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991.
The mass spectra of twenty-six commercially available medicinal phenothiazines have been determined at high resolution. In each compound, the side chain attached to the 10-position of the phenothiazine ring contains nitrogen and fission of the C? C bond α to this nitrogen gives in most cases the base peak. Some of the compounds are also substituted at the 2-position and this substituent generally remains intact, though some substituents such as acetyl, propionyl, methoxyl and methylthio can undergo fragmentation. Fragmentations fall into three groups; those which give ions representing a part of the side chain; those which give ions representing the intact phenothiazine ring with part of the side chain attached; those which give ions representing a partially fragmented ring system.  相似文献   
992.
Irradiation of 3,19-dioxo-17β-acetoxy-Δ4-androstene ( 2 ) at room temperature in either of its two absorption bands centered at about 245 and 315 nm, respectively, led to products 21, 22 , and 23 (Chart 3). Compounds 21 and 22 result from rearrangements involving intramolecular formal 1,2- (→ 21 ) and 1,3-shifts (→ 22 ) of the angular formyl group, and the formation of compound 23 proceeds through the elimination of the formyl radical and the incorporation of a hydrogen from the medium. Evidence favors the latter process to be a secondary radical reaction rather than a primary photochemical step.  相似文献   
993.
The solubility products for some rare earth hydroxides and their temperature dependence have been shown. Greater solubility is shown for larger atomic radii and for lower temperature.  相似文献   
994.
Summary The conductivity of polystyrene solutions (2 g/l) in decahydronaphthalene (decaline), ethylbenzene and dichloroethane as a function of temperature, and of polymethylmetacrylate in benzene (2 g/l) and acetone as a function of both temperature and concentration ((0,25–4 g/l) was investigated. Two kinds of the conductivity-temperature dependence could be observed. One, obeing the Arrhenius law, the other leading to maximum values of the conductivity in the transition temperature ranges. That behaviour is mainly dependent on the polarisability of the components. The tacticity of the polymers is important too.
Zusammenfassung Die elektrische Leitf?higkeit von Polystyroll?sungen (2 g/l) in Decahydronaphthalin (Dekalin), ?thylbenzol und Dichlor?than als Temperaturfunktion und Polymethylmethacrylatl?sungen in Benzol und Aceton als Konzentration (0,25–4 g/1) und Temperaturfunktionen wurde untersucht. Der Temperaturbereich entspricht dem bekannten Konformationsübergangsbereich. Zwei Arten von Leitf?higkeits?nderungen bei Erw?rmung wurden beobachtet. Die eine entspricht der Arrhenius-Gleichung für Temperatur?nderungen mit einem Knick im Bereich der Konformationsumwandlung, die zweite zeigt ein Leitf?higkeitsmaximum in demselben Temperaturbereich. Dieses Verhalten scheint haupts?chlich von der Polarisierbarkeit der Komponenten abh?ngig zu sein. Neben der Polarisierbarkeit spielt bei diesen Erscheinungen die Taktizit?t der Polymeren eine wichtige Rolle.


With 8 figures and 3 tables  相似文献   
995.
The compounds Ba4Fe2S6[S23(S2)13] and Ba3.6Al0.4Fe2S6[S0.6(S2)0.4], designated I and II, were prepared by reacting BaS, Fe, and S powders and Al foils in graphite containers sealed in evacuated quartz ampoules at approximately 1100°C. The crystal structure of I was determined using 1682 independent, nonzero X-ray reflections, while 3589 were used for II. They are triclinic, Al:
a=9.002(2)A?,b=6.7086(8)A?,c=24.658(4)A?α91.49(2)°,
β=105.10(2)°y=90.74(2)°,ψcalc=4.15g/cm3,for I:
a=8.993(6)A?,b=6.708(7)A?,c=24.70(1)A?α91.11(6)°,
β=105.04(6)°y=90.90(9)°,ψcalc=3.90g/cm3,for II:
BaS6 trigonal prisms share edges to form distorted hexagonal rings which form one-dimensional chains leaving two free lateral edges. The chains link in a stairstep manner with the rings offset along the [301] direction. These stairsteps join in a complicated manner to form a three-dimensional network. Fe ions are in two sites forming isolated FeS4 tetrahedra and isolated Fe2S6 dimers by edge-sharing tetrahedra. The Al substitution occurs in the trigonal prisms which have free edges with Al replacing Ba. Room-temperature Mössbauer isomer shifts are 0.20 mm/sec. for I and 0.30 mm/sec for II. These data indicate that upon Al substitution charge compensation occurs by reducing Fe3+. Valence calculations indicate that Fe in edge-sharing tetrahedra are reduced while the Fe in the isolated tetrahedron remains unchanged. The effective charge distribution in the Al substituted compound is approximately Fe3+, Fe2.5+ with electron delocalization across the shared edge. Room temperature electrical resistivity is 105 ohm/cm. The compositions of the crystals are best represented by the formulas [Ba4Fe2S7]23·[Ba4Fe2S6(S2)]13 and [Ba3AlFe2S7]0.4·[Ba4Fe2S7]0.2·[Ba4Fe2S6(S2)]0.4. The replacement of a sulfide by a disulfide ion is thought to be strongly dependent on the sulfur activity during the preparation.  相似文献   
996.
Indolinone nitroxides undergo a homolytic substitution with aroyl oxyl radicals, leading to two isomers, 7-aroyloxy- and 5-aroyloxy-derivative, respectively, whose structures were assigned on the basis of the ESR hfccs and of the 1H NMR spectra of the corresponding amines. The presence of aroyl oxyl radicals in the reaction medium was demonstrated by thermal decomposition of benzoyl peroxide in the presence of aromatic acids.  相似文献   
997.
Optimum conditions have been established for formation and extraction of indium-Rhodamine complexes, and limits of detection found for fluorimetric determination of gallium and indium by means of Rhodamine dyes, using the excitation with pulsed laser and xenon arc sources.  相似文献   
998.
The pigments Luteoskyrin (Ls) and Rugulosin (Rg) might adopt a priori two extreme conformations, a planar and an angular one. To determine the predominant conformation in solution, the nature of the lowest energy transition of the chromophores and the presence of intramolecular H-bonding have been investigated. The solvent effects on electronic absorption and CD spectra indicated the π-π* nature of the lowest energy transition. Treatments of the electronic absorption results according to McRae and Kosower relations, IR absorption and PMR spectra suggested the presence of strong intra-molecular H-bonds. From these results it was concluded that Ls and Rg adopted in a variety of solvents the most planar conformation.  相似文献   
999.
The syntheses of 7′-methoxy- and 5′,7′,6-trimethoxy-coumarino(3′,4′:3,2)coumarones (IIa and IIb) are described.  相似文献   
1000.
An accurate method for the determination of inorganic sulphate in synthetic detergents has been developed. After addition of a cationic surface-active agent (cetyl pyridinium chloride) to an anionic detergent, sulphate can be determined by means of indirect titration with EDTA, using a mixture of Metalphthalein and Naphthol Green B as indicator.  相似文献   
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