Nicotinamidoxime as an analytical reagent

Summary Uranium (VI) has been found to give a yellow colour with nicotinamidoxime in alkaline medium which is highly satisfactory for the spectrophotometric estimation of the metal. The optimumph for development of the colour is 10.9–11.5 in presence of a large excess of the reagent, at 10–40C. The colour intensity is measured at 400 m. Sensitivity is 0.045 g uranium per cm², with a visual identification limit of 5 g uranium per ml. Beer's law is obeyed in the range of 5–40 ppm of the metal with an optimum range of 8–40 ppm. The colour is stable for at least one hour. All the common anions are without effect, excepting however, phosphate, carbonate, and cyanide which are tolerated only in traces. Use of tartrate or EDTA helps to mask effectively all the interfering cations excepting copper, iron and vanadium.     

Solochrome violet R.S. as a new colorimetric reagent

Summary Solochrome violet R.S. has proved to be a sensitive colorimetric reagent for the microdetermination of vanadium in the limits of 0.05 to 6 ppm with a sensitive filter photometer or a spectrophotometer, at 580 nm. A large number of cations up to 100 fold the vanadium amount do not interfere with its determination. The present work comprises a comparative study on the behaviour of solochrome violet and Fast Grey, based upon the great similarity in the molecular structure of the two dyes and the influence of the orthonitrophenolic group in the molecule of Fast Grey.Part I: See Z. analyt. Chem. 178, 184 (1960).     

Salicylhydroxamic acid as an analytical reagent

Summary Salicylhydroxamic acid has been used as a colorimetric reagent for the estimation of uranium, vanadium, molybdenum and iron. It permits the direct estimation of vanadium in presence of molybdenum and uranium, though iron interferes, while the estimation of uranium or molybdenum is not possible in presence of each other or of vanadium. The vanadium complex can be removed from solution by extraction with ethyl acetate and estimated colorimetrically between p_H 0.8 to 3.5. This permits its determination in steels after removal of iron. Sensitivity: U 0.1 g, V 0.017 g, Mo 0.015 g, Fe 0.0125 g.     

Redox and antimicrobial studies of transition metal(II) tetradentate Schiff base complexes

Neutral tetradentate chelate complexes of Cu^II, Ni^II, Co^II, Mn^II, Zn^II and VO^II have been prepared in EtOH using Schiff bases derived from acetoacetanilido-4-aminoantipyrine and 2-aminophenol/2-aminothiophenol. Microanalytical data, magnetic susceptibility, i.r., u.v.–vis., ¹H-n.m.r. and e.s.r. spectral techniques were used to confirm the structures of the chelates. Electronic absorption and i.r. spectra of the complexes suggest a square-planar geometry around the central metal ion, except for VO^II and Mn^II complexes which have square-pyramidal and octahedral geometry respectively. The cyclic voltammetric data for the Cu^II complexes in MeCN show two waves for copper(II) copper(III) and copper(II) copper(I) couples, whereas the VO^II complexes in MeCN show two waves for vanadium(IV) vanadium(V) and vanadium(IV) vanadium(III) couples. The e.s.r. spectra of the Cu^II, VO^II and Mn^II complexes were recorded in DMSO solution and their salient features reported. The in vitro antimicrobial activity of the investigated compounds was tested against the microorganisms such as Salmonella typhi, Staphylococcus aureus, Klebsiella pneumoniae, Bacillus subtilis, Shigella flexneri, Pseudomonas aeruginosa, Aspergillus niger and Rhizoctonia bataicola. Most of the metal chelates have higher antimicrobial activity than the free ligands.     

Glykosylazide als Ausgangsbasis zur Gewinnung von Nucleosidanalogen, 3. Mitt. Synthese von Alkylaminotetrazol- und Uretidinonnucleosiden

The -ribofuranosylazide1 is transformed after usual derivatization by suitable protecting groups into the P–N-ylid2, which gives the corresponding N-Glykosyl-N-alkylcarbodiimides4 and a small amount of the glykosylisocyanatde-rivative3 by reaction with alkylisocyanates. The carbodiimides4 were reacted with hydrazoic acid to give the alkylaminotetrazolnucleosides5 and finally the free nucleosidanalogs6. In the case of5 c the 5-aziridinyltetrazolnucleosid5 h was formed by an usual neighbouring group reaction. In addition the compound1 is transformed into the 3,5-diprotected anchor derivative7 by reaction withTIPSCl₂. The latter could be transformed by usual steps into the alkylaminotetra-zolnucleosides8 with a free 2-OH group. In the next step the 2-p-tolylthiocarbo-nates9 were prepared followed by transformation to the 2-desoxynucleosides10 by means of tributyltinhydride. Finally the free 2-desoxynucleosides11 were prepared. By reacting the carbodiimides4 with phenylisocyanate a mixture of the two possible regiouretidinonnucleosidderivatives12 and13 are formed. In the case of the N-glykosyl-N-allylcarbodiimide4 d only the one isomer13 d arises.

Herrn Prof. Dr.A. Neckel mit den besten Wünschen zum 60. Geburtstag gewidmet.     

Differential pulse voltammetric methods for the simultaneous estimation of uranium-iron and uranium-cadmium mixtures in solution

Differential pulse voltammetric methods have been developed for the simultaneous estimation of the constituents of uranium-iron and uranium-cadmium mixtures in solution. A mixture of 1M H₃PO₄–1M KH₂PO₄ (with a pH1.5), was found to be the most ideal supporting electrolyte for both methods, among many that were evaluated for their suitability. In uranium-iron mixtures the calibration for iron was found to be linear up to 150 g ml^–1 (r²=0.9986), while that of uranium up to 500 g ml^–1 (r²=0.999). Iron at 6.7 g ml^–1 level could be determined in the presence of 800 fold uranium (wt/wt) without significant interference. Uranium at 21 g ml^–1 level could be analyzed with 5-fold iron (wt/wt). This upper limit of iron was due to the precipitation of iron as phosphate. In the case of uranium — cadmium mixtures, cadmium calibration for cadmium was found to be linear up to 1300 g ml^–1 (r²=0.9993). Concentration levels of 4.6 g ml^–1 Cd could be determined at a 500-fold excess (wt/wt) of uranium. Uranium calibration was linear up to 500 g ml^–1 (r²=0.999) and 21 g ml^–1 uranium could tolerate up to a 1000-fold excess of cadmium (wt/wt). Both procedures could tolerate 10 g ml^–1 levels of metal ions, such as chromium, copper, manganese, molybdenum and vanadium.     

Selective and sensitive extraction spectrophotometric method for the determination of vanadium (V) as a mixed ligand complex withN-phenyl benzohydroxamic acid and 4-(2-pyridylazo)resorcinol in non-aqueous media

A selective, sensitive and direct method for the spectrophotometric determination of vanadium in steels is developed in which vanadium is extracted withN-phenyl benzohydroxamic acid (PBHA) into chloroform from 5M hydrochloric acid medium followed by colour development by addition of 4-(2-pyridylazo)resorcinol (PAR) inN,N-dimethyl formamide (DMF). The vanadium(V)-PBHA-PAR mixed ligand complex shows maximum absorbance at 560 nm with a molar absorptivity 3.6 × 10⁴ l mol^–1 cm^–1 and obeys Beer's law up to 2.0 g/ml of vanadium. The composition of the mixed ligand complex is determined by Job's method of continuous variations which revealed a 1 1 1 ratio for V(V) PBHA PAR. This method can be directly applied for the determination of vanadium in steels, while in the case of titanium base alloys, after separation of titanium matrix it gives good results even at 50–200 g of vanadium per gram level.     

Extraction-spectrophotometric determination of trace iron (II) in sea water with 2-[2-(3,5-dibromopyridyl)azo]-5-diethylaminobenzoic acid

An extraction-spectrophotometric method is described for the determination of traces of iron(II) with 2-[2-(3,5-dibromopyridyl)azo]-5-diethyl-aminobenzoic acid. The reagent forms a stable and blue 12 iron/reagent complex that can be extracted into chloroform. The apparent molar absorptivity of the iron(II) complex is 1.09 × 10⁵ 1 mol^–1 cm^–1 at 624 nm in chloroform. The reagent is relatively selective; interferences from cobalt, copper, nickel and vanadium can be removed by using dimethylglyoxime and EDTA. The method is applied to the determination of iron (II) in sea water and aluminium alloys with good precision and accuracy.     

Organically Templated Vanadium Oxide Phases: Synthesis and Structures of [H3NCH2CH2NH3][V2O6] and [HN(CH2CH2)3NH][VV2VIV4O14]·H2O

The synthesis and crystal structures of [H₃NCH₂CH₂NH₃][V₂O₆] (1) and [HN(CH₂CH₂)₃NH][V^V ₂V^IV ₄O₁₄]·H₂O (2) are described. The structure of the oxidized compound 1 consists of parallel stacks of vanadium oxide chains of corner sharing {VO₄} tetrahedra. The chains are stabilized by extensive hydrogen bonding involving oxide ligands of the chains and ethylenediammonium ions which fill the space between the stacks of chains. The structure of compound 2 consists of vanadium oxide layers separated by doubly protonated 1,4-diazabicyclo[2.2.2]octane and lattice water. The vanadium oxide layers, containing mixed-valence vanadium (V^V and V^IV) centers, are composed of zigzag ribbons of edge-sharing {VO₅} square pyramids interconnected by {VO₄} tetrahedra. Crystal data. C₂H₁₀N₂O₆V₂ , 1: monoclinic, space group P2₁/c (No. 14), a=5.5359(5), b=12.9430(12), c=5.6856(5) Å, =90, =97.460(2), =90°, V=403.93(6) ų, Z=2. A total of 2506 reflections ( _max=27.89°) was collected, of which 954 were used to resolve the structure. The structure was solved by direct methods and least-squares refinement converged at R=0.0592. C₆H₁₆N₂O₁₅V₆, 2: monoclinic, space group C2 (No. 5), a=19.303(4), b=6.667(2), c=7.579(2) Å, =90, =111.31(2), =90°, V=908.4(4) ų, Z=2. A total of 1779 reflections was collected, of which 1591 unique reflections were used for structural elucidation. The structure was solved by direct methods and least-squares refinement converged at R=0.0314.     

Geochemical study of trace vanadium in water by preconcentrational neutron activation analysis

By preconcentrational neutron activation analysis, trace vanadium was determined in natural water samples such as ground water, river water, lake water and so on. Preconcentration was accomplished by adsorption of vanadium on activated carbon surfaces using 8-quinolinol as an adjunct. As an analytical line, the 1434 keV -photopeak of⁵²V (T _1/2=3.75 m) produced in the⁵¹V (n,) ⁵²V reaction was measured with a conventional -ray spectrometer. The present analytical results show that the vanadium contents in natural water range widely from several tens ppt to about 100 ppb. A relatively larger amount of vanadium was observed in the ground water samples from the locations with basaltic soils or rocks, for example, around Mt. Fuji. This suggests that the geochemical interactions of ground water with such soils or rocks could enhance the vanadium concentrations. As an application, the vanadium contents were measured in the lake water from the five lakes surrounding Mt. Fuji in order to clarity geochemical and geological behaviors of natural water by probing vanadium as an indicator.     

Indirect Spectrophotometric Determination of Vanadium(IV) by Flow Injection Analysis Based on the Redox Reaction with Copper(II) in the Presence of Neocuproine

Abstract

An indirect photometric method with a continuous-flow analysis is presented for the determination of trace amounts of vanadium(IV). It is based on the redox reaction of copper(II) with vanadium(1V) in the presence of neocuproine. In the presence of neocuproine, copper(I1) is reduced easily by vanadium(I V) to a copper(1)-neocuproine complex, which shows a n absorption maximum at 454 nm. By measuring t h e absorbance of the complex at this wavelength, vanadium(1V) in t h e range 2×10^?6 - 8 × mol dm^?5 mol dm^?3 can be determined at a rate of 120 samples h^?1. The fractional determination of vanadium(1V) and iron(I1) is also studied.     

Alkyl ketoximes as analytical reagents. VIII

Summary A procedure is outlined for the quantitative separation ofg amounts of palladium from gram amounts of nickel, copper or iron in hydrochloric acid or hydrochloric and sulfuric acid solutions by the chloroform extraction of the 4-heptanone oxime complex of palladium(II) chloride. Using the outlined procedure approximately 0.2% of the copper, 0.06 % of the nickel and 0.05 % of the iron taken are co-extracted.

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Zusammenfassung Ein Verfahren zur quantitativen Trennung von Mikrogrammengen Pd von Grammengen Ni, Cu oder Fe in salzsaurer oder salzsauer-schwefelsaurer Lösung durch Chloroformextraktion des 4-Heptanonoxim-Pd(II)chlorid-Komplexes wurde angegeben. Dabei werden ungefähr 0,2% Cu, 0,06% Ni und 9,05% Fe mitextrahiert.

     

Spectrophotometric determination of trace amounts of iron(III) by extraction of mixed-ligand iron-tartrate-purpurin or iron-NTA-purpurin complex

Summary Spectropbotometric Determination of Trace Amounts of Iron(III) by Extraction of Mixed-Ligand Iron-Tartrate-Purpurin or Iron-NTA-Purpurin Complex A selective method is described for the determination of microgram amounts of iron(III) by means of its reaction at pH 9.0 with purpurin (1,2,4-trihydroxyanthraquinone) and tartrate or NTA and extraction into methyl isobutyl ketone. The molar absorptivity of the 112 iron(III)-auxiliary ligand-purpurin complex is 4.8×10⁴ 1·mole^–1·cm^–1 at 595 nm. Beer's law is obeyed from 0.05 to 0.25 ppm of iron in the aqueous phase. Procedures for determination of iron in tartrate or NTA medium, and fluoride-tartrate-NTA medium are given. The method is suitable for determining iron in Zn metal, W metal, NTA, drinking water, wines, urine and tartrates.     

Pyridine ketoximes as analytical reagents. XVI

Summary A procedure is described for spectrophotometric determination of trace amounts of cobalt in pure iron products with the reagent 2-pyridyl-2-thienyl--ketoxime. The sensitivity of the procedure is increased by the use of 4-cm cells. Beer's law is obeyed over the concentration range 0.05 to 0.600 p. p. m. The precision and accuracy of the method are reported and the effect of diverse ions is described. The results of the cobalt analyses of a number of commercially available iron products are given.

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Zusammenfassung Ein Verfahren zur spektrophotometrischen Bestimmung von Spuren Kobalt in reinem Eisen mit 2-Pyridyl-2-thienyl--ketoxim wurde angegeben. Dessen Empfindlichkeit wurde durch Verwendung von 4-cm-Küvetten erhöht. Das Beersche Gesetz gilt von 0,05 bis 0,600 ppm. Die Genauigkeit und Richtigkeit der Methode sowie der Einfluß verschiedener Ionen wurden dargelegt. Ergebnisse für eine Anzahl handelsüblicher Eisenprodukte wurden angeführt.

     

Catalytic olefination reaction of carbonyl compounds. A study on stereoselectivity of alkene formation

The mechanism of formation of alkene stereoisomers in the catalytic olefination reaction of carbonyl compounds was studied. 4-Chlorobenzaldehyde hydrazone 1 stereoselectively reacts with a number of F-, Cl-, Br-, and I-containing polyhaloalkanes in the presence of catalytic amounts of CuCl to give -substituted styrenes 2 with the more thermodynamically stable alkene isomer being the major product. A model for the formation of the stereoisomers of alkenes 2 in the olefination reaction is proposed. Stereoselectivity of the reaction is determined by elimination of copper(ii) halides from the lowest-lying conformers of organocopper intermediates II. According to quantum-chemical calculations, the elimination should involve the staggered conformations with antiperiplanar arrangement of C—Hal and C—Cu bonds and proceed by the E2 anti-elimination mechanism. The results of quantum-chemical calculations are in good agreement with the experimental E/Z alkene isomer ratios.     

Spectrophotometric determination of vanadium(IV) in the presence of vanadium(V) using Br-PADAP

In the present paper, a simple and sensitive method is proposed for vanadium(IV) determination in the presence of vanadium(V). This is based on the oxidation of vanadium(IV) present in the sample to vanadium(V) by addition of iron(III) cation, followed by a complexation reaction of iron(II) with the spectrophotometric reagent 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (Br-PADAP). The iron(II) reacts with Br-PADAP immediately, forming a stable complex with a large molar absorptivity. The vanadium(IV) determination is possible, with a calibration sensitivity of 0.549 g ml^–1, for an analytical curve of 18.8 ng ml^–1 to 2.40 g ml^–1, molar absorptivity of 2.80 × 10⁴ 1 mole^–1 cm^–1 and a detection limit of 5.5 ng ml^–1. Selectivity was increased with the use of EDTA as a masking agent. The proposed method was applied for the vanadium(IV) determination in the presence of several amounts of vanadium(V). The results revealed that 200 g of vanadium(V) do not interfere with determination of 5.00 g of vanadium(IV). The precision and the accuracy obtained were satisfactory (R. S. D.<2%).     

Extractive-spectrophotometric determination of tin as Sn(II)-ferron complex

Summary Tin(II) forms a yellow coloured complex with ferron which can be extracted into tribenzylamine-chloroform solution from dilute hydrochloric acid medium. Tin is determined spectrophotometrically by measuring the absorbance at 390 nm. Beer's law is valid up to 7 g Sn/ml with a sensitivity of 0.02 g Sn/cm². Chromium, manganese, iron, nickel, cobalt, copper, zinc, lead, magnesium, titanium, thorium, uranium and vanadium do not interfere. The method is quite simple and useful; its applicability has been tested by the analysis of synthetic samples and an alloy sample of gun metal.     

Komplexometrische Folgetitrationen von Eisen und Nickel sowie Kupfer und Nickel imμg-Bereich

Zusammenfassung Eine quantitative Bestimmungsmethode für Mikromengen Eisen und Nickel sowie Kupfer und Nickel, wie sie in Legierungen, Oxidgemischen und galvanischen Bädern vorkommen, wurde beschrieben. Die Metalle werden komplexometrisch mit ÄDTA und Kupferstandardlösung unter Verwendung einer kupferionensensitiven Elektrode und potentiometrischer Äquivalenzpunktindikation bestimmt. Eisen bzw. Kupfer werden direkt mit ÄDTA titriert, das Nickel dann in der gleichen Lösung durch Rücktitration des überschüssigen ÄDTA mit Kupferstandardlösung bestimmt.Die relativen Standardabweichungen der Bestimmungen liegen für Eisen bei ±(0,6 bis 1,2)%, für Kupfer bei ±(0,4 bis 0,8)% und für Nickel bei ±(0,6 bis 1,2)% jeweils für den Bereich von 800g bis 25g Metall. Unter den gewählten Bedingungen lassen sich mit dem Verfahren noch 25g Eisen, Kupfer bzw. Nickel bestimmen.

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Complexometric sequential titrations of iron and nickel as well as copper and nickel in theg range

Summary A quantitative assay method was described for microamounts of iron and nickel such as occur in alloys, oxide mixtures and galvanic baths. The metals were determined complexometrically with EDTA and standard copper solution using an electrode sensitive to copper ions and potentiometric indication of the equivalence point. Iron and copper were titrated directly with EDTA, and nickel then determined in the same solution by back-titration of the excess EDTA with standard copper solution.The relative standard deviations of the assays are ±(0.6–1.2)% for iron, at ±(0.4–0.8)% for copper, and at ±(0.6–12.2)% for nickel for the range from 800–25g metal respectively. Under the conditions chosen, 25g of iron, copper or nickel can be determined using the procedure.

     

Chromatographic separation of uranium

Summary A solvent mixture of methanol and saturated ammonium acetate solution (18:2) is employed for the separation of uranium in ppm quantities from iron (up to 1000 fold excess) by paper chromatography. The separation from both iron and copper can be achieved by using a solvent mixture of methyl ethyl ketone, acetic acid, and diluted nitric acid (1613).

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Zusammenfassung Zur papierchromatographischen Trennung von ppm-Mengen Uran von Eisen (in bis zu 1000 fächem Überschuß) wird ein Laufmittel aus Methanol und gesätt. Ammoniumacetatläsung (182) benutzt. Die Trennung von Eisen und Kupfer wird mit einem Gemisch aus Methyläthylketon, Essigsäure und verd. Salpetersäure (1613) durchgeführt.

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The author is highly thankful to Prof. Bh. S.V. Raghava Rao for his valuable suggestions and guidance throughout the progress of this work.Thanks are also due to the Department of Geology, Andhra University for supplying the samples and to the Counsil of Scientific and Industrial Research, New Delhi for the award of a fellowship.     

Zur Kenntnis organischerLewis-Säuren, 36.Cis—trans-Gleichgewichte und Konformationen von 2,(x)-Dialkyl-1-dicyanomethylencyclohexanen. Wahlweise einfache Darstellung dercis- odertrans-Formen

Knoevenagel condensation of malononitrile withcis- andtrans-2,5-dimethylcyclohexanone (1 c and1 t, respectively) leads to2 c and2 t, respectively, and withtrans-1-decalone to4 t. The equilibria2 c2 t and4 c4 t have been determined as well as, by means of 270-MHz-¹H-NMR, the conformations of these four compounds. The dicyanomethylene group is found to induce axial positions of neighbouring alkyl residues on the cyclohexane ring (or when this is impossible, as in the case of4 t, the twist form of the cyclohexane ring). This results in a strong predominance of thecis isomers in the equilibria2 c2 t and4 c4 t whereas thetrans isomers strongly predominate in the equilibria among the starting ketones. This situation allows the optional preparation of2 c or2 t, and of4 c or4 t, from the more stable starting ketone (or ketone mixture). The free conformational energy of the distorted twist form of4 t amounts to 17 kJ/mol.

Herrn Prof. Dr.E. Ziegler, Graz, zum 70. Geburtstag in aufrichtiger Verbundenheit gewidmet.