Hydrogen-atom Attack on Phenol and Toluene is ortho-directed

Authors

Olha Krechkivska, University of New South Wales
Callan M. Wilcox, University of New South Wales
Tyler P. Troy, University of SydneyFollow
Klaas Nauta, University of New South Wales
Bun Chan, University of Sydney
Rebecca Jacob, University of Sydney
Scott A. Reid, Marquette UniversityFollow
Leo Radom, University of Sydney
Timothy W. Schmidt, University of SydneyFollow
Scott H. Kable, University of New South Wales

Document Type

Article

Language

eng

Publication Date

2016

Publisher

Royal Society of Chemistry

Source Publication

Physical Chemistry Chemical Physics

Source ISSN

1463-9076

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).

Comments

Accepted version. Physical Chemistry Chemical Physics, Vol. 18, No. 12 (2016): 8625-8636. DOI. © 2016 Royal Society of Chemistry. Used with permission.

Recommended Citation

Krechkivska, Olha; Wilcox, Callan M.; Troy, Tyler P.; Nauta, Klaas; Chan, Bun; Jacob, Rebecca; Reid, Scott A.; Radom, Leo; Schmidt, Timothy W.; and Kable, Scott H., "Hydrogen-atom Attack on Phenol and Toluene is ortho-directed" (2016). Chemistry Faculty Research and Publications. 519.
https://epublications.marquette.edu/chem_fac/519