Isomerization and dissociation of n-butylbenzene radical cation.

Abstract : Fragmentation mechanisms of ionized butylbenzene to give m/z 91 and m/z 92 fragment ions have been examined at the G3B3 and G3MP2B3 levels of theory. It is shown that the energetically favored pathways lead to tropylium, Tr(+), and methylene-2,4-cyclohexadiene, MCD(*+), ions. Formation of m/z 91 benzyl ions, Bz(+), by a simple bond fission (SBF) process, needs about 30 kJ/mol more energy than Tr(+). Possible formation of C(7)H(8)(*+) ions of structures different from the retro-ene rearrangement (RER) product, MCD(*+), has been also considered. Comparison with experimental data of this "thermometer" system is done through a kinetic modeling using Rice-Ramsperger-Kassel-Marcus (RRKM) and orbiting transition state (OTS) rate constant calculations on the G3MP2B3 0 K energy surface. The results agree with previous experimental observation if (i) the competitive formation of Tr(+) and Bz(+) is taken into account in the m/z 91 pathway, and (ii) the stepwise character of the RER fragmentation is introduced in the m/z 92 fragmentation route.
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Submitted on : Friday, November 29, 2013 - 2:35:32 PM
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Stephanie Halbert, Guy Bouchoux. Isomerization and dissociation of n-butylbenzene radical cation.. Journal of Physical Chemistry A, American Chemical Society, 2012, 116 (4), pp.1307-1315. ⟨10.1021/jp211673f⟩. ⟨hal-00904400⟩

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