Reactivity of C₂H₅⁺ with Benzene: Formation of Ethylbenzenium Ions and Implications for Titan’s Ionospheric Chemistry

Abstract

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.

An empirical approach to modeling ion production rates in Titan's ionosphere I: Ion production rates on the dayside and globally

“…[] and Zabka et al . [] requires that the electron dissociative recombination rate coefficient for HCNH + be increased by at least a factor of 10 (if this is really the explanation for the high electron densities). The required increased loss rate could be due to processes leading from HCNH + and C 2 H 5 + to higher mass ion species, followed by increased recombination.…”

“…4. Using the chemical reaction pathways of Anicich and McEwan [1997], McEwan and Anicich [2007], and Vuitton et al [2006Vuitton et al [ , 2007 with updated reaction rate coefficients observed by Edwards et al [2008] and Zabka et al [2009] requires that the electron dissociative recombination rate coefficient for HCNH + be increased by at least a factor of 10 (if this is really the explanation for the high electron densities). The required increased loss rate could be due to processes leading from HCNH + and C 2 H 5 + to higher mass ion species, followed by increased recombination.…”

“…[] for CH 2 NH, C 2 H 5 CN, and C 2 H 6 and the rates of Zabka et al . [] for reactions between C 2 H 5 + and benzene, which have also been implemented in our model. Based on correlations detected between different mass species, Westlake et al also postulated several reaction pathways in which ions react with C 2 hydrocarbons (i.e., C 2 H 2 , C 2 H 4 , and C 2 H 6 ), resulting in higher mass ions.…”

Titan's ionospheric composition and structure: Photochemical modeling of Cassini INMS data

“…The ion‐neutral reaction production and loss is given by where k j is the ion neutral reaction rate, I j is the reactant ion density, and n j is the reactant neutral density. The reactions used come from the model of Vuitton et al [2007] with the additional reactions of methylenimine (CH 2 NH), propionitrile (C 2 H 5 CN), and benzene measured by Edwards et al [2008] and Zabka et al [2009]. A diagram of the primary chemical processes is shown in Figure 5.…”

Interaction of allylic carbocations with benzene: a theoretical model of carbocationic intermediates in terpene biosynthesis

“…[34][35][36][37][38] This information facilitates the design of biomimetic catalysts and new drugs as well as a better understanding of protein folding and function. 8,9,19,22,[39][40][41] Most of the previous studies of cation-π interactions with organic cations have used ammonium derivatives [19][20][21][22] and small cations 26,30,[42][43][44] as the probe molecule. It is known that coordinatively saturated cations interact with aromatic rings in a different manner than non-coordinatively saturated carbocations.…”