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  • Inorganic Chemistry  (376)
  • Physical Chemistry  (168)
  • Wiley-Blackwell  (544)
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  • 1
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Mixtures of 1,1,3,3-tetrafluoroacetone and perfluorodi-n-propyl ketone have been photolyzed together over the temperature range 50° to 200°C, and the disproportionation/combination ratio for n-C3F7 and CF2H radicals has been determined to be Δ(n-C3F7, CF2H) = 0.072 ± 0.003. A reevaluation of existing data on CH3 and CF2H radicals leads to a value of Δ(CH3, CF2H) = 0.35. The large variations in Δ for the reactions of alkyl and perfluoroalkyl radicals with CF2H radicals are discussed. © John Wiley & Sons, Inc.
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  • 2
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A redetermination of the disproportionation/combination ratio for n-C3F7 and C2H5 radicals gives a value of Δ(n-C3F7, C2H5) = 0.13 ± 0.01, independent of the temperature. The radicals were produced by the photolysis of n-C3F7COC2H5. The previous determinations of this ratio are discussed and are found to be largely incorrect. The values for Δ(CF3, C2H5) and Δ(C2F5, C2H5) are also re-evaluated, and the recommended values are 0.10 ± 0.02 and 0.12 ± 0.02, respectively. Systems involving perfluoroalkyl and ethyl radicals are complicated due to rapid perfluororadical addition to the ethylene formed in the disproportionation process. The extent of this reaction, and its consequences, are discussed and evaluated. The role of the propionyl (C2H5CO) radical in the room temperature photolysis is also assessed. However, it is found that the Δ values determined by the intercept method used in this work are not affected by the secondary reactions that occur. It is concluded that high cross-combination ratios are general to perfluoroalkyl-alkyl radical interactions. For C3F7 and C2H5 radicals the ratio is 2.7-2.8. Above 100°C ratios exceed 3 due to secondary reactions.
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 23 (1991), S. 103-103 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 2513-2517 
    ISSN: 0009-2940
    Keywords: Dibenzo [CH]8 hydrocarbons ; Flow-vacuum pyrolysis ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The flow-vacuum pyrolysis of dibenzo [CH]8 hydrocarbons 2,3,4, and 5 are studied at 1 Torr and in the temperature range between 400 and 650°C. The following new transformations have been observed: 2⇆4, 2→5, 3→5, 3⇆4, 3→2, 5→11, the last three presenting analogies in the [CH]8 and/or benzo [CH]8 series. A reaction mechanism is suggested.
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  • 5
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 6
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The title compounds (1 and 3, respectively) were studied by X-ray crystal structure analysis. Both are trigonal, space group R3, with lattice parameters a = 27.718(6), c = 8.161(2) Å, Z = 3 and a = 31.267(7), c = 6.560(2), Z = 18, respectively. The dodecamethyl compound 1 is isomorphous with its parent hexakis(4-benzylphenoxy)benzene (2), a known host. However, ‘collapse’ along the c-axial direction has occurred such that the appreciable clathrate cavity of 2 has been replaced by only a very small residual void for 1. Phenol 3 does not pack in discrete [OH]6 hydrogenbonded hexamers; instead, molecules are assembled in infinite chains, linked by OH…O hydrogen bonds of length 2.735(3) Å, which are propagated along threefold screw axes. A variable-temperature CPMAS NMR study of sidechain aryl group rotation in 1 gives a value ΔG≠ of 14.0 ± 0.7 kcal mol-1 (at 42 °C) for the (crystallographically unique) para -disubstituted ring, a similar 14 kcal mol-1 free energy barrier being found hindering rotation of this ring, and of the outer phenyl ring of 1, at 9°C.
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  • 7
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: It has been established that the product of the reaction of N-pentafluorophenylcarbonimidoyl dichloride (1) with dibenzylamine, viz. N2-pentafluorophenyl-N1,N1-dibenzylchloroformamidine (4a) is a Z-isomer, whereas according to the concept of stereoelectronic control one might have expected a product with E-configuration. The heat of formation and the geometry of Z- and E isomer of N2-pentafluorophenyl-N1,N1-diethylchloroformamidine (4b) (the latter is a product of the reaction of 1 with diethylamine) were calculated with the semi-empirical MNDO method. The calculated geometry of (Z)-4b was found to be in a good agreement with the experimentally determined structure of 4a. The formation of (Z)-4b is more preferable energetically than that of (E)-4b; the calculated difference in the heats of formation is 2·8 kcal mol-1. Thermodynamic control of the reaction stereochemistry is proposed.
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  • 8
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 620 (1994), S. 1976-1982 
    ISSN: 0044-2313
    Keywords: Gas complex ; MnAlF5 ; mass spectroscopy ; enthalpie of dissociation ; ab initio calculation ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: The Gas Complex MnAlF5 and its Influence on the Purification of AlF3 by SublimationThe gas complex MnAlF5 has been determined mass spectroscopically by the ions MnAlF5+ and MnAlF4+. The gas complex MnAlF5 is formed above 973 K by heating up mixtures of AlF3/MnF2 or AlF3 · 3 H2O endowed with Mn2+ or by heating up solid MnAlF5 too. At 1 008 K the enthalpie of dissociation is 197 kJ/mole. The equilibrium structures of the high spin molecule MnAlF5 (S = 5/2) were examined with ab initio calculations at the HF-level by comlete gradient optimizing. Two minimum structures were found on the potential energy surface. A bidentate fluorine bridged structure was found to be the most stable at the HF-level. Vibrational frequencies and thermodynamic functions of complex formation were estimated for both minimum structures. The importance of the formation of the gas complex for the separation of MnF2 and AlF3 by sublimation is discussed.
    Notes: Der Gaskomplex MnAlF5 wurde bei massenspektrometrischen Untersuchungen durch die Ionen MnAlF5+ und MnAlF4+ nachgewiesen; er bildet sich beim Aufheizen von AlF3/MnF2-Gemengen, Mn-dotiertem AlF3 · 3 H2O bzw. festem MnAlF5 oberhalb 973 K. Die experimentell ermittelte Dissoziationsenthalpie bei 1 008 K für den Zerfall MnAlF5(g) = MnF2(g) + AlF3(g) beträgt 197 kJ/mol. Die Gleichgewichtsstrukturen von MnAlF5(g) (high spin; S = 5/2) wurden durch ab initio Berechnungen auf HF-Niveau durch vollständige Gradientenoptimierung ermittelt. Zwei Minimumstrukturen wurden gefunden. Eine zweifach F-verbrückte Ringstruktur ist auf HF-Niveau die stabilste. Schwingungsfrequenzen und thermodynamische Komplexbildungsfunktionen werden für beide Minimumstrukturen angegeben. Die Bedeutung des Gaskomplexes für die sublimative Trennung von MnF2 und AlF3 wird diskutiert.
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  • 9
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 592 (1991), S. 207-216 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Preparation and 29Si NMR Spectroscopic Investigation of Polymers with Definite Silicic Acid UnitsThree polymers were synthesized by additive reaction of the cage-like double fourring (D4R) silicic acid derivatives [(CH3)2HSi]8Si8O20 and [CH2=CH(CH3)2Si]8Si8O20 resp., with the unsaturated diviyltetramethyldisiloxane or the multiple functional tetramethylcyclotetrasiloxane and polymethylhydrogensiloxane in a molar ratio of functional groups 1:1. By means of 29Si solid state NMR spectroscopy was shown that the in organic solvents insoluble polymers are built up by D4R silicic acid units, which are connected by chain-like or cyclic siloxane bridges. With increasing functional groups of the reactants the sterical hindrance of the reaction of D4R derivates grows. The polymers show small surfaces of 1 to 8 m2/g.
    Notes: Durch Additionsreaktion der käfigartigen Doppelvierring-(D4R-)kieselsäurederivate [(CH3)2Hsi]Si8O20 mit dem zweifach ungesättigten Divinyltetramethyldisiloxan bzw. den mehrfachfunktionellen Tetramethylcyclotetrasiloxan und Polymethylhydrogensiloxan in molaren Verhältnis der funktionellen Gruppen von 1:1 wurden 3 in organischen Lösungsmitteln unlösliche Polymere hergestellt. 29Si-Festkörper-NMR-Untersuichungen zeigen, daß sich die Polymere aus D4R-Kieselsäureeinheiten aufbauen, die über ketten- oder ringförmige Siloxanbrückcn miteinander vernetzt sind. Mit zunehmender Zabl funktioneller Gruppen in den Reaktionspartnern der D4R-Derivate wächst die räumliche Behinderung der Vernetzungsreaktionen. Die Polymere weisen nur eine kleine Oberfläche zwischen 1 und 8 m2/g auf.
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  • 10
    ISSN: 0044-2313
    Keywords: Nickel(II), cobalt(II) phosphinothioic-N-organylamidato chelates ; magnetism ; crystal structures ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Nickel(II) and Cobalt(II) Phosphinothioic-N-Organylamidato Chelates [R2P(S)NR′]2M: Magnetic Properties and Crystal StructuresPhosphinothioic-N-organylamidato chelates [R2P(S)NR′]2M (R, R′ = organyl; M = Ni, Co) 1, 2 have been obtained by reaction of MCl2 with [R2P(S)NR′]Li. According to magnetic and spectroscopic measurements (UV/VIS) NiII complexes 1 d (R = i-Pr, R′ = Me), 1 h (R = t-Bu, R′ = Me), 1 i (R = t-Bu, R′ = Et) and 1 m (R = t-Bu, R′ = Ph) are planar in solid state. For 1 i transgeometry of the donor atoms in the chromophore NiN2S2 has been proved. NiII complexes 1 a (R = Me, R′ = i-Pr) and 1 b (R = Me, R′ = c-Hex) show magnetic moments of c. 1.2 B.M. Magnetic moments of all other solid complexes 1, 2 are in a range usually found with tetrahedral coordination. In solution 1 c (R = Me, R′ = t-Bu), 1 e-g (R = i-Pr; R′ = i-Pr, c-Hex, t-Bu), and 1 j-l (R = t-Bu; R′ = i-Pr, c-Hex, t-Bu) are entirely tetrahedral while with 1 a, 1b, 1 i, and 1 m there exists an equilibrium planar ⇌ tetrahedral. This is shifted to the right with increasing R and R′ the influence of R being less than that of R′. The crystal structures of 1 k (R = t-Bu, R′ = c-Hex) and 2 a (R, R′ = t-Bu) reveal a distorted tetrahedral coordination. 1 k: orthorhombic, a = 1 343.7(1), b = 1 514.9(1), c = 1 632.4(2) pm; Pccn, Z = 4, 3 205 reflections, R = 0.03. 2 a: orthorhombic, a = 1 637.9(2), b = 2 997.0(3), c = 1 282.4(1) pm; Pbca, Z = 8, 4 742 reflections, R = 0.04.
    Notes: Durch Umsetzung von MCl2 mit [R2P(S)NR ′]Li wurden die Thiophosphinsäureamidato-Chelate [R2P(S)NR ′]2M (R, R′ = Organyl; M = Ni, Co) 1, 2 erhalten. Magnetischen und spektroskopischen Messungen (UV/VIS) zufolge sind die NiII-Komplexe 1 d (R = i-Pr, R′ = Me), 1 h (R = t-Bu, R′ = Me), 1i (R = t-Bu, R′ = Et) und 1m (R = t-Bu, R′ = Ph) im Festkörper planar, wobei für 1i trans-Stellung der Donatoratome im Chromophor NiN2S2 nachgewiesen wurde. Im Festzustand weisen die NiII-Komplexe 1a (R = Me, R′ = i-Pr) und 1 b (R = Me, R′ = c-Hex) magnetische Momente von ca. 1,2 B.M. auf, während die aller anderen Komplexe 1, 2 in einem Bereich liegen, wie man ihn bei tetraedrischer Koordination erwartet. In Lösung erweisen sich 1 c (R = Me, R′ = t-Bu), 1 e-g (R = i-Pr; R′ = i-Pr, c-Hex, t-Bu) und 1 j-l (R = t-Bu; R′ = i-Pr, c-Hex, t-Bu) als rein tetraedrisch, während 1 a, 1 b, 1 i und 1 m einem Konformerengleichgewicht planar ⇌ tetraedrisch unterliegen, das sich mit steigender Raumerfüllung von R und R′ nach rechts verschiebt. Der Einfluß von R ist hierbei geringer als der von R′. Kristallstrukturanalysen für 1 k (R = t-Bu, R′ = c-Hex) und 2 a (R, R′ = t-Bu) bestätigen eine verzerrt tetraedrische Koordination. 1 k: rhombisch, a = 1 343,7(1), b = 1 514,9(1), c = 1 632,4(2) pm; Pccn, Z = 4; 3 205 Reflexe, R = 0,03. 2 a: rhombisch, a = 1 637,9(2), b = 2 997,0(3), c = 1 282,4(1) pm; Pbca, Z = 8; 4 742 Reflexe, R = 0,04.
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