Reactivity of C2H5+ with benzene: formation of ethylbenzenium ions and implications for Titan's ionospheric chemistry.
The reaction of ethyl cation with benzene has been investigated in a combined experimental and theoretical approach. Under single collision conditions, proton transfer affording protonated benzene concomitant with neutral ethene represents the major reaction channel. From pressure-dependent measurements, an absolute cross section of 7 +/- 2 A(2) at hyperthermal energies (about 1.0 eV in the center of mass frame) is derived for this channel, from which a phenomenological rate constant of about 2.9 x 10(-10) cm(3) s(-1) is estimated at low energies. The energy behavior of the cross section as well as several side reactions leading to C-C coupling imply that the reaction of C(2)H(5)(+) with C(6)H(6) proceeds via a long-lived association product, presumably the covalently bound protonated ethylbenzene (ethylbenzenium ion). With regard to chemical processes in the atmosphere of Titan, present results imply that termolecular association of C(2)H(5)(+) with benzene to produce protonated ethylbenzene is very likely to occur. The condensation of alkyl cations with arenes thus provides an alternative route for the growth of larger hydrocarbon molecules.
Zabka
Jan
J
J Heyrovský Institute of Physical Chemistry, V Cermák Laboratory, Academy of Sciences of the Czech Republic, 18223 Prague 8, Czech Republic.
Polásek
Miroslav
M
Ascenzi
Daniela
D
Tosi
Paolo
P
Roithová
Jana
J
Schröder
Detlef
D