ISSN:
0538-8066
Keywords:
Chemistry
;
Physical Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The thermal unimolecular decomposition of ethylbenzene, isopropylbenzene, and tert-butylbenzene was studied using the very-low-pressure pyrolysis (VLPP) technique. Each reactant decomposed by way of β C—C bond homolysis, producing methyl radicals and benzyl or benzylic-type radicals. RRKM calculations show that the observed rate constants, when combined with thermochemical estimates, are consistent with the following high-pressure rate expressions: \documentclass{article}\pagestyle{empty}\begin{document}$ \log k(\sec ^{ - 1}) = 15.3 - (72.7/{\rm \theta)} $\end{document} for ethylbenzene between 1053 and 1234 K, \documentclass{article}\pagestyle{empty}\begin{document}$ \log k(\sec ^{ - 1}) = 15.8 - (71.3/{\rm \theta)} $\end{document} for isopropylbenzene between 971 and 1151 K, and \documentclass{article}\pagestyle{empty}\begin{document}$ \log k(\sec ^{ - 1}) = 15.9 - (69.1/{\rm \theta)} $\end{document} for tert-butylbenzene between 929 and 1157 K, where θ (kcal/mol) = 2.303RT. Resulting activation energies combined with heat capacity and heat of formation data led to the following dissociation enthalpies and enthalpies of formation at 298 K: DH° (øCH(CH3)—CH3) = 73.8 kcal/mol, ΔHf° (øÇCH(CH3)) = 39.6 kcal/mol, DH° (øC(CH3)2—CH3) = 72.9 kcal/mol, and ΔHf° (øÇ(CH3)2) = 32.4 kcal/mol. Derived high-pressure rate constants are in good accord with results of lower temperature toluene- and aniline-carrier experiments.
Additional Material:
5 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/kin.550130503
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