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Issue 12, 2016
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Hydrogen-atom attack on phenol and toluene is ortho-directed

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Abstract

The reaction of H + phenol and H/D + toluene has been studied in a supersonic expansion after electric discharge. The (1 + 1′) resonance-enhanced multiphoton ionization (REMPI) spectra of the reaction products, at m/z = parent + 1, or parent + 2 amu, were measured by scanning the first (resonance) laser. The resulting spectra are highly structured. Ionization energies were measured by scanning the second (ionization) laser, while the first laser was tuned to a specific transition. Theoretical calculations, benchmarked to the well-studied H + benzene → cyclohexadienyl radical reaction, were performed. The spectrum arising from the reaction of H + phenol is attributed solely to the ortho-hydroxy-cyclohexadienyl radical, which was found in two conformers (syn and anti). Similarly, the reaction of H/D + toluene formed solely the ortho isomer. The preference for the ortho isomer at 100–200 K in the molecular beam is attributed to kinetic, not thermodynamic effects, caused by an entrance channel barrier that is ∼5 kJ mol−1 lower for ortho than for other isomers. Based on these results, we predict that the reaction of H + phenol and H + toluene should still favour the ortho isomer under elevated temperature conditions in the early stages of combustion (200–400 °C).

Graphical abstract: Hydrogen-atom attack on phenol and toluene is ortho-directed

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Publication details

The article was received on 10 Dec 2015, accepted on 29 Feb 2016 and first published on 29 Feb 2016


Article type: Paper
DOI: 10.1039/C5CP07619F
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Citation: Phys. Chem. Chem. Phys., 2016,18, 8625-8636
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    Hydrogen-atom attack on phenol and toluene is ortho-directed

    O. Krechkivska, C. M. Wilcox, T. P. Troy, K. Nauta, B. Chan, R. Jacob, S. A. Reid, L. Radom, T. W. Schmidt and S. H. Kable, Phys. Chem. Chem. Phys., 2016, 18, 8625
    DOI: 10.1039/C5CP07619F

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