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  • Articles  (3)
  • Physical Chemistry  (3)
  • 1985-1989  (3)
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  • Articles  (3)
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  • 1
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The pyrolyses of cyanomethyl t-butyl sulfide and its oxygen homologue have been studied in a stirred-flow system over the temperature range 490-540°C and pressures between 5 and 14 Torr. In both cases, isobutene is formed as product in over 97% yield. Hydrogen sulfide is obtained in about half the amount of isobutene in the pyrolysis of the sulfide. Hydrogen cyanide is formed in the pyrolysis of the ether. The first-order rate coefficients for the consumption of the reactants followed the Arrhenius equations Cyanomethyl t-butyl sulfide: \documentclass{article}\pagestyle{empty}\begin{document}$$ k({\rm s}^{ - 1}) = 10^{12.63 \pm 0.23} \exp (- 201.7 \pm 3.5)\,{\rm kj}/{\rm mol }\,RT $$\end{document} Cyanomethyl t-butyl ether: \documentclass{article}\pagestyle{empty}\begin{document}$$ k({\rm s}^{ - 1}) = 10^{11.27 \pm 0.30} \exp (- 186 \pm 5)\,{\rm kj}/{\rm mol }\,RT $$\end{document}A molecular mechanism involving polar four-centered cyclic transition states is proposed for both reactions, with the CN group stabilizing the partial negative charge developed at the S and O atoms.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The pyrolysis kinetics of the title compounds has been studied in a stirred-flow reactor over the temperature range 440-530°C and pressures between 5 and 14 torr. Benzyl t-butyl sulfide and phenyl t-butyl ether formed isobutene as product in over 98% yield, together with the corresponding benzyl thiol and phenol. The benzyl thiol decomposes to a large extent into hydrogen sulfide and bibenzyl. In the pyrolysis of phenyl t-butyl sulfide, the hydrocarbon products consisted of 80 ±5% isobutene plus 20% isobutane, while the sulfur containing products were thiophenol and diphenyl disulfide. Order one kinetics was observed for the consumption of the reactants. The first order rate coefficients, based on isobutene production, followed the Arrhenius equations: Benzyl t-butyl sulfide: \documentclass{article}\pagestyle{empty}\begin{document}$$k(s^{ - 1}) = 10^{13.82 \pm 0.41} \exp ( - 214 \pm 6{\rm kJ/mol }RT)$$\end{document} Phenyl t-butyl sulfide: \documentclass{article}\pagestyle{empty}\begin{document}$$k(s^{ - 1}) = 10^{12.03 \pm 0.39} \exp ( - 188 \pm 6{\rm kJ/mol }RT)$$\end{document} Phenyl t-butyl ether: \documentclass{article}\pagestyle{empty}\begin{document}$$k(s^{ - 1}) = 10^{14.30 \pm 0.21} \exp ( - 211 \pm 3{\rm kJ/mol }RT)$$\end{document}For benzyl t-butyl sulfide and phenyl t-butyl ether, the results suggest a unimolecular mechanism involving polar four center cyclic transition states. For phenyl t-butyl sulfide, the t-butyl-sulfur single bond fission mechanism is a parallel, less important process than the complex fission one.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The pyrolyses of four alkyl allyl sulfides with substituents on the α—C atom of the alkyl moiety have been studied in a stirred-flow system over the temperature range 340-400°C and pressures between 2 and 12 torr. The only products formed are propene and thioaldehydes. The reactions showed first-order kinetics with the rate coefficients following the Arrhenius equations: Chloromethyl allyl sulfide: \documentclass{article}\pagestyle{empty}\begin{document}$$ k({\rm s}^{{\rm - 1}}) = 10^{10.74 \pm 0.23} \exp ( - 144 \pm 3){\rm kJ/mol}RT $$\end{document} Cyanomethyl allyl sulfide: \documentclass{article}\pagestyle{empty}\begin{document}$$ k({\rm s}^{{\rm - 1}}) = 10^{10.20 \pm 0.19} \exp ( - 129 \pm 2){\rm kJ/mol}RT $$\end{document} 1-cyanoethyl allyl sulfide: \documentclass{article}\pagestyle{empty}\begin{document}$$ k({\rm s}^{{\rm - 1}}) = 10^{11.09 \pm 0.18} \exp ( - 141.5 \pm 2.2){\rm kJ/mol}RT $$\end{document} Neopentyl allyl sulfide: \documentclass{article}\pagestyle{empty}\begin{document}$$ k({\rm s}^{{\rm - 1}}) = 10^{10.54 \pm 0.24} \exp ( - 144 \pm 3){\rm kJ/mol}RT $$\end{document}The effects of these and other substituents on the reactivity is discussed in relation with the stabilization of a polar six-centered transition state. The results support a non-concerted mechanism where the 1-5 α—H atom shift is assisted by its acidic character.
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
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