title: Gas-phase reaction of hydroxyl radical with hexamethylbenzene.
abstract: Aromatic hydrocarbons are important components of polluted ambient air. The reaction of OH radicals with hexamethylbenzene (HMB) is a prototype system to study ipso addition leading eventually to dealkylation. We have investigated the OH + HMB and OD + HMB reactions between 323 and 433 K using a discharge fast-flow reactor coupled to a time-of-flight mass spectrometer with single-photon VUV photoionization (10.54 eV). The H atom abstraction channel has been found to be equal to (13.7 ± 4.4) % at 330 K leading to (11.1 ± 3.6) % at 298 K, higher than predicted by commonly used structure-reactivity relationships. The back dissociation rate constant has also been measured and has been found to be smaller than the rate of other aromatic hydrocarbons, in good agreement with density functional theoretical calculations. The dealkylation channel, leading to pentamethylphenol (PMP) + CH(3), is always found to be the minor channel, estimated inferior to 2% at 298 K.
authors.affiliation: Universite Bordeaux, ISM, UMR 5255, F-33400 Talence, France. jc.loison@ism.u-bordeaux1.fr
authors.forename: Jean-Christophe
authors.initials: JC
authors.lastname: Loison
authors.forename: Marie-Thérèse
authors.initials: MT
authors.lastname: Rayez
authors.forename: Jean-Claude
authors.initials: JC
authors.lastname: Rayez
authors.forename: Aline
authors.initials: A
authors.lastname: Gratien
authors.forename: Pranay
authors.initials: P
authors.lastname: Morajkar
authors.forename: Christa
authors.initials: C
authors.lastname: Fittschen
authors.forename: Eric
authors.initials: E
authors.lastname: Villenave