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101.
Aromatization of the title compound with selected acidic catalysts has been investigated. It has been established that depending upon the reaction conditions trienone 2,1 -methyltrienone3, dienone 4, diacetoxyketone5 or dione 6 are formed as the major products. Dienone 4 and dione 6 are the main compounds of the reactions of tosyloxyketone 10 with KHSO4 and HBraq, respectively. The reaction of acetoxyketone 8 with HBraq furnishes epimeric 3-bromoketones 12 and 13 in the ratio about 1:1. 相似文献
102.
Janusz Slawiski Marian Elbanowski‡ Danuta Slawiska 《Photochemistry and photobiology》1980,32(2):253-260
The spectral distribution of the chemiluminescence, fluorescence and phosphorescence of tryptophan aqueous solutions irradiated with high and low pressure mercury lamps has been measured. The blue emission bands in the region of 380–520 nm observed both in the chemi- and photoluminescence, as well as an absorbance increase at 230 and 330 nm, indicate oxidative degradation of tryptophan leading to the formation of derivatives of N-formylkynurenine, xanthurenic and anthranilic acids. Red emission bands at 630 and 705 nm in the spectrum of the chemiluminescence, an enhancement of light intensity by D2 O and its decrease by NaN3 and DABCO suggest a partial contribution of O2 (1 Δg ) to the photooxidation and chemiluminescence of tryptophan. The enthalpy of the exergonic reactions, leading to the formation of luminescing products, was calculated to average -270 kJ-mol. 相似文献
103.
Bogusław Bobrański 《Mikrochimica acta》1956,44(12):1735-1746
Zusammenfassung Das vom Verfasser undE. Sucharda schon 1928 angewandte Prinzip, die durch das Verhalten der Substanz beim Erhitzen bewirkten Druckschwankungen im Verbrennungsrohre zum Zwecke der automatischen Regulierung der Vergasungsgeschwindigkeit der Substanz bei der Elementaranalyse auszunutzen, wurde bei der Konstruktion einer neuen, elektrisch betriebenen, automatischen Apparatur angewandt. Hierbei wird das mit der Substanz gefüllte Mikroschiffchen mittels eines elektrischen Hochfrequenzgenerators erhitzt. Der Stromzufluß zu dem Hochfrequenzgenerator wird durch die erwähnten Druckschwankungen einoder ausgeschaltet. Die Verbrennung verläuft dann bei praktisch konstantem Druck im Verbrennungsrohre, also auch bei konstantem Sauerstoffüberschuß. Die neue Apparatur wird an Hand beigefügter Abbildungen beschrieben. Als Absorptionsmittel für Stickstoffoxyde werden 1 bis 2 g Bleidioxyd in einem 12 cm langen Porzellanschiffchen bei 190° angewandt. Die Absorption des Wassers erfolgt durch wasserfreies Kobaltchlorid, die der Kohlensäure ausschließlich durch Ascarit. Die Sauerstoffgeschwindigkeit im Verbrennungsrohre beträgt 8 ml pro Minute. Bei Substanzen, die mehr als 10% N enthalten, wird zwischen den Kohlensäureabsorptionsapparat und den Wasserabsorptionsapparat ein mit Mangandioxyd gefüllter Apparat eingeschaltet.
Summary The principle used by the author andE. Sucharda as early as 1928, which employs the variations in pressure in the combustion tube resulting from the behavior of the substance when heated, for automatically regulating the rate of gasifying the substance was applied in the construction of a new electrically operated automatic apparatus. The micro boat charged with the sample is heated by means of a high frequency generator. The flow of current to the high frequency generator is switched on and off by the variations in pressure mentioned above. The combustion then proceeds at practically constant pressure in the combustion tube, and even when there is a constant excess of oxygen. The new apparatus is described in the accompanying figures. The nitrogen oxides are absorbed in 1 to 2 grams of lead dioxide contained in a porcelain boat (12 cm long) at 190°. The absorption of the water is by means of anhydrous cobalt chloride, while the carbon dioxide is taken up in ascarite. The speed of the oxygen in the combustion tube is 8 ml per minute. In the case of samples that contain more than 10% nitrogen, an apparatus filled with manganese dioxide is placed between the carbon dioxide absorber and the apparatus for taking up the water.
Résumé Le principe de l'utilisation des variations de pression qui se produisent dans un tube à combustion en analyse élémentaire, lors du chauffage de la substance, a été utilisé dès 1928 par l'auteur etE. Sucharda pour la régulation automatique de la gazéification de cette substance. Il a été appliqué à la construction d'un nouvel appareil automatique commandé électriquement. La micronacelle qui contient la substance est chauffée électriquement à l'aide d'un générateur de courant de haute fréquence. Les variations de pression pendant la combustion provoquent l'ouverture ou la fermeture du circuit d'alimentation de ce générateur. Il en résulte que la combustion est effectuée à pression pratiquement constante ainsi qu'à excès d'oxygène constant. Ce nouvel appareil est décrit sur les figures de la publication.On utilise 1 à 2 grammes de bioxyde de plomb disposés dans une nacelle de porcelaine de 12 cm de longueur, portée à 190° pour absorber les oxydes de l'azote. L'eau est absorbée par du chlorure de cobalt anhydre et l'anhydride carbonique exclusivement par de l'ascarite. Le débit du courant d'oxygène dans le tube de combustion est de 8 ml par minute. Pour les substances contenant plus de 10% d'azote, on intercale un absorbeur à bioxyde de manganèse entre l'absorbeur à anhydride carbonique et l'absorbeur à eau.相似文献
104.
Acidolytic cleavage of unsymmetrically substituted dithioacetal monoxides, ArCH(SR)S(O)Me has been used to prepare linear unsymmetrical disulfides RSSMe. Disproportionation was suppressed by the addition of a small amount of benzyl mercaptan. The required starting materials were conveniently obtained from appropriately substituted sulfines ArC(=SO)SR and methyl lithium. The following disulfides were prepared: R =n-C4H9 (73.5%), n-C7H15 (78%), Ph (77.3%), AcO(CH2)10 (81.5%).The unsymmetrical dithioacetal PhCH(SEt)SC7H15-n gave upon oxidation with one equivalent of peracid a mixture of two dithioacetal monoxides which on treatment with HClO4 led to three disulfides. This result is discussed in term of the mechanism of acidolysis. 相似文献
105.
Two new Schiff base macrocycles - a 4+4 condensation product and a meso-type 2+2 condensation product - were obtained in a reaction of trans-1,2-diaminocyclohexane and 2,6-diformylpyridine. Reduction of these compounds led to the corresponding 4+4 and 2+2 macrocyclic amines. The macrocycles were characterised by NMR spectroscopy and electrospray mass spectrometry. The symmetry and stereochemistry of these macrocycles, as well as of new 3+3 and 4+4 diastereomers identified in solution, has been established. X-Ray structures of the 2+2 and 4+4 Schiff base macrocycles confirm the configurations determined on the basis of spectroscopic investigations. The crystal structures reveal that the centres of the square-shaped 4+4 macrocycles form channels as a result of columnar stacking. 相似文献
106.
Kabatc J Jedrzejewska B Orliński P Paczkowski J 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2005,62(1-3):115-125
The photophysical and photochemical properties of p-substitued 2-styryl-ethylbenzothiazolium iodides, possessing different electron-withdrawing or electron-donating groups are described. The dyes were prepared by the condensation of 3-ethyl-2-methylbenzothiazole salts with p-substituted benzaldehydes. The synthesis of suitable substrates is presented as well. We describe here the absorption, emission spectra and the luminescence quantum yield of hemicyanine dyes (SH) measured in 11 different organic solvents of varying polarity. Molecular structure of the synthesized dyes was established by (1)H NMR, electronic absorption and fluorescence spectrometry. The spectral data confirmed that all the compounds exist in E-configuration of their styryl residues. The planar molecular conformation is typical for the compounds with five-membered side aromatic moieties (for example benzothiazole). The compounds possessing N-alkyl substituent in phenyl ring, in contrast to the compounds with other substituents, exhibit low fluorescence quantum yield in THF solution. This indicates that for N-alkyl derivatives the non-radiative processes are much more effective than the radiative ones. The electronic absorption and fluorescence emission spectra of tested dyes demonstrate high sensitivity to the nature of substituent introduced into the aromatic ring. 相似文献
107.
Silica xerogels with different structures and morphology, synthesized using a sol-gel procedure, were used as a carrier of vanadium catalysts (VOCl3/AlEt2Cl) for ethylene polymerization. Two techniques of catalyst synthesis were applied: slurry impregnation and gas-phase adsorption and the relevant polymerization methods were then employed. The effect of the carrier structure and morphology on the vanadium loading in the catalysts, the catalyst’s activity and kinetic stability were investigated. 相似文献
108.
The reactions of dialkylaluminium acetylacetonates, R2Al(acac),(where R = CH3, C2H5 and i-C4H9; I–III) with Lewis bases Et2O, THF, Py, 2,6-dimethylpyridine (DMP), DSMO and HMPT, have been studied. The reaction was found to proceed according to the equation: With strong bases (B) the reaction is shifted completely to the right, with bases of moderate strength an equilibrium is established and with weak bases the reaction is shifted completely to the left. The reaction rate constant k1 depends on R and increases in the order i-C4H9 < C2H5 < CH3. The reaction starts from the formation of the complex R2Al(acac)-B (consisting of a five-coordinated aluminium atom) and its further dissociation. The reaction mechanism is discussed. 相似文献
109.
W. K. Jóźwiak T. P. Maniecki A. Basińska J. Góralski R. Fiedorow 《Kinetics and Catalysis》2004,45(6):879-889
This paper is focused upon the influence of potassium on the reduction behavior and catalytic properties of Fe2O3, Ru/Fe2O3 and Ru/(K)Fe2O3 catalysts for the water gas shift (WGS) reaction. The effect of promotion by potassium is attributed to stabilization of a highly dispersed ruthenium phase on the iron oxide surface. The hydrogen reduction behavior of Fe2O3 catalysts is strongly influenced by time-pressure dependent processes and comprises two or three heavily overlapped TPR peaks which can be ascribed to the following stages of the iron(III) oxide reduction 3Fe2O3 2Fe3O4 6FeO 6Fe. The appearance of FeO as an intermediate phase was confirmed by XRD. The presence of ruthenium(IV) oxide substantially changes the kinetics of the reduction process. In the case of potassium-doped catalysts, the reduction of Fe2O3 is substantially different and is assigned to the reduction phase of KFeO2. Both ruthenium and potassium have a promoting effect on the catalytic activity for the WGS reaction.From Kinetika i Kataliz, Vol. 45, No. 6, 2004, pp. 930–941.Original English Text Copyright © 2004 by Jówiak, Maniecki, Basiska, Góralski, Fiedorow.This article was submitted by the authors in English. 相似文献
110.
Low molecular weight tri-podal biphenyl- and benzoate-type mesogens [C6H5C6H4O(CH2)5SiMe2CH2CH2SiMe2]3CH (4), [C11H23O(C6H4)2O(CH2)5SiMe2]3CH (5) and [MeOC6H4OC(O)C6H4O(CH2)5SiMe2]3CH (6) (C6H4 = 1,4-phenylene) were obtained, from branched silyl substituted methane precursors [CH2CH(Me)2Si]3CH (1) and (HMe2Si)3CH (2). The biphenyl-containing ones (4) and (5) were converted into terminal alkenes, which were subsequently hydrosilylated with poly(methylsiloxanes). The polymer derived from (5) exhibited mesomorphic properties. Such systems have the potential to significantly increase the density of liquid crystal rod-like structures in side chains of linear polymers (or dendritic liquid crystal polymers). 相似文献