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  • 1
    ISSN: 1040-0397
    Keywords: Calix[4]arene ; Partial cone conformation ; Ionophore ; Silver-selective electrode ; Potentiometry ; PVC membrane ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two calix[4]arene derivatives, in the partial cone conformation, with sulfur-containing functionalities, were tested as neutral carrier ionophores in potentiometric silver-selective electrodes of conventional membrane and membrane-coated glassy carbon electrode types. Comparison with a calix[4]arene in the cone conformation was made. The membranes were prepared using either 2-nitrophenyl octyl ether or bis(ethylhexyl)sebacate as plasticizers and potassium tetrakis(p-chlorophenyl)borate as the lipophilic salt in a poly(vinyl chloride) matrix. Both calix[4]arenes yielded electrodes of good sensitivity (approx. 47 mV dec-1) in the range 10-4-10-1 M and excellent selectivity [log KAg,MH+ 〈 -1.5] of transition, alkali and heavy metal cations, including sodium, mercury(II) and lead(II) cations. Temperature effects and reproducibility of response were determined and the interfering effects of mercury(II) and lead (II) ions on the membranes were noted. The partial cone conformation allows improved selectivity over certain cations relative to calix[4]arenes in the cone conformation.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 20 (1988), S. 939-955 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A flow system has been developed to study relative rate coefficients of hydroxyl radicals reacting with alkanes under conditions relating to tropospheric chemistry. Relative Arrhenius parameters have been measured over the temperature range 243-328 K for pairs of alkanes from a list consisting of n-butane, 2-methylpropane, n-pentane, n-hexane, 2,2- and 2,3-dimethylbutane, 2,3,3-trimethylbutane, and 2,3,4-trimethylpentane.The results have been incorporated into a Structure-Activity Relation for hydroxylalkane reactions which leads to the following group rate coefficients for a temperature range of 240-500 K. \documentclass{article}\pagestyle{empty}\begin{document}$$\begin{array}{rcl} k_{{\rm prime}}^0 &=& 3.13 \times 10^{ - 12}\, {\rm exp(} - 904/T)\,{\rm cm}^{\rm 3}\, {\rm molecule}^{ - 1}\, {\rm s}^{ - 1} \\ k_{{\rm sec}}^0 &=& 2.45 \times 10^{ - 12} \,{\rm exp(} - 320/T)\,{\rm cm}^{\rm 3}\, {\rm molecule}^{ - 1}\, {\rm s}^{ - 1} \\ k_{{\rm tert}}^0 &=& 1.88 \times 10^{ - 12} \,{\rm cm}^{\rm 3}\, {\rm molecule}^{ - 1}\, {\rm s}^{ - 1} \end{array}$$\end{document}
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 21 (1989), S. 207-218 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The photo-oxidation of n-heptane in synthetic air containing methyl nitrite and nitric oxide has been ivestigated in an atmospheric flow reactor. By measuring the total yields of heptyl nitrate products, relative to the depletion of the n-heptane, the rate constant ratio, k3b/k3a has been determined for the reactions: Over the temperature range 253-325 K and at a total pressure of 730 Torr, the following relative Arrhenius equation has been obtained from the present study together with literature data: \documentclass{article}\pagestyle{empty}\begin{document}$$k_{3b} /k_{3a} = (1.4 \pm 1.1) \times 10^{ - 3} \exp [1640 \pm 250)/T]$$\end{document} These results confirm that the formation of alkyl nitrates from the photo-oxidation of n-alkanes arise from a primary reaction between the alkylperoxy radicals and nitric oxide. Furthermore the present experiments show that the lifetime of the intermediate in this type of reaction, presumed to be an alkyl peroxynitrite, ROONO, must be less than a few seconds.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 19 (1987), S. 609-614 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The rates of decay of ozone in a large excess of the cycloalkene have been re-measured by an improved experimental procedure, and the following second-order rate constants (cm3 molecule-1 s-1) have been determined in synthetic air at atmospheric pressure: \documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{*{20}c} {{\rm O}_3 + {\rm cyclopentene} \longrightarrow {\rm products,}} & {k = (4.97 \pm 0.30) \times 10^{ - 16} {\rm at}} \\ \end{array}291.5{\rm K} $$\end{document} \documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{*{20}c} {{\rm O}_3 + {\rm cyclohexene} \longrightarrow {\rm products,}} & {k = (1.51 \pm 0.10) \times 10^{ - 16} {\rm at}} \\ \end{array}295{\rm K} $$\end{document} The results are discussed in relation to existing literature data on the kinetics of ozonecycloalkene reactions.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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