Transition metal nitrosyls as nitrosylation agents : II.Photo-nitrosylation of η5-C5H5V(CO)3L(L = CO,Pz3) by [Co(NO)2Br]2

η⁵-C₅H₅V(NO)₂CO is prepared in 40% yield by the photo-reaction between η⁵-C₅H₅V(CO)₄ and [Co(NO)₂Br]₂.η⁵-C₅H₅V(NO)₂CO reacts by an S_N1 mechanism with various phosphines PZ₃ to yield η⁵-C₅-H₅V(NO)₂PZ₃. The phosphine complexes are also obtained by photo-induced ligand interchange between η⁵-C₅H₅V(CO)₃PZ₃ and [Co(NO)₂Br]₂, or η⁵-C₅H₅V(CO)₄ and Co(NO)₂Br(PZ₃). In all cases, the main cobalt species formed is Co(NO)(CO)₃. While the one-bond vanadiumphosphorus coupling constants of most of the phosphine complexes are virtually the same (ca 410 Hz),the chemical shift values δ(⁵¹V) (?1328 to ?973 ppm rel. VOCl₃) decrease in the order PF₃ > CO > P(OR)₃ > P(alkyl)₃ > PPh₃ > PPh(NEt₂)₂, reflecting the decreasing π-acceptor ability of the ligands. δ(⁵¹V) also decreases in the series of alkylphosphines PR₃ (R = Me, Et, Prⁿ, Buⁱ, Prⁱ, BU^t) as the cone angle of PR₃increases.     

Chronocoulometric study of the electrochemistry of Prussian blue

During the electrochemical oxidation of Prussian blue (PB) to Prussian yellow (PY), an electrocatalytic oxygen production proceeds at the electrode when aqueous electrolyte solutions are used. The formed oxygen is scavenged by the PY, probably by absorption, and it is consumed during the electrochemical reduction of PY to PB by a heterogeneous chemical reaction of PB with oxygen to PY and hydrogen peroxide. Because of this catalytic regeneration of PY, it is impossible to determine the amount of low-spin iron by chronocoulometry using a potential program in which PB is first oxidized to PY and then the charge is measured to reduce PY to PB. The latter charge is biased by the electrocatalytic PY regeneration.     

Verhalten von ng- und μg-Mengen biochemisch interessierender Amine bei Trennverfahren,wie Ionenaustausch-Chromatographie,Mitfällung und Extraktion

The behaviour of ng- and μg-amounts of amines of biochemical interest is compared. ng-amounts are co-precipitated from aqueous solutions with the tetraphenyloborates of potassium, ammonium and creatinine. A separation from potassium chloride, ammonium chloride and creatinine is achieved by extraction of the amines with methanol. The elution volumes of about 50 amines during ion-exchange chromatography using a weakly acidic resin are compared. A procedure has been elaborated by which the amines can be collected from urine.     

Sulfide ion electrooxidation catalysed by cobalt phthalocyanine microcrystals

Electrooxidation of sulfide ion catalysed by microcrystals of cobalt phthalocyanine was investigated by cyclic voltammetry in 0.5M KNO₃ at pH 9.22. Traces of catalyst were immobilized at the surface of a paraffin-impregnated graphite electrode by the mechanical transfer of its powder. The electro-oxidation of HS^– proceeds in two irreversible steps, with the first peak between 0 V and –0.12 V and the second at 0.17 V. The first step is second order in HS^– and its product is the adsorbed disulfide, which may further dissociate to give adsorbed sulfur atoms. The reduction of sulfur occurs at –0.1 V.     

Vacancy ion-exclusion chromatography of carboxylic acids on a weakly acidic cation-exchange resin

In this preliminary study, a new approach to ion-exclusion chromatography is proposed to overcome the relatively poor conductivity detection response which occurs in ion-exclusion chromatography when acids are added to the eluent in order to improve peak shape. This approach, termed vacancy ion-exclusion chromatography, requires the sample to be used as eluent and a sample of water to be injected onto a weakly acidic cation-exchange column (TSKgel OApak-A). Vacancy peaks for each of the analytes appear at the retention times of these analytes. Highly sensitive conductivity detection is possible and sharp, well-shaped peaks are produced, leading to efficient separations. Retention times were found to be affected by the concentration of the analytes in the eluent, and also by the presence of an organic modifier such as methanol in the eluent. Detection limits for oxalic, formic, acetic, propionic, butyric and valeric acids were 0.1, 0.2, 0.3, 0.3, 0.4 and 0.5 microM, respectively, and linear ranges for some acids extended over two orders of magnitude. Precision values for retention times were 0.21% and for peak areas were <1.90%. The vacancy ion-exclusion chromatography method was found to give detection responses four to 10 times higher than conventional ion-exclusion chromatography using sulfuric acid eluent and two to five times higher than conventional ion-exclusion chromatography using benzoic acid eluent.     

Analytical investigation of the properties and uses of a new hydrophobic molecular sieve

Distribution coefficients and capacities have been determined for many different organic compounds on a new molecular sieve called silicalite, which does not adsorb water but does adsorb small organic molecules with diameters up to 6 A, from both liquid and gaseous streams. The characteristics of silicalite have been examined closely and new applications for it are briefly described.     

Zur Synthese von 3-Desoxy-aldulosonsäuren

The condensation of 2.4-ethylidene-erythrose with the sodium salt of diethyl-phosphono-piperidino-ethylacetate yields an enamino-lacton V which is converted under mild conditions into an α-keto ester, 2-oxo-3-desoxy-gluconic acid, and its quinoxaline derivative.     

Coulometric titration of acids in non-aqueous solvents

Coulometric titrations of mineral acids, sulphonic acids, carboxylic acids, enols, imides and phenols have been carried out in t-butanol or in acetone with electrically generated tetrabutylammonium hydroxide. Either a potentiometric titration or a visual indicator end-point may be used. The amount of acid titrated ranges from 10 to 60 muequiv, and the precision and accuracy of the method are excellent.     

Application of the photoionization detector for the determination of ethanol in aqueous solutions and human breath

A determination of ethanol is described, which is based on a purging system in conjunction with a photoionization detector. With that system a fast and reliable determination of ethanol in aqueous solutions is possible. The system has been used for the analysis of wine. The 3delta-detection limit has been 0.005% ethanol, the relative standard deviation 4.8 to 6.0% and the time constant of the entire analytical system 20 s. The photoionization detector has been also applied to the analysis of artificial and genuine human breath. A comparison with gas-chromatography and non-dispersive IR-detection has been proven the reliability of results.