Synthesis and structure of 6- and 7-(acylmethyl)pteridines

6-(Acylmethyl)-7-hydroxypteridines 7-14 as well as the isomeric 7-(acylmethyl)-6-hydroxypteridines 15-22 were prepared by condensation of 5,6-diaminouracils 1 and 2 with ethyl aroylpyruvates 3-6 in pyridine and hydrochloric acid, respectively. The structures of the newly synthesized compounds were confirmed by their hydrolysis into the 7-hydroxy-6-methyl- 23 , 24 and 6-hydroxy-7-methylpteridines 25 and 26 . The synthesis of the 2-(methylthio) derivative 28 is also described.     

Reactivity of 3-amino-, 3-halogeno-, and 3-nitro-2-pyrones and thiopyrones

Substituted pyrrole and furan-2-carboxylic acids were obtained from 3-amino- and 3-halogeno-2-pyrones. The reactions of several substituted 2-pyrones and thiopyrones with different amines and carbonyl reagents were studied.     

The electrochemical behavior and characterization of the anodic oxide film formed on titanium in NaOH solutions

Titanium dissolution and passivation were studied in NaOH aqueous solution using open-circuit potential, potentiodynamic and potentiostatic techniques. Potentiodynamic data showed that the active-passive transition involves active metal dissolution followed by formation of a poorly conducting passive oxide film that passivates the electrode. The critical current density varied with pH as d log<I> j</I><SUB>m</SUB>/d pH=-0.098 in the pH range 11.00–14.00, while the passivation potential is changed according to the following two features: at pH 10.55–13.00, d<I>E</I><SUB>m</SUB>/d pH=-0.06 V; and at pH 13.50–14.00, d<I>E</I><SUB>m</SUB>/d pH=-0.40 V. The apparent activation energy, E*, was calculated from the slope of the Arrhenius plot and was found to be 12.6 kJ mol^–1. Current-time transients showed that the growth of titanium oxide passive film is a diffusion-controlled process. XPS measurements indicated that the passive oxide film consists mainly of TiO₂ and a mixture of suboxides of Ti₂O₃ and TiO. Electronic Publication     

1,1′‐Di­acetyl‐3‐hydroxy‐2,2′,3,3′‐tetra­hydro‐3,3′‐bi(1H‐indole)‐2,2′‐dione

In the title compound, C₂₀H₁₆N₂O₅, both of the 1‐acetyl­isatin (1‐acetyl‐1H‐indole‐2,3‐dione) moieties are planar and form a dihedral angle of 74.1 (1)°. Weak intermolecular hydrogen bonds and C—H?π interactions stabilize the packing in the crystal.     

Die Bestimmung des Eisens in Pferdeserum

Zusammenfassung Daß die Bestandteile des Serums die Genauigkeit der Bestimmung des Eisens nicht im mindesten beeinflussen, wird durch die Tatsache bewiesen, daß die Richtungskoeffizienten der Gleichungen für die Bestimmungen in Wasser und in Serum völlig identisch sind. Die beschriebene Methode der Bestimmung des Eisens in Pferdeserum hat sich als zuverlässig erwiesen. Die Fehler der Bestimmung sind minimal. Das Eisen wird mit Trichloressigsäure bei 90 bis 95° C extrahiert. Dem Serum zugegebenes Eisen(III) wurde quantitativ wieder gefunden.

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Summary The fact that the directional coefficients of the equations for the determinations in water and in serum are completely identical proves that the constituents of the serum do not affect the accuracy of the determination of the iron in the slightest.The method described for determining iron in horse serum has been found to be reliable. The errors of the determination are minimal. The iron is extracted with trichloroacetic acid at 90–95° C. Iron(III) added to the serum was recovered quantitatively.

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Rèsumè Il a été possible d'établir que les constituants du sérum n'ont aucune influence sur la précision du dosage du fer. Cette assertion résulte du fait que les coefficients de pente des équations utilisées pour le dosage du fer sont absolument identiques pour l'eau et pour le sérum. La méthode décrite pour le dosage du fer dans le sérum de cheval peut être appliquée avec sûreté. L'erreur de la détermination est très faible. Le fer est extrait par l'acide trichloracétique à une température comprise entre 90 et 95° C. Le fer(III) préalablement introduit dans le sérum, y a été retrouvé quantitativement.

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An dieser Stelle möchten wir auch Herrn Dr.M. Bajzer vom Zentralen hygienischen Institut in Zagreb für die statistische Bearbeitung unsere Resultate danken.     

A simple and selective flow-injection spectrophotometric determination of copper(II) by using acetylsalicylhydroxamic acid

A new simple, and rapid flow-injection spectrophotometric method is developed for the determination of trace amounts of Cu(II) by using a new chromogenic reagent acetylsalicylhydroxamic acid (AcSHA). The method is based on the formation of colored Cu(II)-(AcSHA)₂ complex. The optimum conditions for the chromogenic reaction of Cu(II) with AcSHA is studied and the colored (green) complex is selectively monitored at λ_max 700 nm. With the reagent carrier solvent (dimethylsulfoxide (DMSO) and acetate buffer, pH 4.2) flow-rate of 1 ml min⁻¹, a detection limit (2S) of 1 μg l⁻¹ Cu(II) was obtained at a sampling rate of 80 sample h⁻¹. The calibration graph was linear in the Cu(II) concentration range 5-120 μg l⁻¹. The relative standard deviation (n=10) was 0.64% for a sample containing 60 μg l⁻¹ Cu(II). The detailed study of various interferences confirmed the high selectivity of the developed method. The method was successfully applied to determine trace amounts of copper(II) in river and seawater samples. The accuracy of the method was demonstrated by the analysis of standard reference materials C12X3500 and C14XHS 50.     

Cathodic adsorptive stripping voltammetric determination of nalidixic acid in pharmaceuticals, human urine and serum

The quinolone antibacterial agent nalidixic acid (NAL) was studied by cyclic voltammetry (CV) and cathodic adsorptive stripping voltammetry (CASV). A sensitive method is described for the determination of NAL in its pure form, dosage forms and biological fluids. Controlled adsorptive accumulation of NAL on a hanging mercury drop electrode provides the basis for the direct stripping measurement of that compound in the nanomolar concentration level. Different variables were studied and optimized. The proposed method depends upon the voltammetric activity of NAL in Britton-Robinson buffer, whereby a well-defined cathodic peak is produced at pH 5.0 in presence of NO(3)(-). The calibration graph to determine NAL was linear in the range 7.4x10(-8)-2.5x10(-5) M by CASV. CAS voltammetry has been proved to be advantageous over a liquid chromatographic (LC) technique, allowing to detection limit signal to noise ratio, (s/n=3) of 0.766 ng ml(-1) (3.3x10(-9) M) NAL to be reached. The relative standard deviation (n=5) was 5.2% at concentration level of 1.0x10(-7) M NAL. The degree of interference from coexisting metal ions on the CASV signal for NAL was evaluated. The method was applied to two different commercial pharmaceutical products (Negram tablets and suspension) with very good recoveries. It was also shown that the method was successfully applied to the determination of NAL in human urine and blood serum. Mean recoveries were 98.8+/-0.3 and 98.9+/-0.41%, respectively.     

The Stabilities of the o-Carboxyphenylhydrazo-Ethylacetoacetate OF Cu,Ni, Co,Zn, Mn and Cd Chelate Compounds in Different Solvents

The dissociation constants for o-carboxyphenylhydrazoethylacetoacetate (o-CPHEA) ligand, as well as the stability constants for the divalent metal complexes of Cu, (II), Ni (II), Co (II), Zn (II)and Cd (II) ions, have been calculated pH-meterically in different solvents. The dissociation constans pK₁=4.10 and pK₂=10.55 of the insoluble organic ligand are calculated in aqueous medium. The effect of solvents, the relation between stabilities and both electronegativities and ionization potential are studied.     

Electron transfer at tetrahedral cobalt(II). Part 1. Kinetics of bromate ion reduction

Summary The bromate ion reduction by 12-tungstocobaltate(II) anion has been investigated. The reaction obeys the empirical rate law:-d[reductant]/dt=5(a+b[H⁺]²)[BrO ₃ ^– ][reductant]: where a=(2.49±0.18)×10^–4M^–1 s^–1, b=(4.65±0.20)×10^–5M^–3s^–1 at 24.5±0.1°C [H⁺]=0.05–1.50M and I=2.0M (NaClO₄). This rate law is interpreted in terms of parallel reactions of BrO ₃ ^– and H₂BrO ₃ ⁺ . On the basis of the observed anion catalysis, substitution intertness of the reductant and Marcus type linear free energy relations, the outer sphere mechanism is proposed for both pathways.