Theoretical Studies on the Reaction Mechanism and Kinetics of Ethylbenzene-OH Adduct with O2 and NO2

Abstract

The OH-initiated reaction of ethylbenzene results in major OH addition, and the formed ethylbenzene-OH adducts subsequently react with O2 and NO2, which determine the components of the oxidation products. In this study, nine possible reaction paths of the most stable ethylbenzene-OH adduct, EB-Ortho (2-ethyl-hydroxycyclohexadienyl radical intermediate), with O2 and NO2 were studied using density functional theory and conventional transition state theory. The calculated results showed that ethyl-phenol formed via hydrogen abstraction was the major product of the EB-Ortho reaction with O2 under atmospheric conditions. Peroxy radicals generated from O2 added to EB-Ortho could subsequently react with NO and O2 to produce 5-ethyl-6-oxo-2,4-hexadienal, furan, and ethyl-glyoxal, respectively. However, nitro-ethylbenzene formed from NO2 addition to EB-Ortho was the predominant product of the EB-Ortho reaction with NO2 at room temperature. The total calculated rate constant of the EB-Ortho reaction with O2 and NO2 was 9.57 × 10−16 and 1.78 × 10−11 cm3 molecule−1 s−1, respectively, approximately equivalent to the experimental rate constants of toluene-OH adduct reactions with O2 and NO2. This study might provide a useful theoretical basis for interpreting the oxygen-containing and nitrogen-containing organics in anthropogenic secondary organic aerosol particles.

OH Radical and Chlorine Atom Kinetics of Substituted Aromatic Compounds: 4-Chlorobenzotrifluoride (p-ClC6H4CF3)

“…However, there remains limited insight into the reaction mechanisms and the formation of pre-reactive complexes, OH-aromatic adduct formation and thermal stability, as well as degradation products. More recently, theoretical methods have been used to interpret the reaction potential energy surface (PES) of these reactions, [5][6][7] but the ability to validate the calculations by comparison with experimental data is rather limited. 4-chlorobenzotrifluoride (C7H4ClF3, para-chlorobenzotrifluoride, PCBTF) (see Figure 1) is a volatile chemical product (VCP) used in solvent-based coatings, e.g.…”

Theoretical Chemistry of Atmospheric Processes

“…In this Special Issue on "Theoretical Chemistry of Atmospheric Processes", five original research articles report recent findings describing the modelling of reactions and processes taking place in the atmosphere, while a review finishes this Special Issue. The research articles span a variety of subjects: N 2 + H 2 reactive collisions [1], sulfuric acid-base cluster formation [2], the reaction mechanism of ethylbenzene-OH adduct with O 2 and NO 2 [3], kinetics of reactions of ozone with halogen atoms (Cl, Br and I) [4] and an empirical model for ozone concentration highlighting the roles of isoprene and monoterpenes [5]. Finally, a review paper presents us a proposal for a programme of research for theoretical chemistry where atmospheric turbulence is properly discussed [6].…”

“…In the third piece, Zhang et al [3] use density functional theory and conventional transition state theory to study the reaction mechanism and kinetics of the most stable ethylbenzene-OH adduct (EB-Ortho) with O 2 and NO 2 . The authors suggest nine possible pathways, three for EB-Ortho + O 2 and six for EB-Ortho + NO 2 .…”