title: Hydrogen-atom attack on phenol and toluene is ortho-directed.
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).
authors.affiliation: School of Chemistry, University of New South Wales, Kensington, NSW 2052, Australia. s.kable@unsw.edu.au.
authors.forename: Olha
authors.initials: O
authors.lastname: Krechkivska
authors.affiliation: School of Chemistry, University of New South Wales, Kensington, NSW 2052, Australia. s.kable@unsw.edu.au.
authors.forename: Callan M
authors.initials: CM
authors.lastname: Wilcox
authors.affiliation: School of Chemistry, University of Sydney, Sydney, NSW 2006, Australia.
authors.forename: Tyler P
authors.initials: TP
authors.lastname: Troy
authors.affiliation: School of Chemistry, University of New South Wales, Kensington, NSW 2052, Australia. s.kable@unsw.edu.au.
authors.forename: Klaas
authors.initials: K
authors.lastname: Nauta
authors.affiliation: School of Chemistry, University of Sydney, Sydney, NSW 2006, Australia.
authors.forename: Bun
authors.initials: B
authors.lastname: Chan
authors.affiliation: School of Chemistry, University of Sydney, Sydney, NSW 2006, Australia.
authors.forename: Rebecca
authors.initials: R
authors.lastname: Jacob
authors.affiliation: Department of Chemistry, Marquette University, Milwaukee, WI 53201, USA.
authors.forename: Scott A
authors.initials: SA
authors.lastname: Reid
authors.affiliation: School of Chemistry, University of Sydney, Sydney, NSW 2006, Australia.
authors.forename: Leo
authors.initials: L
authors.lastname: Radom
authors.affiliation: School of Chemistry, University of New South Wales, Kensington, NSW 2052, Australia. s.kable@unsw.edu.au.
authors.forename: Timothy W
authors.initials: TW
authors.lastname: Schmidt
authors.affiliation: School of Chemistry, University of New South Wales, Kensington, NSW 2052, Australia. s.kable@unsw.edu.au.
authors.forename: Scott H
authors.initials: SH
authors.lastname: Kable