Reference : Kinetic Energy Release Distributions for Tropylium and Benzylium Ion Formation from t...
Scientific journals : Article
Physical, chemical, mathematical & earth Sciences : Chemistry
Kinetic Energy Release Distributions for Tropylium and Benzylium Ion Formation from the Toluene Cation.
[fr] Distribution de l'énergie cinétique emportée lors de la formation des ions tropylium et benzylium à partir du cation du toluène.
Fati, D. [> > > >]
Lorquet, Andrée mailto [Université de Liège - ULiège > Département de chimie (sciences) > Laboratoire de dynamique moléculaire >]
Locht, Robert mailto [Université de Liège - ULiège > Département de Chimie (Faculté des Sciences) > Laboratoire de Dynamique Moléculaire (Sciences) >]
Lorquet, Jean-Claude mailto [Université de Liège - ULiège > Département de Chimie (Faculté des sciences) > Laboratoire de Dynamique Moléculaire (Sciences) > >]
Leyh, Bernard mailto [Université de Liège - ULiège > Département de chimie (sciences) > Laboratoire de dynamique moléculaire >]
Journal of Physical Chemistry A
Amer Chemical Soc
Tomas Baer Festschrift
Yes (verified by ORBi)
[en] Kinetic energy release distributions ; Metastable time window ; Maximum entropy method ; Orbiting Transition State Theory (OTST) ; Tropylium+/Benzylium+ ; Toluene ; Reverse electronic activation barrier
[en] Hydrogen loss from the toluene molecular ion generates benzylium (Bz(+)) and tropylium (Tr+) ions via two competitive and independent pathways. The corresponding kinetic energy release distributions (KERDs) have been determined under various conditions in the metastable time window for toluene and perdeuterated toluene and have been analyzed by the maximum entropy method (MEM). The isomeric fraction Tr+/Bz(+) is found to be equal to 0.9 +/- 0.3, in good agreement with the values obtained using photodissociation and charge exchange experiments. It is, however, in disagreement with the value 5 +/- 2 deduced by Moon, Choe, and Kim (J. Phys. Cheln. A 2000, 104, 458) from KERD measurements. The origin of the discrepancy is suggested to be the inadequacy of the orbiting transition state theory (OTST) for the calculation of KERDs in hydrogen loss reactions. For both channels, more translational energy is released in the reaction coordinate than would be expected on statistical grounds because of the presence of a barrier along the reaction path. For the Bz(+) channel, the barrier entirely results from centrifugal effects. Rotational energy is converted into translation as a result of angular momentum conservation. Deuteration is observed to reduce the importance of the rotational energy flow in the reaction coordinate. The Tr+ channel is characterized by the presence of a reverse activation energy barrier of electronic origin. The energy in excess of the dissociation asymptote can be partitioned into two components: the reverse barrier plus a nonfixed energy contribution. About 40% of the reverse barrier is converted into relative translational motion of the fragments. Here again, a lower fraction of the nonfixed energy flows into translation for the deuterated isotopomer.
Laboratoire de Dynamique Moléculaire
Fonds de la Recherche Scientifique (Communauté française de Belgique) - FNRS, ARC Contract n° 99-04/245
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