Bond-formation versus electron transfer: C-C-coupling reactions of hydrocarbon dications with benzene.
The bimolecular reactions of several hydrocarbon dications C(m)H(n)(2+) (m = 6-10, n = 4-9) with neutral benzene are investigated by tandem mass spectrometry using a multipole instrument. Not surprisingly, the major reaction of C(m)H(n)(2+) with benzene corresponds to electron transfer from the neutral arene to the dication resulting in the pair of monocationic products C(m)H(n)(+) + C(6)H(6)(+). In addition, also dissociative electron transfer takes place, whereas proton transfer from the C(m)H(n)(2+) dication to neutral benzene is almost negligible. Interestingly, the excess energy liberated upon electron transfer from the neutral arene to the C(m)H(n)(2+) dication is not equally partitioned in the monocationic products in that the cations arising from the dicationic precursor have a higher internal energy content than the monocations formed from the neutral reaction partner. In addition to the reactions leading to monocationic product ions, bond-forming reactions with maintenance of the two-fold charge are observed, which lead to a condensation of the C(m)H(n)(2+) dications with neutral benzene under formation of intermediate C(m+6)H(n+6)(2+) species and then undergo subsequent losses of molecular hydrogen or neutral acetylene. This reaction complements a recently proposed dicationic route for the formation of polycyclic aromatic hydrocarbons under extreme conditions such as they exist in interstellar environments.
Roithová
Jana
J
Institute of Organic Chemistry and Biochemistry, Flemingovo nám 2, 16610, Prague 6, Czech Republic.
Schröder
Detlef
D
D001554:Benzene / Q000737:chemistry*; D002412:Cations / Q000737:chemistry; D004583:Electrons; D006838:Hydrocarbons / Q000737:chemistry*; D013058:Mass Spectrometry / Q000379:methods; D010084:Oxidation-Reduction; D012680:Sensitivity and Specificity
D002412:Cations; D006838:Hydrocarbons; D001554:Benzene