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101.
We have demonstrated that a bipyrimidinylplatinum-polyoxometalate, [Pt(Mebipym)Cl2]+[H4PV2Mo10O40]-, supported on silica is an active catalyst for the aerobic oxidation of methane to methanol in water under mild reaction conditions. Further oxidation of methanol yields acetaldehyde. The presence of the polyoxometalate is presumed to allow the facile oxidation of a Pt(II) intermediate to a Pt(IV) intermediate and to aid in the addition of methane to the Pt catalytic center. 相似文献
102.
A phenanthroline ligand has been covalently modified at the 2 and 9 positions by an aminophenylhexamolybdate substituent. The 1H NMR spectrum indicated a strong electron-withdrawing effect of the hexamolybdate (Mo6O19(2-)) moiety on the phenanthroline ligand. UV-vis and cyclic voltammetry showed extended conjugation of the hybrid phenanthroline-polyoxometalate compound and the possibility of easy oxidation of the extended phenanathroline ligand. Further EPR experiments provided strong evidence for an intramolecular charge-transfer process with the formation of a phenanthroline cation radical and a reduced hexamolybdate. 相似文献
103.
Helmut Simon Johann Bader Helmut Günther Stefan Neumann Jordanes Thanos 《Angewandte Chemie (International ed. in English)》1985,24(7):539-553
It has been known for many decades that chiral compounds can be obtained by stereospecific biocatalytic reduction. Further significant methodological developments in this field have, however, only been made during the past ten years; they include the application of previously unused microorganisms and electron donors, the discovery of additional substrates for the known reductases, the development of methods for regenerating reduced pyridine nucleotides, and the discovery of new reductases which were sought for specific preparative purposes. Many chiral compounds can now be synthesized by microbial hydrogenation using H2 and hydrogenase-containing microorganisms as well as by electromicrobial or electroenzymatic reduction. In the two latter methods, anaerobic or aerobic organisms are supplied with electrons from electrochemically reduced, artificial mediators, e.g., methyl viologen. Reductases that do not require pyridine nucleotides and can accept electrons directly from reduced viologens are especially useful. Two examples of this type of enzyme are described which are of preparative interest. Many cells contain methyl viologen-dependent NAD(P) reductases, a large number of which have still not been characterized. A productivity number is proposed which allows different methods of bioconversion with microorganisms to be compared. The productivity numbers of compounds synthesized by the methods described in this review are often 10- to 100-fold higher than those of substances obtained by conventional techniques. 相似文献
104.
105.
The configurational isomers of astaxanthin (3,3′-dihydroxy-β,β-carotene-4,4′-dione) from the flesh of salmon (Salmo salar and Oncorhynchus) caught at different places in Europe and Canada were isolated and analyzed as (?)-camphanic acid diesters by means of HPLC. The biological variation in the composition of the configurational isomers in seven fish was surprisingly similar: 78 to 85% of (3S, 3′S)-astaxanthin, 12 to 17% (3R, 3′R)-astaxanthin and 2 to 6% meso-astaxanthin. 相似文献
106.
The application of solid layer crystallization techniques in industry is arousing ever more interest. One reason is the increasing demand for ultrapure products, and another is the energysaving potential of this separation technology.This article examines solid layer melt crystallization as concerns its purification efficiency. The crystallization process was carried out in two different modes, whereby the process parameters were varied and post-crystallization treatments were additionally applied. The experimental results were used as the basis for a mathematical fit of a semi-empirical expression which predicts the purification efficiency. It was used for a design of different multistage plants, which operate with different crystallization strategies. One result is that a comparable product quality is attainable with a simple process technique in combination with post-crystallization treatments, instead of a more complicated and therefore more expensive process technique.The authors wish to acknowledge support by the EU (JOULE program), which helped attainment of some results presented here. 相似文献
107.
Monika Schuster Robert Inführ Claudia Turecek Jürgen Stampfl Franz Varga Robert Liska 《Monatshefte für Chemie / Chemical Monthly》2006,137(7):843-853
Summary. To substitute cross-linked photopolymers in rapid prototyping of mold materials and therefore extend the range of materials
which can be casted, organo-soluble photopolymers were developed. Branched bisalkylacrylamides were suitable as base component
for such formulations, due to their high reactivity, good mechanical properties, and excellent solubility of the formed polymers.
These molding materials were used to prepare cellular biocompatible materials which could be used as bone replacement materials.
Biocompatible crosslinkers based on methacrylates from hydrolyzed gelatine or lactic acid ethyleneglycol blockcopolymers and
commercially available reactive diluents are the base components of such a formulation. Biocompatibility was investigated
by osteoblast-like cells. Cellular biocompatible parts were obtained by thermal polymerization in soluble mould materials
prepared by 3D-photoshaping. 相似文献
108.
Zusammenfassung Die früher beschriebene Apparatur zur Bestimmung der primären Aminogruppe wurde verbessert. Auch die Handhabung wurde vereinfacht. Die einzelnen Teile der Apparatur (Desaminierungsteil, Absorber) können nun unabhängig voneinander ausgewaschen und luftfrei gemacht werden. Die Absorber sind für etwa 30 bis 50 Analysen benützbar, bevor sie erneuert werden müssen.
Der Firma P. Haack, Wien danken wir für das besondere Entgegen-Kommen bei der Entwicklung der Apparatur. 相似文献
Summary The apparatus previously described for the determination of primary amino groups has been improved. Also the manipulation is simplified. The individual segments of the apparatus (deamination part, absorber) can now be washed out independently of each other, and rendered free of air. The absorbers may be used for around 30 to 50 analyses before they must be renewed.
Der Firma P. Haack, Wien danken wir für das besondere Entgegen-Kommen bei der Entwicklung der Apparatur. 相似文献
109.
Heinz Falk Franz Lehner Marianne Rothböck 《Monatshefte für Chemie / Chemical Monthly》1985,116(11):1359-1361
Donors are added regioselectively to position 10 of 2,3-dihydrobilatrienes-abc in a reversible reaction, which is complicated in case of strongly basic donors due to the easy deprotonation of the partially saturated ring. Compared to the bilatrienes-abc the addition equilibrium is retarded by about two orders of magnitude. 相似文献
110.
Gerald Kainz und Franz Scheidl 《Fresenius' Journal of Analytical Chemistry》1964,202(4):251-258
Zusammenfassung In der vorliegenden Arbeit wurde untersucht, wie man die vergaste Probe am besten durch die Verbrennungszone führt, damit man eine vollständige Vermischung mit Sauerstoff erhält; denn bei hohen Temperaturen ist nicht so sehr die Umsatzgeschwindigkeit der Probe mit Sauerstoff bestimmend, sondern die Mischungsgeschwindigkeit mit Sauerstoff. Es wurden zwei Möglichkeiten untersucht. Bei der schnellen Vergasung im geraden Rohr ergab sich, daß sich dabei ein Substanzpfropf bildet, der durch Sauerstoff (im Wege der Diffusion) durchdrungen werden muß. Eine quantitative Oxydation ist nur dann möglich, wenn die Einwaage auf den Durchmesser des Verbrennungsrohres abgestimmt ist. Bei Mikroeinwaagen (3 mg) muß der Durchmesser des Verbrennungsrohres mindestens 20 mm betragen.Eine wesentlich intensivere Vermischung der Substanzdämpfe mit Sauerstoff wird bei der Verbrennung in der Flamme erreicht, die auf Wickbold bzw. Radmacher zurückgeht. Hierbei wird die Probe in einem engen Rohr unter Durchleiten von Sauerstoff oder Stickstoff vergast und durch eine enge Düse in die heiße Verbrennungszone eingeblasen. An der Düse bildet sich eine Flamme, in die Sauerstoff intensiv eindiffundiert. Eine einfache Apparatur, die eine schnelle, bei Mikroeinwaagen von der Geschicklichkeit des Analytikers unabhängige Vergasung und Verbrennung zuläßt, wird beschrieben.
Summary In this paper the problem is investigated how to pass the vaporised sample through the combustion zone in order to attain a complete mixture with oxygen; at high temperatures the completeness of combustion depends not so much on the rate of reaction with oxygen than on the rate of mixing with oxygen. Two experimental procedures have been investigated. High speed vaporisation in straight tubes leads to a plugshaped concentration of the sample, which must be penetrated by oxygen (diffusion). Using this procedure, a quantitative oxidation is only possible, if the sample weight is in a proper relation to the diameter of the tube. In microanalysis (3 mg of sample) the diameter of the combustion tube must be 20 mm or more.A much more intensive mixing of the vaporised sample with oxygen is attained by the combustion in the flame proposed by Wickbold and Radmacher. The vaporised sample is blown out of a small tube through a narrow nozzle into the heated combustion zone. On the nozzle a flame is formed, in which oxygen is diffusing intensively. A simple apparatus is described, which permits a rapid vaporisation and quantitative oxidation. Analysing micro samples the vaporisation was found to be independent of the skill of the analyst.相似文献