptivity of about 25,000. The absorbance is linear over a range of approximately 0.5–5.0 ppm as SO₂. Covalent mercury(II) compounds form a complex with sulfite, Hg(SO₃)₂^2?, which absorbs at 230 nm and shows a linear response over a range of 1–8 ppm as SO₂.

     

Vanadium compounds in reductimetric titrations-III: Applications of vanadium(II)

Vanadium(II) sulphate is a versatile reductant; it can change its oxidation number by one, two, or three units, depending on the oxidation potential of the half-cell with which it reacts and on the mode of titration. The end-point of many of the reactions can be detected by means of indicators. A back-titration method is usually needed for the three-electron oxidation of vanadium(II).     

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.     

Voltammetric determination of zirconium using azo compounds

The Optimum oconditions for zirconium complexation with azo compounds are found. The applicability of Eriochrome Red B, Calcon, and Calcion to the voltammetric determination of zirconium, total Zr(IV) and Hf(IV), and Zr(IV) in the presence of Zn(II), Cu(II), Cd(II), Ni(II), or Ti(IV) is demonstrated. The developed procedures are used to determine zirconium in a terbium alloy and in an alloy for airplane wheel drums.     

Hydrolysis of acyloxy nitroso compounds yields nitroxyl (HNO)

Nitroxyl (HNO/NO(-)), the reduced form of nitric oxide, has gained attention based on its separate chemistry and biology from nitric oxide. The inherent reactivity of HNO requires new and mechanistically unique donors for the detailed study of HNO chemistry and biology. Oxidation of cyclohexanone oxime with lead tetraacetate yields 1-nitrosocyclohexyl acetate, whereas oxidation of oximes in the presence of excess carboxylic acid gives various acyloxy nitroso compounds. These bright blue compounds exist as monomers as indicated by their infrared, proton, and carbon NMR spectra, and X-ray crystallographic analysis reveals the nitroso groups possess a "nitroxyl-like" bent configuration. Hydrolysis of these compounds produces nitrous oxide, the dimerization and dehydration product of HNO, and provides evidence for the intermediacy of HNO. Both thiols and oxidative metal complexes inhibit nitrous oxide formation. Hydrolysis of these compounds in the presence of ferric heme complexes forms ferrous nitrosyl complexes providing further evidence for the intermediacy of HNO. Kinetic analysis shows that the rate of hydrolysis depends on pH and the structure of the acyl group of the acyloxy nitroso compound. These compounds relax pre-constricted rat aortic rings similar to known HNO donors. Together, these results identify acyloxy nitroso compounds as a new class of HNO donors.     

X-ray investigations on a homologous series of mesogenic azo compounds complexed with palladium (II)

The X-ray diffraction experimental data concerning a homologous series of p-alkyl-p'-alkoxy-azobenzene cyclopalladated chloro-bridged dimers, both as powder and monodomain samples, are reported. These results, compared with those obtained for the parent non-metallated materials, suggest a model for the molecular arrangement wherein the alkoxy and alkyl chains are roughly coplanar with the palladium-containing rigid core and, depending on the chain length, bent towards each other.     

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.     

Direct titrimetric determination of thiosulphate,sulphite and tin(II) with copper sulphate solution

Summary Standard copper sulphate solution has been successfully used for the direct titration of dilute solutions (0.05N) of thiosulphate, sulphite or tin(II) in presence of potassium iodide (5–7%) and starch. The method is sensitive and precise.

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Zusammenfassung Eine Standardlösung von Kupfersulfat läßt sich mit Erfolg für die direkte Titration verdünnter Lösungen (0,05N) von Thiosulfat, Sulfit oder Sn(II) in Gegenwart von 5–7% KJ und Stärke verwenden. Das Verfahren ist empfindlich und genau.

     

N-heterocyclic carbene (NHC)-catalyzed direct amidation of aldehydes with nitroso compounds

NHC-catalyzed direct amidation of aldehydes with nitroso compounds is a powerful method for the synthesis of N-arylhydroxamic acids. A variety of aryl, alkyl, alkenyl, and heterocyclic aldehydes were found to give excellent yields of the corresponding N-arylhydroxamic acids. This chemistry was also extended to the synthesis of chiral N-arylhydroxamic acids by kinetic resolution of alpha-branched aldehydes, a domino amidation-redox amination reaction of acrolein, and a three-component reaction for the synthesis of N-arylaziridines.     

Rapid methods for the determination of iron(II) and vanadium (IV) in mixtures

Summary Rapid and accurate methods have now been developed for the titrimetric determination of iron(II) and vanadium(IV) in mixtures, using potassium permanganate or cerium(IV) sulphate. Chromium(III) does not interfere with these determinations.The procedures will be found to be much easier than the existing procedures because (1) the titrations can be carried out at the room temperature with a visual end point and (2) only one reagent is used for the determination of iron(II) and iron(II) plus vanadium(IV).

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Zusammenfassung Es werden Vorschriften gegeben zur schnellen und genauen titrimetrischen Bestimmung von Eisen(II) und Vanadium(IV) in Gemischen mit Hilfe von Kaliumpermanganat- oderCer(IV)-sulfatlösung. Chrom(III) stört die Bestimmungen nicht. Die beschriebenen Verfahren haben gegenüber den bisher üblichen Methoden den Vorteil, daß die Titration bei Zimmertemperatur mit visueller Endpunktsbestimmung durchgeführt werden kann und daß nur ein Reagens zur Bestimmung von Eisen(II) sowie von Eisen(II) + Vanadium(IV) gebraucht wird.