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  • 550 - Earth sciences  (28)
  • Chemistry  (4)
  • diazene oxides  (2)
  • 33.80.Wz  (1)
  • 1
    Digitale Medien
    Digitale Medien
    Isotopically selective IR multiphoton dissociation of 1,3,5-trioxane (1996)
    Springer
    Applied physics 62 (1996), S. 203-212 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 33.80.Wz
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Searching for oxygen-isotope selectivity, we investigated the infrared multiphoton dissociation of the formaldehyde trimer around 10 µm, in a range where the molecule has a degenerate and a non-degenerate CO stretch vibration and a degenerate CH2 deformation vibration. In the region of the two latter, the wavelength dependence of the dissociation yield exhibits sharp structures. They were assigned ton-photon resonances (n = 2, 3, 5) by the help of the IR spectrum in the fundamental and overtone region. The O and C selectivities were very small (1.05) near the non-degenerate CO stretch band, but surprisingly large (2–4) in the CH2 deformation, which has no isotopic shift. The selectivity is not controlled by the first (n-photon) excitation step, but only by a later step. Its assignment is attempted. The pressure dependence of the dissociation is peculiar: Only after an initial decrease, the yield exhibits the usual rise with pressure. We attribute the decrease to a relaxation which perturbs the two-photon resonance.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01081126
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  • 2
    Digitale Medien
    Digitale Medien
    Nucleophilic Aromatic Substitution of Hydrogen in the Reaction of tert-Alkylamines with Nitrosobenzenes - Synthesis and NMR Study of N-(tert-Alkyl)-ortho-nitrosoanilines (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 29-35 
    Details
    ISSN: 1434-193X
    Schlagwort(e): Nitrosobenzenes ; ortho-Nitrosoanilines ; 2-Nitroso-1,3-phenylenediamines ; Nucleophilic aromatic substitution ; Oxidative nucleophilic substitution of hydrogen ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: -The reaction of primary amines bearing tertiary alkyl groups (e.g. R-NH2; R = tBu, 1-adamantyl) with nitrosobenzenes has been found to proceed by oxidative nucleophilic aromatic substitution of hydrogen, thereby affording N-(tert-alkyl)-ortho- and -para-nitrosoanilines. The replacement of hydrogen proceeds more rapidly than the replacement of ortho- or para-nitro or -bromo substituents. With p-nitronitrosobenzene, both ortho-hydrogen atoms are substituted to afford N,N′-di(tert-alkyl)-4-nitro-2-nitroso-1,3-phenylenediamines 8a,b. The addition of oxidizing agents (e.g. MnO2) increases the yield of products. 1H-, 13C-, 14N- and 15N-NMR studies have confirmed the structures of the compounds under investigation. In ortho-nitrosoanilines, the rotamer with the nitroso group syn to the amino group is favored.
    Zusätzliches Material: 3 Tab.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    A Novel Route to the 5-[2-(Diphenylphosphanyl)ethyl]-1,2,3,4-tetramethylcyclopentadienyl Ligand - Synthesis and Crystal Structure of [η5:η1-C5(CH3)4CH2CH2PPh2]ZrCl3·THF (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 1973-1979 
    Details
    ISSN: 1434-1948
    Schlagwort(e): Phosphanylethyl-functionalized cyclopentadienyl ligands ; Intramolecular coordination ; Spiro compounds ; Zirconium ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The five-step synthesis of the first transition metal complex with the C5(CH3)4CH2CH2PPh2 ligand [η5:η1-C5(CH3)4CH2CH2PPh2]ZrCl3·THF (11), starting from the known compound [2-(dimethylamino)ethyl]tetramethylcyclopentadiene (4) via 4,5,6,7-tetramethylspiro[2,4]hepta-4,6-diene (7), is reported. Lithium cyclopentadienide LiC5(CH3)4CH2CH2PPh2 (9), silylated cyclopentadiene (CH3)3SiC5(CH3)4CH2CH2PPh2 (10) and cyclopentadiene HC5(CH3)4CH2CH2PPh2 (12) were isolated and characterised as pure substances. The crystal structure of the zirconium complex 11 was established by X-ray diffraction analysis.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    Synthesis of 1-aryl-2-alkenyldiazene 1-oxides (1995)
    Springer
    Russian chemical bulletin 44 (1995), S. 897-900 
    Details
    ISSN: 1573-9171
    Schlagwort(e): diazene oxides ; alkenes ; azoxyolefines
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract 1-Aryl-2-alkenyldiazene 1-oxides were prepared by the reactions of 1-aryl-2-bromodiazene 1-oxides with olefins followed by dehydrobromination of the intermediate 1-aryl-2-(β-bromoalkyl)diazene 1-oxides by triethylamine.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00696923
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  • 5
    Digitale Medien
    Digitale Medien
    Reaction of 1-aryl-2-alkenyldiazene 1-oxides with hydrogen chloride. Novel approach to the synthesis of functionally substituted arylhydrazones (1995)
    Springer
    Russian chemical bulletin 44 (1995), S. 901-906 
    Details
    ISSN: 1573-9171
    Schlagwort(e): chlorohydrazones ; diazene oxides ; azoxyalkanes ; azoolefins
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The reaction of 1-aryl-2-alkenyldiazene 1-oxides with HCl yields arylhydrazones of α-chloroacyl chlorides, which eliminate HCl to give 1-aryl-2-(1-chloroalken-1-yl)diazenes. The latter add amines, alcohols, and carboxylic acids to give arylhydrazone chlorides with α-functional groups.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00696924
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  • 6
    Digitale Medien
    Digitale Medien
    Synthesis of Germatranyl Derivatives of Esters of Carboxylic Acids via Organometallic (Si, Ge, Sn) Reagents (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 739-746 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Germatranes ; Organotrihalogenogermanes ; Organometallic (Si, Ge, Sn) reagents ; Transmetallation ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Trialkylstannyl esters of tris(2-hydroxyalkyl)amines, N(CH2CHROSnAlk3)3 (9-11 (R = H, Me; Alk = Et, Bu), react with X3GeC(R1)(R2)COOR3 (12-17) (X = Cl or Br; R1, R2=H, Me, Ph, SiMe3, COOEt; R3=Me, Et) to give esters of α-germatranylcarboxylic acids, N(CH2CHRO)3GeC(R1)(R2)-COOR3 (1-8), in high yields. The synthesis of esters 12-17 is reported. Esters of α-germatranyldiphenylacetic acid 24 and 25 can be obtained by treatment of diphenylketene with Et3SnOMe to give in situ Et3SnC(Ph2)COOMe (23), followed by reaction with GeCl4 to give in situ Cl3GeC(Ph2)COOMe (22 and further reactions with 9 or 11, respectively. Reduction of germatrane 6 with LiAlH4 in diethyl ether leads to cleavage of the germanium-carbon bond with subsequent formation of (2-hydroxyethyl)trimethylsilane. The crystal structures of 3, 6 and 7 are reported. 1-Acyloxygermatranes 26 and 27 are obtained by treatment of 1-methoxygermatrane (28) with diphenyl- and dichloroacetic acid, respectively.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19971300611
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  • 7
    Digitale Medien
    Digitale Medien
    Synthesis, characterization, and structures of 1-(9-Fluorenyl)-germatrane and 1-(Phenylacetylenyl)germatrane (1997)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 623 (1997), S. 1144-1150 
    Details
    ISSN: 0044-2313
    Schlagwort(e): Trihalogenogermane ; Germatrane ; Transmetalation ; Crystal structure ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Darstellung, Charakterisierung und Strukturen von 1-(9-Fluorenyl)germatran and 1-(Phenylacetylenyl)germatranÜber die Synthesen der Titelverbindungen, nämlich N(CH2CH2O)3GeY (2 Y=Fluorenyl; 4 Y=PhC≡C) durch Reaktion von X3GeY (1 Y=Fluorenyl, X=Br; 5 Y=PhC≡C, X=Cl) mit N(CH2CH2OSnR3)3 (3 R=Et; 6 R=Bu) wird berichtet und die Darstellung der neuen Verbindung 1 wird beschrieben. Die Strukturen der Verbindungen wurden durch Elementaranalysen sowie mittels 1H and 13C NMR-Spektroskopie bestimmt, 2 und 4 massenspektrometrisch charakterisiert. 1, 2 und 4 wurden mit Röntgenbeugungsmethoden analysiert.
    Notizen: Syntheses of the title compounds, viz. N(CH2CH2O)3GeY (2 Y=Fluorenyl; 4 Y=PhC≡C) by the reaction of X3GeY (1 Y=Fluorenyl, X=Br; 5 Y=PhC≡C, X=Cl) with N(CH2CH2OSnR3)3 (3 R=Et; 6 R=Bu) are reported including the preparation of the new compound 1. Identity and structures were established by elemental analyses, 1H and 13C NMR spectroscopy. 2 and 4 were characterized by mass spectrometry. Single crystal structures of 1, 2 and 4 were determined by X-ray diffraction methods.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/zaac.19976230723
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  • 8
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    Thermodynamics and structure of molecular clusters in supercritical water (2000)
    In:  14th Symposium on Thermophysical Properties (Boulder 2000)
    Details
    Publikationsdatum: 2020-02-12
    Schlagwort(e): 550 - Earth sciences
    Materialart: info:eu-repo/semantics/conferenceObject
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  • 9
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    Thermodynamic of fluid mixtures at high temperature and pressures (2001)
    In:  European Union of Geosciences (EUG) XI (Strasbourg 2001)
    Details
    Publikationsdatum: 2020-02-12
    Schlagwort(e): 550 - Earth sciences
    Materialart: info:eu-repo/semantics/conferenceObject
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  • 10
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    Ab-initio calculations of the proton location in topaz-OH, Al2SiO4(OH)2 (2004)
    In:  Physics and Chemistry of Minerals
    Details
    Publikationsdatum: 2020-02-12
    Beschreibung: The position of hydrogen in the structure of topaz-OH was determined by means of ab-initio quantum-mechanic calculations. Static lattice energy calculations predict the existence of four non-equivalent positions of protons, which are characterized by O4–H1... O1, O4–H2... O2, O4–H3... O3 and O4–H4... O4 hydrogen bonds. The distribution of the protons between positions of local equilibrium is controlled by the proton–proton avoidance rule and the strength of the hydrogen bonds. The most favourable configuration of hydrogen atoms is achieved for adjacent protons, which form O4–H3... O3 and O4–H4... O4 hydrogen bonds, respectively. The thermal excitation of atoms at a temperature of 55 K is large enough for the hydrogen atoms occasionally to change their positions to form O4–H1... O1 and O4–H2... O2 bonds. At ambient pressures and higher temperatures the protons are in a dynamic exchange between the allowed positions of local minima. As a consequence, for nearly room-temperature conditions, the dynamic change between different structural configurations leads to the violation of all possible symmetry elements and with that to space group #E5/E5#1. The flipping of the protons between different sites is achieved by simple rotation of the OH-dipole and does not produce any significant distortion of the framework of topaz, whose symmetry remains that of the space group Pbnm. Therefore, no reduction of symmetry has been observed in former X-ray studies on topaz-OH. Calculated IR absorption spectra of topaz-OH were found to be in good agreement with measured spectra. According to the calculations, the two favourable configurations of protons might correspond to the measured peak splitting within the OH-stretching range. An experimentally observed low-frequency band at 3520 cm–1 was assigned to the OH-stretching of the O4–H3... O3 bond, while the band at 3600 cm–1 was attributed to OH-stretching of the O4–H4... O4 hydrogen bond. The broad peak in FAR-IR frequency range at 100–150 cm–1 is attributed to the stretching of H3... O3 and H4... O4 contacts. The rate of proton exchange at 670 K among different sites was estimated by ab-inito molecular dynamic simulations. The calculations predict that flipping of adjacent protons between O4–H3... O3 and O4–H4... O4 bonds at 670 K occur at a rate of about 1.96 THz.
    Schlagwort(e): 550 - Earth sciences
    Materialart: info:eu-repo/semantics/article
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