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  • Chemistry  (91)
  • General Chemistry  (38)
  • 61.70  (3)
  • Pyridines
  • 1
    Electronic Resource
    Electronic Resource
    Positron lifetimes and annihilation lineshape in Cd and au from 4.2 K to the melting points (1977)
    Springer
    Applied physics 12 (1977), S. 59-67 
    Details
    ISSN: 1432-0630
    Keywords: 61.70 ; 81
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract By means of an integrated source-specimen technique the temperature dependence of positron lifetimes and annihilation lineshapes has been measured, on the same specimens of gold and cadmium from 4.2K to the melting points, and also in electronirradiated and quenched gold. The anomalous temperature dependence of positron annihilation at intermediate temperatures (200 to 350 K in Cd, 270 to 750 K in Au) discovered by Lichtenberger, Schulte, and MacKenzie is confirmed. The data are incompatible with the idea that the intermediate temperature dependence is due to thermal expansion. They are well explained by an extension of the trapping model which includes the formation of metastable self-trapped positrons. From lineshape measurements after electron irradiation at 180 K and after quenching it is deduced that the trapping rate of positrons at vacancy-type defects in Au is temperature independent below room temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00900069
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  • 2
    Electronic Resource
    Electronic Resource
    The positron beam at the stuttgart pelletron accelerator and its applications toβ +γ positron lifetime measurements (1987)
    Springer
    Applied physics 43 (1987), S. 261-267 
    Details
    ISSN: 1432-0630
    Keywords: 78.70 ; 61.70 ; 07.77
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract A slow-positron source has been installed in the therminal of an electrostatic 6.5 MeV accelerator and provides a monoenergetic positron beam in the few-MeV range. It will be used to operate a “fast” positron lifetime spectrometer based onβ + γ coincidences. The properties of the beam, the expected performance of the spectrometer, its advantages over conventionalγγ lifetime measurements, a number of intended applications, as well as recent positron-electron scattering experiments and plans for positron channelling and channelling-radiation studies are outlined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00635181
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  • 3
    Electronic Resource
    Electronic Resource
    Synthese neuartig substituierter Pyridazin-6(1H)-one (1995)
    Springer
    Monatshefte für Chemie 126 (1995), S. 341-347 
    Details
    ISSN: 1434-4475
    Keywords: Chloroacetic acid chloride ; Phenylhydrazono acetamides ; Pyridines ; Pyridazin-5-ylpyridinium chlorides ; 4,5-Diamino-pyridazin-6(1H)-ones
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Arylhydrazono acetamides1 react with chloroacetic acid chloride to give N-chloroacetyl derivatives2. Subsequent reaction with pyridines followed by ring closure yield 1-(4-amino-6-oxo-pyridazin-5-yl)-pyridinium chlorides3. Analogously, 1-(6-oxo-pyridazin-5-yl)-pyridinium chloride (5) and 6-oxo-5-pyridinio-pyridazin-4-olate (4) are formed from phenylhydrazono derivatives and pyridine. Treatment of3 and4 with hydrazinium hydrate gives 4,5-diamino-6-oxo-pyridazin-3-carbohydrazides6 and 5-amino-4-hydroxy-pyridazin-6(1H)-one (8). An analogous ring cleavage of3e and5 gives rise to 4,5-diamino- and 5-amino-pyridazin-6(1H)-ones7. On treatment of the pyridinium salts3 with caustic soda in water, nucleophilic addition of the amino group to the pyridinium ring takes place and stable dehydrated products9 are isolated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00816103
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  • 4
    Electronic Resource
    Electronic Resource
    Irradiation-induced atomic defects in SiC studied by positron annihilation (1995)
    Springer
    Applied physics 61 (1995), S. 51-53 
    Details
    ISSN: 1432-0630
    Keywords: 61.70 ; 61.80 ; 78.70
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The present paper reports on positron lifetime measurements on atomic defects in SiC after low-temperature (80 K) electron irradiation of low (0.47 MeV) and high (2.5 MeV) electron energies and doses from 1.8×1017 to 1.9×1019 e/cm2 as well as after subsequent isochronal annealing up to 1900 K. For these studies the single crystals of nitrogen doped (2–3×1018 cm−3) SiC grown by a modified Lely technique with hexagonal structure (6H polytype) were used. According to the positron lifetime measurements, very different types of vacancy-like positron traps are introducted after irradiation with electrons of either low or high energy. The formation of defect agglomerates and their decay at high temperatures is studied during isochronal annealing and related to earlier studies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01538210
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  • 5
    Electronic Resource
    Electronic Resource
    Syntheses with pyridinium and sulfonium salts of acylated β-enaminonitriles (1995)
    Springer
    Monatshefte für Chemie 126 (1995), S. 711-723 
    Details
    ISSN: 1434-4475
    Keywords: Malononitrile ; Benzoles ; Pyridines ; Thiophenes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Pyridinium- und Sulfoniumsalze2a–e, die aus 3-Amino-2-(α-halo-acetyl)-crotonsäurenitril und 3-Amino-2-(α-halo-acetyl)-zimtsäurenitril hergestellt werden können, reagieren mit Malonsäuredinitril in Gegenwart einer Base zu 3-Amino-2-pyridinio-phenolaten3a,b und 3-Amino-2-sulfonio-phenolaten3c–e. In Analogie wurden 3-Amino-2-(diethyloxyphosphoryl)-phenol5a und 3-Amino-2-(p-tolyl-sulfonyl)-phenol5b erhalten. 2,3-Diamino-phenole6a,b werden aus den Pyridiniumsalzen3a,b gebildet. Das Verhalten der Pyridiniumsalze2a,b gegenüber Heterokumulenen ist untersucht worden. Cyanamid führt zum (2-Amino-4-hydroxy-pyrid-3-yl)-pyridiniumsalz8c. Phenylisothiocyanat liefert die 3-Pyridinio-2-thioxo-pyridin-4-olate9a,b. In Abhängigkeit vom Substituenten in der Position 6 entsteht bei der Reaktion mit Schwefelkohlenstoff ein 3-Pyridinio-2-thioxo-pyridin-4-olat10 oder ein 3-Pyridinio-2-thioxo-thiopyran-4-olat11. Phenylisocyanat reagiert zum Pyrimidin-2,4-dion12 unter Verlust von N-Methyl-pyridiniumchlorid. S-Methylierung von9a und Spaltung des Pyridiniumringes ergibt das 3-Amino-2-methylthio-pyrid-4-on14. Die Verbindungen wurden1H- und13C-NMR-spektroskopisch untersucht.
    Notes: Summary Pyridinium and sulfonium salts2a–e which can be prepared from 3-amino-2-(α-haloacetyl)-crotonitriles and 3-amino-2-(α-halo-acetyl)-3-phenyl-acrylonitriles react with malononitrile in the presence of a base to 3-amino-2-pyridinio-phenolates3a,b and 3-amino-2-sulfonio-phenolates3c–e. In an analogous way, 3-amino-2-(diethyloxyphosphoryl)-phenol5a and 3-amino-2-(p-tolyl-sulfonyl)-phenol5b have been prepared. 2,3-Diamino-phenoles6a,b are formed from the pyridinium salts3a,b. The behaviour of the pyridinium salts2a,b towards heterocumulenes has been investigated. Cyanamide leads to the (2-amino-4-hydroxy-pyrid-3-yl)-pyridinium salt8c. Phenylisothiocyanate gives the 3-pyridinio-2-thioxo-pyridin-4-olates9a,b. Carbon disulfide gives rise to 3-pyridinio-2-thioxo-pyridin-4-olate10 or 3-pyridinio-2-thioxo-thiopyran-4-olate11, depending on the substituent at the 6-position. Phenylisocyanate reacts to the pyrimidin-2,4-dione12 with loss of N-methyl-pyridinium chloride. S-methylation of9a and cleavage of the pyridine moiety yields the 3-amino-2-methylthio-pyrid-4-one14. The structures were investigated by1H and13C NMR spectroscopy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00807162
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  • 6
    Electronic Resource
    Electronic Resource
    Amino-thieno[2,3-c]pyrazole und Amino-thieno[2,3-b]pyrrole (1995)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 337 (1995), S. 472-477 
    Details
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Amino-thieno[2,3-c]pyrazoles and Amino-thieno[2,3-b]pyrrolesThe synthesis of thieno[2,3-c]pyrazoles and thieno[2,3-b]pyrroles is described. From the dithioliumsalt (1) and potassium hydroxide the potassium-(2,2-dicyan-1-methylthio-ethen-1-yl)-thiolate (2) is formed. This reacts with hydrazine hydrate to form the 3-amino-5-thioxo-pyrazol-4-carbonitrile (3) S-Alkylation with α-chlorocarbonyl compounds yielding (6a-c) leads via Thorpe-Ziegler-cyclization to 3,4-diamino-thieno[2,3-c]pyrazoles (9) if the position 1 is alkylated (8). Acetyl acetone yields 2-mercapto-pyrazolo[1,5-a]pyrimidine (5). After S-alkylation (10a-d) are immediately cyclized to thieno [2′,3′:3,4]pyrazolo[1,5-a]pyrimidine (11a-d). The ketone (6a) can be cyclized to the pyrazolo [5,1-b]thiazole (12). 3 reacts with oxalyl chloride to form the 2,3-dioxo-6-thioxo-imidazo[1,2-b]pyrazole (13) of which S-phenacyl derivative (14) because the NH-proton cannot be cyclized. The 5-amino-3,4-dicyano-pyrrol-2-thiolate (16) shows the analogous behaviour. The S-alkylation is followed by cyclization, and 3,5-diamino-thieno[2,3-b]pyrroles (18a-b) arise. Reaction of 5-amino-2-alkylthio-pyrrol-3,5-dicarbonitrile (17) with acetyl acetone provides pyrrolo[1,2-a]pyrimidine (20a-c) which can be cyclized to form thieno[3′,2′:4,6]pyrimidines (21a-c) very easily.
    Additional Material: 6 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.199533701101
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  • 7
    Electronic Resource
    Electronic Resource
    Zur Synthese von 3-Amino-pyrrolen durch Thorpe-Ziegler-CyclisierungHerrn Prof. Dr. K. Schwetlick zum 60. Geburtstag gewidmet (1992)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 334 (1992), S. 491-496 
    Details
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: On the Synthesis of 3-Amino-pyrroles by Thorpe-Ziegler-CyclizationN-Aryl and alkylaminomethylene cyanacetic acid derivatives 1 react with α-halogencarbonyl compounds 2 in the presence of potassium carbonate/sodium ethoxide to yield the substituted 3-amino-pyrroles 6. Using the same principle of cyclization pyrrole derivatives 6 can also be obtained by reaction of β-chloro- and β-alkoxymethylenemalononitriles 4 with β-aminocarbonyl compounds 5. From the malononitrile derivatives 1 containing the methylthio group in the β-position, and α-halogen ketones 7, the 2-dicyanomethylene oxazolines 8 arise which undergo alkoholysis by treatment with sodium alkoxide to form the 3-amino-5-alkoxy-pyrrole derivatives 9.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19923340608
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  • 8
    Electronic Resource
    Electronic Resource
    Neue Synthese von substituierten 4-Amino-chinazolinen und deren Heteroanalogen (1996)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 338 (1996), S. 206-213 
    Details
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: New Synthesis of Substituted 4-Amino-quinazolines and Their HeteroanalogaN-Chloracetyl-anthranilonitriles react with potassium thiocyanate in the presence of alcohol to the (4-aminoquinazolin-2-yl-thio)-acetic acid ester (5). In the presence of water or primary amine the acetic acid derivative (6) or the acetic acid amide derivatives (7) are obtained. 2,4-Diaminoquinazolines (8) arise if vigorous reaction conditions are employed. With 2-chloracetylamino-cyclopent-1-en-carbonitrile as starting material the pyrimidines (11) are formed from the reaction with potassium thiocyanate. Analogously, (4-pyrimidyl-2-yl-seleno)-acetic acid ester (12) and (thiazolo[4,5-d]pyrimid-2-yl-seleno)-acetic acid derivatives (16) can be prepared with potassium selenocyanate. N-Chloracetyl derivatives of 5-membered heterocycles with enamino-nitrile structure (13, 15, 18, 20) react with potassium thiocyanate to yield thieno[2,3-d]-, thiazolo[4,5-d]-, pyrrolo[2,3-d]-, furo[2,3-d]- and pyrazolo[4,3-d]pyrimidines (14, 16, 19a, 19b, 21).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19963380144
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  • 9
    Electronic Resource
    Electronic Resource
    Hydrogels based on 2.2.3.3.4.4.4.-heptafluorobutyl methacrylate (1992)
    Weinheim : Wiley-Blackwell
    Acta Polymerica 43 (1992), S. 335-342 
    Details
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Hydrogele (vernetzte Polymere mit definiertem Wassergehalt) wurden aus hydrophilen Methacrylaten und Perfluorbutylmethacrylat durch radikalische Polymerisation und nachfolgende Quellung in gepufferter isotonischer Natriumchloridlösung hergestellt. Die erhaltenen Hydrogele wurden durch ihre lineare Quellung, den Wassergehalt, den Brechungsindex, den Gehalt an extrahierbaren Bestandteilen, ihre Transparenz für sichtbares Licht sowie durch ihre Sauerstoffpermeation charakterisiert. Derartige Hydrogele sind interessant als Materialien für Kontaktlinsen.
    Notes: Hydrogels (crosslinked polymers with a defined content of water) from hydrophilic methacrylates and perfluorobutyl methacrylate were prepared by radical polymerization, followed by swelling in buffered isotonic sodium chloride solution. The obtained hydrogel samples have been characterized by their linear expansion to hydration, weight-percent hydration, refractive index, extractables, percent transmission of visible light, and oxygen permeability. Such hydrogels are interesting as contact lens materials.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/actp.1992.010430608
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  • 10
    Electronic Resource
    Electronic Resource
    Mischorgan zum Vergleichmäßigen laminarer Strömung in engen Rohren (1966)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 38 (1966), S. 994-995 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cite.330380912
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