In memoriamMichell J. Sienko

Calcium urate hexahydrate, Ca(C₅H₃O₃N₄)₂ · 6H₂O, has been synthesized for the first time. A tentative assignment of some infrared and Raman bands is given by referring to the isotopic frequency shifts, group frequency considerations, Raman intensities as well as to the spectrum of potassium salt. The spectroscopic data suggest that there are, at least, two types of water molecules in the unit cell. Centrosymmetric unit cell is proposed to explain the spectral features of this compound. X-Ray powder diffraction data are also given.     

Bewertung von glättungsexperimentenEvaluation of curve-smoothing techniques

Conditions for curve smoothing can be compared experimentally by simulation or theoretically by applying information theory. Simulation experiments provide the conditions either for optimization of the signal/noise ratio or for minimizing the systematic error; the results presented are easily evaluated in practice. Information theory assumes that loss of information will not be caused by the smoothing procedure. Conditions for maximal noise improvement for a preset systematic error are then obtainable; the regularities are easily interpreted from graphs.     

Preliminary communicationA remarkable intramolecular difference in local scrambling rates for two Mo(CO)3 groups and absence of metal-to-metal scrambling

The carbon-13 NMR spectrum of guaiazulenedimolybdenum hexacarbonyl has been examined from ?112 to +92°C. There is local scrambling of the three CO's on each Mo atom but at vastly disparate rates; resonances for one set coalesce below ?112°, those of the other at about ?30°C. No scrambling of CO's from one metal atom to the other is observed.     

A new alkylamidation reactionRegiospecific condensation of carbanions on cyclo 1,3- oxoimminium salts

Cyclo 1,3-oximminium salts are found to react regiospecifically with functional carbanions. Steric effects induced at the C-2 site on salts or at the carbanionioc centers promote the condensation at the C-5 or C-6 opposite sites. A bulky substituent such as 2-mesityl group is a powerful auxiliary which not only modifies the steric environment at the reactive C-2 site but also contributes to enhance the reactivity of the cyclo oxoimminium ring.     

Effizienz der regression in der röntgenspektrometrieThe efficiency of regression calculations in x-ray spectrometry

(The efficiency of regression calculations in x-ray spectrometry)Regression fitting by the least-squares technique minimizes analytical errors. Examples in the literature indicate the possible errors of the method with regard to overfitting, extrapolation and gaps in the concentration range of the standard samples. Strict consideration shows that in practice such errors are insignificant. The problem of unnecessary parameters is discussed; it is shown that regression fitting can cope with such parameters without increased error. The method can also provide a criterion for the necessity of parameters in calibration functions. The most important sources of error in x-ray spectrometry, which are enumerated, do not include the regression calculations.     

Bestimmung und abtrennung von sauerstoffverunreinigungen in reinst-selenThe determination and separation of oxygen impurities in high-purity selenium

(The determination and separation of oxygen impurities in high-purity selenium)By distillation in high vacuum, high-purity selenium is almost completely freed from impurities caused by metallic elements, oxides and water. If bulk vitreous selenium has a suitable thermal history, the oxygen content may be determined from the intensity of the oxide absorption band at 932 cm^?1 in the i.r. spectrum of the glass. In distilled selenium this content is < 1 × 10^?4 wt.< %.     

Microcalorimetre pour l'etude des reactions en chimie du fluorMicrocalorimeter for the study of reactions in fluorine chemistry

A miniaturized differential calorimeter (Type M.C.B.)\b7 specially fitted for fluorine chemistry is described. It includes two identical cells connected through a chromel/constantan thermo-électric element; these two cells are equiped each with a fixed value calibrating resistance and a thermocouple. The sensitivity of the aparatus is 70μv/mW with a time lag of 30 To 35 secondes the usable temperature range with lies between - 200 To + 650°C depends on the character of the reactant. The temperature variation of system can be programmed up to 3°C/mn. The apparatus has been concerned in two distinct parts, on works in high vacuum and recieves the reactants, the other works in a protected atmosphere or vacuum. This microcalorimeter has been used for measurement of heats of adsorption, of complexation and of decomposition: of heats of solid/solid and solid/liquid transitions, of heats of dissolution and of mixing, and also for the determination of spécific heats of fluorinated and other compounds.     

Reaktionskalorimeter und reaktionsrohrbehälter mit verbessertem wärmedurchgangskoeffizientenReaction calorimeter and agitated reaction vessel with improved overall heat transfer coefficient

In present types of reaction calorimeters and agitated reaction vessels the overall heat transfer coefficient between reaction mixture and cooling fluid is low, caused by the low heat transfer coefficient on the cooling fluid side. Consequently the thermal response time is high and a quasi-isothermal reaction is difficult to obtain. A new construction of a cylindrical double wall reaction vessel is presented which yields a higher overall heat transfer coefficient than conventional constructions. The cooling fluid flows through a helically shaped flow path between the walls. The outer wall is especially bulged to improve strength and heat transfer. Two reaction vessels are tested yielding good results.     

Komplexbildung und extraktion von zinn mit potentiel dreizähnigen dianionischen ligandenComplex formation and liquid-liquid extraction of tin with potentially tridentate dianionic ligands

Pulse polarography was used to study the extraction of tin(IV) from chloride solution with potentially tridentate dianionic ligands under unbuffered conditions. The ligands usually contained enolizable groups or were produced by splitting heterocyclic rings. The most favourable extractant was 2-(2′-hydroxyphenyl)-quinolin-8-ol, which extracted tin in the pH region 2–8; all othe rligands gave good extraction only at pH 6–8. In the organic phase, 1:1 chelates are formed in all cases. The composition of the complexes was also proved by the isolation of the solid compounds. These complexes were characterized by their Mössbauer parameters.     

Preliminary communicationCatalytic olefin hydrogenation with nonacarbonyltris(triphenylphosphine)triruthenium and its derivatives. Crystal structure of [Ru2(CO)5(PPh3)(μ-PPh2)(μ-OCPh)]

The complexes [Ru₃(CO)₇(PPh₂)₂(C₆H₄)] and [Ru₂(CO)₅(PPh₃)(μ-PPh₂)(μ-OCPh)] were obtained by pyrolysis of [Ru₃(CO)₉(PPh₃)₃] and tested as catalysts for the hydrogenation of cyclohexene and 2-cyclohexen-1-one. The structure of [Ru₂(CO)₅(PPh₃)(μ-PPh₂)(μ-OCPh)] was established by a single crystal X-ray diffraction study.     

Entwicklung einer flieβinjectionsmethode zur bestimmung von chlorid im spurenbereich durch leitfähighkeitsdiffernzenA flow-injection method for the determination of trace amounts of chloride

The indirect determination of chloride in water is based on measurement of the difference in conductivity after the sample has passed through ion-exchange columns in the hydrogen form and silver form. The linear response range is about 0.5–10 μg g^?1 chloride (with 3 μg g^?1 nitrate and 5 μg g^?1 sulfate); the detection limit is about 50 ng g^?1 chloride but depends strongly on the concentrations of other anions.     

Nucleophilic substitutions of α-halo-ketones-XXIIAcetolysis of α' - phenoxy - α - chloro - ketones. A comparison of their reactivity with that of the corresponding thioethers

The results obtained in the acetolysis of α - chloro - ketones 1a-e are compared with those previously reported for the acetolysis of the corresponding α' - phenylthio-α - chloro - ketones 15a-e and discussed in terms of the enolization-solvolysis mechanisms (Schemes 1 and 2).     

Stereoselective additions to carboxylic acid dianions and β-lactone substituted ester enolatesApplication to the synthesis of racemic epi-blastmycinone, δ-multistriatine,paraconic esters and lignantype dilactones

New stereoselective syntheses are reported for racemic 4-epi-blastmycinone (6) and δ-multistriatine (13) utilizing the anti-configurated γ, β-unsaturated β-hydroxy-carboxylic acids 2a/b. A diastereo- and enantioselective aldoltype addition of phenylacetic acid dianion to benzaldehyde has been achieved by employing optically active alkoxide amide bases. Finally, highly stereocontrolled additions to the novel β-lactone substituted ester enolates 22 are described.     

Coumarin-6-sulphonyl chloride: a novel label in fluorimetry and phosphorimetry Part 1. Synthesis and Luminescence PropertiesagauS.M.Z. Al-Kind1

Coumarin-6-sulphonyl chloride was synthesized from coumarin in a single step and characterized. It was used to label amines, amino acids and phenols in mild conditions. The products of such reactions show intense fluorescence in alkaline solutions as a result of a photolytic ring-opening reaction. The derivatives are also phosphorescence at 77 K without ring opening.     

Komplexbildung und extraktion von kupfer und eisen sowie gallium mit isomeren langkettigen alkylchinolin-8-olenComplex formation and liquid-liquid extraction of copper,iron and gallium with isomeric long-chain alkylquinolin-8-ols

The extraction of copper(II) and iron(III) with the 5-nonyl-, 5- and 7-decyl- and 5-chloro-7-decyl derivatives of quinolin-8-ol was studied with chloroform, benzene or toluene as the organic solvent. Isomeric extractants show only small differences and are very suitable for the extraction of copper and its separation from iron, similarly to Kelex 100 (7-dodecenylquinolin-8-ol). With these derivatives log K_ex values are ?5.18 to ?6.08 for iron(III) with pH_0,5 = 4.5 to 5, whereas log K_ex values are 1.54 to 1.82 for copper(II) with pH_0,5 ≈ 1.35. The chelates of copper, iron and gallium with isomeric ligands, isolated as the solids, have characteristic differences in melting points and solubilities. To extract gallium from alkalin solution, only 7-alkyl-8-quinolinols proved as favourable.     

Dosage de la silice des silicates,apres distillation,par gravimetrie du molybdosilicate de quinoleineThe determination of silica in silicates by distillation and gravimetry as quinoline 12-molybdosilicate

The determination of silica in silicates by distillation and gravimetry as quinoline 12-molybdosilicateQuantitative distillation of silica as hexafluorosilicic acid is followed by gravimetric determination of the silicate as quinoline 12-molybdosilicate. Precise results are obtained even when the samples contain phosphorus and fluorine. Compared to classical insolubilization procedures with strong acids, the proposed method is quicker and more sensitive, being applicable down to ca. 1 mg SiO₂. Its application is limited to silicates decomposed by hot sulphuric acid—hydrofluoric acid mixtures. The accuracy of the procedure is confirmed by the results for numerous reference standards.     

Synthese de composes aromatiques comportant les groupements ocf2br et scf2brI - Action du dibromodifluoronéthane sur les thiophénate et phénate de potassium

The synthesis of, C₆H₅OCF42Br and C₆H₅SCF₂Br from CF₂Br₂ is discribed.