Related Experiment Video
Updated: May 26, 2026

Efficient Synthesis of Polyfunctionalized Benzenes in Water via Persulfate-promoted Benzannulation of α,β-Unsaturated Compounds and Alkynes
Published on: December 16, 2019
Isomerization and dissociation of n-butylbenzene radical cation
Stéphanie Halbert1, Guy Bouchoux
1Laboratoire des Mécanismes Réactionnels, Ecole Polytechnique, CNRS, 91128 Palaiseau, France.
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.
Related Concept Videos
Benzene to 1,4-Cyclohexadiene: Birch Reduction Mechanism
Reduction of Benzene to Cyclohexane: Catalytic Hydrogenation
Reactions at the Benzylic Position: Oxidation and Reduction
Nucleophilic Aromatic Substitution: Elimination–Addition
Electrophilic 1,2- and 1,4-Addition of X2 to 1,3-Butadiene
Benzene to Phenol via Cumene: Hock Process

