Gas‐phase reaction of hydroxyl radicals with m‐, o‐ and p‐cresol

Abstract

The gas-phase reaction of oxygenated aromatic compounds m-cresol, o -cresol, and p-cresol with hydroxyl radicals has been studied by GC-MS. Experiments have been performed in a large-volume photoreactor (8000 L) at 294 ± 2 K and atmospheric pressure. The relative kinetic method was used to determine the rate constants for these reactions, with 1,3,5-trimethylbenzene as a reference compound. The rate constants obtained are k OH (mcresol) = (5.88 ± 0.92) × 10 −11 cm 3 molecule −1 s −1 , k O H (o -cresol) = (4.32 ± 0.52) × 10 −11 cm 3 molecule −1 s −1 , and k O H ( p-cresol) = (4.96 ± 0.75) × 10 −11 cm 3 molecule −1 s −1 . The degradation products observed and their respective molar yields were methyl-1,4-benzoquinone 12.4 ± 1.2%, 5-methyl-2-nitrophenol 1.5 ± 0.3%, and 3-methyl-2-nitrophenol 1.4 ± 0.3% from m-cresol, methyl-1,4-benzoquinone 5.6 ± 0.9%, and 6-methyl-2-nitrophenol 4.7 ± 0.8% from o -cresol, and 4-methyl-2-nitrophenol 17.2 ± 2.5% from p-cresol. This kinetic and product data are compared with the literature, and the reaction mechanisms are discussed. Our results are in accordance with the previous studies (Atkinson,

Reassessing the atmospheric oxidation mechanism of toluene

“…As is evident from Table 2, our calculations of the energetics, rate constants, and branching ratios for the OH−toluene reactions compare favorably with the previously available experimental and theoretical results, considering the respective uncertainties. For example, our calculated rate coefficient of 4.3 × 10 −11 cm 3 ·molecule −1 ·s −1 for OH addition to o-cresol to form the DHMB radical is in agreement with the experimental value of (4.3 ± 0.5) × 10 −11 cm 3 ·molecule −1 ·s −1 by CoeurTourneur et al (41). Additional structural parameters for the reactants, key intermediates, transition states, and products involved in the OH−toluene reaction system are shown in SI Appendix, Fig.…”

Investigation of the degradation of cresols in the treatments with ozone

“…Although most of these products can be generated from the ozonation of several aromatic substrates, including substituted phenols, and also from the oxidation of cresols by photoelectrochemical Fenton treatments (Pimentel, 2010;Flox et al, 2007), the characterization of cresols' degradation products was generally limited to those preceding ring cleavage (Wang et al, 1998;Olariu et al, 2002;Coeur-Tourneur et al, 2006). Ring cleavage byproducts generally originate in the final steps of an extensive oxidation process and are possibly too polar and hydrophilic to be efficiently extracted from the water matrix and/or detected with reasonable sensitivity.…”

“…In the few studies concerning cresols, the oxidation of the methyl group was not reported, whereas various hydroxylation products of the aromatic ring (methylcathecols, methylhydroquinone, methylbenzoquinone) were identified (Olariu et al, 2002;Coeur-Tourneur et al, 2006). The same products were observed when the electro-Fenton process was used instead of ozone to oxidize cresols (Pimentel, 2010;Pimentel et al, 2008;Oturan et al, 2008).…”

On the internal rotations in p-cresol in its ground and first electronically excited states

“…10 The present publication concludes a series of combined microwave and quantum chemical studies on cresols. 11,12 p-cresol is currently under investigation in very different fields of chemistry: In atmospheric chemistry as a precursor for the formation of photo-oxidants and secondary organic aerosols, 13 in clinical chemistry for its influence on kidney failures, 14 and in food chemistry where p-cresol has been spotted to have an influence on the composition of the aroma of cheddar cheese. 15 For para substituted toluenes with a C 6 symmetry of the internal rotor ͑toluene, 16 p-fluorotoluene, 17 and p-chlorotoluene 18 ͒, very low barriers hindering the methyl torsion of less than 5 cm −1 were found.…”