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131.
Summary A rapid sensitive method for the determination of microgram amounts of sulphur is described. Sulphur (free or combined) in organic substances is oxidised completely in an oxygen atmosphere over a platinum gauze catalyst after a preliminary incomplete combustion in air. The oxides of sulphur are collected on silver gauze at 550°. The oxygen is purged from the apparatus with a stream of nitrogen and then the silver sulphate is heated in a stream of hydrogen to yield hydrogen sulphide which is collected in an alkaline zinc acetate solution and subsequently determined spectrophotometrically by the methylene blue method.The recovery of sulphur in the range 5–40g was 100±5%. The method takes less than 25 minutes for a single determination and is reliable for the determination of as little as1
g of sulphur in all types of organic compounds. Solid, liquid, or gaseous samples may be used.
Zusammenfassung Eine schnelle, empfindliche Methode zur Bestimmung von Mikrogrammmengen Schwefel wurde beschrieben. Freier oder gebundener Schwefel in organischem Material wird nach unvollständiger Verbrennung in Luft in Sauerstoffatmosphäre über einem Platindrahtnetz vollständig oxydiert. Die Schwefeloxide werden auf Silberdrahtnetz bei 550° gebunden. Der Sauerstoff wird mit Stickstoff aus der Apparatur gespült und dann das Silbersulfat im Wasserstoffstrom zu Schwefelwasserstoff reduziert, der in alkalischem Zinkacetat aufgefangen und dann nach der Methylenblaumethode spektrophotometrisch bestimmt wird.In der Größenordnung zwischen 5 und 10g wird der Schwefel zu 100±5% erfaßt. Eine Einzelbestimmung dauert weniger als 25 Minuten. Für alle Arten organischer Verbindungen, ob fest, flüssig oder gasförmig, eignet sich das Verfahren für die Bestimmung von 1g Schwefel und darüber.
Résumé On décrit une méthode rapide et sensible pour le dosage de quantités de soufre de l'ordre du microgramme. Le soufre (libre ou combiné) dans les substances organiques est oxydé complètement en atmosphère d'oxygène sur une toile de platine, catalyseur, après une combustion préliminaire incomplète dans l'air. Les oxydes du soufre sont rassemblés sur une toile d'argent à 550°. On purge l'appareil de l'oxygène par un courant d'azote puis le sulfate d'argent est chauffé dans un courant d'hydrogène en donnant de l'hydrogène sulfuré qui est rassemblé dans une solution alcaline d'acétate de zinc et dosé ensuite par spectrophotométrie par la méthode au bleu de méthylène.La récupération du soufre entre 5 et 40g atteint 100±5%. La méthode demande moins de 25 minutes pour un dosage individuel et reste valable pour les teneurs descendant jusqu'à 1g de soufre dans les composés organiques de toutes natures. On peut utiliser des échantillons solides, liquides ou gazeux.相似文献
132.
Iwao Ojima Mitsuru Nihonyanagi Tetsuo Kogure Miyoko Kumagai Shuji Horiuchi Kimiyo Nakatsugawa Yoichiro Nagai 《Journal of organometallic chemistry》1975,94(3):449-461
The hydrosilylation of various carbonyl compounds such as simple aldehydes, simple ketones, α,β-unsaturated carbonyl compounds, α-diketones, acyl cyanides and ketones having an electron-withdrawing group on the α-carbon using tris(triphenylphosphine)chlororhodium as a catalyst is described. Solvolysis of these silyl ethers and silyl enol ethers afforded the corresponding reduced products. The hydrosilylation of α,β-unsaturated carbonyl compounds was found to proceed by 1,4-addition. An oxidative adduct of triethylsilane to the rhodium-(I) complex was obtained as a reaction intermediate. The structure of the adduct was discussed on the basis of its IR and far-IR spectra. 相似文献
133.
The asymmetric allylation reactions of aldehydes catalyzed by a 10 mol % bisoxazoline complex bearing a phosphine oxide moiety, which was newly designed and synthesized from l-serine, afforded the corresponding homoallylic alcohols in 48-74% yields with 39-86% ee. The reaction proceeds with the dual activation of the aldehyde and allylsilane by the Lewis acid and base of the catalyst. The evidence for the activation of the allylsilane was clarified by the 31P NMR spectra. 相似文献
134.
A new acetylenic compound from the rhizomes of Atractylodes chinensis and its absolute configuration
Nakai Y Sakakibara I Hirakura K Terabayashi S Takeda S 《Chemical & pharmaceutical bulletin》2005,53(12):1580-1581
A new acetylenic compound "atractyloyne", (3S,4E,6E,12E)-1-isovaleryloxy-tetradeca-4,6,12-triene-8,10-diyne-3,14-diol (1) was isolated from the rhizomes of Atractylodes chinensis (Compositae) together with a known compound (4E,6E,12E)-3-isovaleryloxy-tetradeca-4,6,12-triene-8,10-diyne-1,14-diol (2). These structures were determined on the basis of the spectroscopic data and chemical evidence, and the absolute configuration of 1 was established by the modified 2-methoxy-2-trifluoromethylphenylacetic acid (MTPA) method. 相似文献
135.
Iwao Omae 《Angewandte Chemie (International ed. in English)》1982,21(12):889-902
In this review article complexes of the type XnM—R are dealt with in which a σ-bonded organic ligand R is additionally linked by a π-bond with the metal M. In other words, the complexes contain metallacycles with three and a half, four and a half, five and a half members, etc. Well-Known five and a half membered ring systems are those with 4-pentenyl, 1,4-pentadienyl, norbornyl norbornenyl, cyclooctenyl, and endo-dicyclopentadienyl ligands. Metallacycles of this size are strain-free and stable. Donor ligands such as amines and phosphanes can displace the coordinated double bond of the π-ligand from the metal. This C?C double bond is lengthened from ca. 133 pm to 136–146 pm by the coordination. 相似文献
136.
Toshiyuki Kohara Hiroshi Tanaka Koreichi Kimura Hideki Horiuchi Kohji Seio Masafumi Arita Tetsuya Fujimoto Iwao Yamamoto 《Journal of heterocyclic chemistry》2002,39(1):163-171
A new series of 4‐(4‐methylpiperazin‐1‐yl)thieno[2,3‐b][1,5]benzoxazepines 1a‐k has been synthesized from 4‐bromo‐2‐methylthiophene 6 or ethyl 2‐amino‐4,5‐dimethyl‐3‐thiophencarboxylate 10 . Preparation of the key intermediate thieno[2,3‐b][1,5]benzoxazepine‐4(5H)‐ones 4a‐i, 4k were carried out by treatment of 2‐bromo‐N‐(2‐hydroxyphenyl)‐3‐thiophencarboxamides 5a‐i, 5k with potassium carbonate in DMSO. Compounds 1 are thienoanalogues of loxapine, a potent antipsychotic drug. Of these compounds, the neu‐roleptic activity of 2‐methyl‐4‐(4‐methylpiperazin‐l‐yl)thieno[2,3‐b][1,5]benzoxazepine 1a (R1, R3=H, R2=CH3) demonstrated potent antipsychotic activity. 相似文献
137.
Tohru Saitoh Nobutoshi Ojima Hitoshi Hoshino Takao Yotsuyanagi 《Mikrochimica acta》1992,106(1-2):91-99
The partition constants (K
d) have been estimated for nitrophenols, thiazolylazo dyestuffs and metal chelate compounds into the sodium dodecyl sulfate (SDS) micellar phase at an ionic strength of 0.10M [(H+, Na+)Cl–] and at 20 °C. The equilibrium partition data obtained by batch-wise solution spectrophotometry (equilibrium shift method) agree well with those by the micellar electrokinetic capillary chromatography (MECC) with the SDS micellar pseudo-stationary phase. The MECC clearly discriminates a very small difference (0.03) in the logK
d values of some metal chelates. The plot of theK
d values with the van der Waals volume of the solute molecules obviously shows the leveling-off of theK
d values over solute size near 110 ml/mol, which seems to be consistent with the results obtained in the Triton X-100 micellar system. This phenomenon arises most probably from the rigidity of the micellar pseudo-phase (a micellar volume-constraint effect) in sharp contrast with true two-phase partitioning such as solvent extraction systems. 相似文献
138.
The construction and performance of an enzyme electrode as an amperometric sensor of xanthine and hypoxanthine is described. Xanthine oxidase has been immobilized in a conductive redox polymer, poly(mercapto-p-benzoquinone), by means of an electropolymerization of mercaptohydroquinone in the presence of the enzyme. An Au-electroplated glassy carbon electrode coated with the resulting polymer film functioned well as a direct response type of sensor, where the polymer chain served as a conductive molecular chain between the active sites in the enzyme and the substrate electrode. Response characteristics as well as kinetic parameters have been evaluated. 相似文献
139.
Tetsuya Takeya Hirohisa Doi Tokutaro Ogata Tsuyoshi Otsuka Iwao Okamoto Eiichi Kotani 《Tetrahedron》2004,60(30):6295-6310
A simple method for the direct synthesis of 2,2′-binaphthols 2 and dinaphtho[1,2-b;2′,1′-d]furans 3 under mild conditions was developed, utilizing a biaryl coupling reaction via electron donor-acceptor complexes of 1-naphthols with SnCl4. Heating of the complex in a sealed tube for (18-24 h) afforded the corresponding o-o coupled product 2 in excellent yield. Prolonged reaction (56-65 h) under the same conditions afforded 3 in high yield in one step. We also found that in the case of α-naphthol without substituents other than a hydroxyl group at the C-1 position, regioselective o-o coupling reaction proceeded. The products 2a, 2b and 2g should be useful as synthetic intermediates for naturally occurring 3,3′-bijuglone, 3,3′-biplumbagin and elliptinone. 相似文献
140.
Iwao Suzuki Akiyo Yamauchi 《Journal of inclusion phenomena and macrocyclic chemistry》2006,54(3-4):193-200
Pseudo[3]rotaxane type complexation of α- and β-cyclodextrins (α- and β-CDs, respectively) with N,N′-Diheptyl-4,4′-bipyridinium (diheptyl viologen; HV2+) was investigated. A spectral displacement method using p-nitrophenol as a dye revealed that α-CD and HV2+ formed a 2:1 host-guest complex with stability constants being 3280 and 976 M−1 as the first and second steps of complexation, respectively. 1H-NMR spectra strongly indicated that α-CD accommodated the heptyl groups of HV2+. Although previous studies based on circular dichroism spectroscopy suggested the primary hydroxy side of α-CD faced to the positively charged bipyridinium moiety od HV2+, 2D-NMR studies clearly demonstrated that the secondary hydroxy side of α-CD faced to the bipyridinium moiety. β-CD also formed a 2:1 complex with HV2+ with a similar fashion. 相似文献