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  • Articles: DFG German National Licenses  (190)
  • 1995-1999  (133)
  • 1970-1974  (57)
  • Physical Chemistry  (190)
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  • Articles: DFG German National Licenses  (190)
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  • 1
    Electronic Resource
    Electronic Resource
    Kinetics and mechanism of the reaction of Cl atoms with CH2 CO (Ketene) (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 28 (1996), S. 627-635 
    Details
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics and mechanism of the gas-phase reaction of Cl atoms with CH2CO have been studied with a FTIR spectrometer/smog chamber apparatus. Using relative rate methods the rate of reaction of Cl atoms with ketene was found to be independent of total pressure over the range 1-700 torr of air diluent with a rate constant of (2.7 ± 0.5) × 10-10 cm3 molecule-1 s-1 at 295 K. The reaction proceeds via an addition mechanism to give a chloroacetyl radical (CH2ClCO) which has a high degree of internal excitation and undergoes rapid unimolecular decomposition to give a CH2Cl radical and CO. Chloroacetyl radicals were also produced by the reaction of Cl atoms with CH2ClCHO; no decomposition was observed in this case. The rates of addition reactions are usually pressure dependent with the rate increasing with pressure reflecting increased collisional stabilization of the adduct. The absence of such behavior in the reaction of Cl atoms with CH2CO combined with the fact that the reaction rate is close to the gas kinetic limit is attributed to preferential decomposition of excited CH2ClCO radicals to CH2Cl radicals and CO as products as opposed to decomposition to reform the reactants. As part of this work ab initio quantum mechanical calculations (MP2/6-31G(d,p)) were used to derive ΔfH298(CH2ClCO) = -(5.4 ± 4.0) kcal mol-1. © 1996 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/kin.8
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    The pyrolysis of neopentane at small extents of reaction (1971)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 3 (1971), S. 197-213 
    Details
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The pyrolysis of neopentane, at small extents of reaction, was studied by gas chromatography, in Pyrex reaction vessels between 450° and 530°C and in the initial pressure range 25-200 mm Hg. At initial time, this thermal decomposition can be essentially represented by a homogeneous long-chain radical mechanism. The rate constant of the unimolecular initiation process is approximately given by the expression \documentclass{article}\pagestyle{empty}\begin{document}$$k_{\rm 0} \simeq 10^{13} {\rm exp}\left({\frac{{50,000}}{{RT}}} \right){\rm mole}^{- {\rm 1/2}} {\rm .ml}^{- {\rm 1/2}} {\rm .s}^{- {\rm 1}}$$\end{document} The initial rate constant of the global reaction (order 3/2) is nearly equal to \documentclass{article}\pagestyle{empty}\begin{document}$$k_{\rm 1} + 10^{16.8} {\rm exp}\left({\frac{{82,000}}{{RT}}} \right){\rm s}^{- {\rm 1}}$$\end{document} This reaction is strongly inhibited by propene or isobutene and self-inhibited by the isobutene formed; an interpretation of all these inhibition phenomena of the neopentane pyrolysis is proposed. Our observations and conclusions, which have been summarized in communications during 1968 and 1969, are compared to those of other authors, particularly to the recent ones of Purnell and colleagues [13] and of Taylor and colleagues [14], [15].
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/kin.550030302
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  • 3
    Electronic Resource
    Electronic Resource
    A diode laser study of the Cl + CH3CO reaction (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 29 (1997), S. 421-429 
    Details
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Real-time kinetic measurements are reported for the Cl + CH3CO → CH2CO + HCl reaction. The experiments utilize infrared spectroscopy to determine the time dependence of the ketene formed via this reaction and of the CO produced from the subsequent rapid reaction between chlorine atoms and ketene. The reaction is investigated over a pressure range of 10-200 torr and a temperature range of 215-353 K. Within experimental error the rate constant under these conditions is k5a = (1.8 ± 0.5) × 10-10 cm3 s-1. We have also examined the Cl + CH2CO reaction and found it to have a rate constant of k6 = (2.5 ± 0.5) × 10-10 cm3 s-1 independent of temperature. © John Wiley & Sons, Inc. Int J Chem Kinet 29: 421-429, 1997.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 4
    Electronic Resource
    Electronic Resource
    Kinetics of oxidation of indigo carmine by N-sodio-N-bromotoluenesulfonamide in acidic buffer medium (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 29 (1997), S. 453-459 
    Details
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics of oxidation of indigo carmine (IC) by N-sodio-N-bromotoluenesulfonamide or bromamine-T (BAT) in pH 5 buffer medium has been investigated at 30°C using spectrophotometry at 610 nm. The reaction rate shows dependencies of first-order on [IC]0 second-order on [BAT]0, fractional order on [H+], and inverse first-order on [ρ-toluenesulfonamide]. The addition of chloride and bromide ions, and the variation of ionic strength of the medium have no influence on the reaction rate. There is a negative effect of the dielectric constant of the solvent. Activation parameters have been calculated. A single-pathway mechanism for the reaction, consistent with the kinetic data, has been proposed. © John Wiley & Sons, Inc. Int J Chem Kinet 29: 453-459, 1997
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 5
    Electronic Resource
    Electronic Resource
    Aquation kinetics of chloropentamminecobalt (III) perchlorate in dicarboxylate media containing 10% (v/v) acetone (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 29 (1997), S. 311-316 
    Details
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The aquation kinetics of [Co(NH3)5Cl]2+ in dicarboxylate media containing 10% (v/v) acetone is measured in the temperature range of 35-60°C. A new empirical correlation between the rate coefficient, kobs, and the stoichiometric concentration of the dicarboxylate ligand (CL) has been established and a reaction mechanism is proposed. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 311-316, 1997.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 6
    Electronic Resource
    Electronic Resource
    Interrelations Of the energetics of amides and alkenes: Enthalpies of formation of N,N-dimethyl derivatives of pivalamide, 1-adamantylcarboxamide and benzamide, and of styrene and its α-, trans-β- and β,β-methylated derivatives (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 15-25 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The enthalpies of formation of the condensed phase and gaseous N,N-dimethyl derivatives of pivalamide, 1-adamantylcarboxamide and benzamide were determined by combustion calorimetry and the associated enthalpies of vaporization and sublimation. The enthalpies of formation of styrene and its α-, trans-β- and β,β-methylated derivatives were determined from measurements of their enthalpies of hydrogenation in dilute hydrocarbon solution. Strain and resonance effects of amides and alkenes are discussed in terms of the exo-/endothermicity of the following reactions: and in terms of the difference of enthalpies of formation of the isomeric (Z)- and E-RCH=CHCH3.
    Additional Material: 6 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610080105
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  • 7
    Electronic Resource
    Electronic Resource
    Reaction of phenoxy radical with nitric oxide (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 47-53 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The associationof C6H5O with NO was studied with the cavity-ring-down method by directly monitoring the decay of C6H5O in the presence of varying, excess amounts of NO. The biomolecular rate constant determined in the temperature range 297-373 K can be effectively rate constant determined in the temperature range 297-373 K can be effectively represented by k1 = 10- 12 · 12 ± 0.24e (194±185)/r cm3 molecule-1 with a negative activation energy of 0.8 kcal mol-1 (1 kcal = 4.184 kJ). In order to understand better the mechanism of the reaction, ab initio molecular orbital calculations were also carried out at the MP4(SDQ)/6-31G* level of theory using the HF optimized geometries. The molecular structues and energetics of five C6H5N1O2 isomers were calculated. Among them, the most likely and stable association product, phenyl nitrite (C4H5ONO), was found to be 17 kal mol-1 below the reactants, C6H5O + NO. Combining the measured rate constant and the calculated equilibrium constant for the association reaction, C6H5O + NO = C6H5ONO the rate constant for the unimolecular decomposition of C6H5ONO was obtained as k-1 = 4.6 × 1015E-8580/T s-1. The relatively large frequency factor suggests that a loose transition state was involved in the reaction, akin to those of its alkyl analogs (RONO, R = CH3, C2H5, etc.).
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610080110
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  • 8
    Electronic Resource
    Electronic Resource
    Enthalpies of micelle formation by hexadecyltrimethylammonium bromide in aqueous solution containing pentanol (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 108-112 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Titration calorimetric data show a dramatic change from endo- to exothermic deaggregation when pentanol-hexadecyltrimethylammonium bromide (CTAB) mixed solutions are injected into an aqueous solution containing pentanol. The results are interpreted in terms of a change in the structures of the aggregates in solution from simple CTAB micelles to mixed amphiphilic microheterogeneities when pentanol is added.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610080210
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  • 9
    Electronic Resource
    Electronic Resource
    Structure of the intermediate formed in the synthesis of symmetrical pyrylium ions (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 731-741 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The synthesis of symmetrical blocked pyrylium derivatives by reaction of a cyclic aromatic ketone with ethyl orthoformate goes through an intermediate which can be isolated under certain conditions. This intermediate is unstable when starting from 1-tetralone derivatives but, surprisingly, it can be isolated easily when the synthesis is performed with 1-indanone derivatives. Further, in the latter case, this intermediate cyclizes hardly into the expected blocked pyrylium derivative. Its ionic structure was demonstrated by mass spectrometry and by 500 MHz 1H and 13C NMR techniques including heteronuclear H-C COSY and DEPT polarization transfer experiments. Hydrolysis of this intermediate in aqueous ethanol solution forms, in acidic or basic media, a pseudo-base, which in the latter case presents strong similarities with that obtained by the base-catalysed ring-opening of a blocked pyrylium ion. In both acidic and basic solutions, the pseudo-base obtained by the two sources shows identical UV-visible absorption spectra. The difficulty of the intermediate (g) originating from 1-indanone derivatives in cyclizing into the blocked pyrylium structure, in contrast to the intermediate formed from 1-tetralone derivatives, is tentatively explained.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610081106
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  • 10
    Electronic Resource
    Electronic Resource
    Determination of the empirical polarity parameter ET(30) for binary solvent mixturesSee Ref. 1. (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 617-625 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Empirical solvent polarity parameters ET(30) were determined by UV-visible spectrophotometry using Dimroth- Reichardt's betaine dye, as a function of composition, for (aprotic + aprotic) and (aprotic + protic) binary solvent mixtures. For (aprotic + aprotic) solvent systems the cosolvent was toluene, and the other solvents used were selected with different structural characteristics and an extensive range of polarity: chloroform, 1,4-dioxane, ethyl acetate, tetrahydrofuran, acetone, nitromethane and N,N-dimethylformamide. For (aprotic + protic) solvent systems, the protic cosolvent used was methanol, and the aprotic solvents selected were toluene, chloroform, 1,1,1-trichloroethane, tetrahydrofuran, acetone, N,N-dimethylformamide, and dimethyl sulphoxide. Each system was analysed according to its deviations from additivity due to selective solvation of the betaine. A preliminary application of these empirical solvent polarity parameters was related to the solvent effects in a simple example of a nucleophilic aromatic substitution reaction.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610080908
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