Updated chemical mechanism for atmospheric photooxidation of toluene

Leone, Joseph A.; Seinfeld, John H.

doi:10.1002/kin.550160207

Cited by 39 publications

(25 citation statements)

References 16 publications

(1 reference statement)

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“…0.4 x min-' was calculated. This value is about 60-70% of rates that have been estimated in the photochemical kinetics simulation models with stable products [18,291 and almost identical to the value used by Killus and Whitten [301 when assuming radical products. Because of the high reaction rate of HO' with benzaldehyde [42,431, this process predominates over photolysis loss in the CSTR (this ratio is estimated to be ca.…”

Section: Abstraction Pathwaymentioning

confidence: 80%

A continuous stirred tank reactor investigation of the gas‐phase reaction of hydroxyl radicals and toluene

Gery

Fox

Jeffries

et al. 1985

Int J of Chemical Kinetics

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A continuous stirred tank reactor (CSTR) was used to study the gas-phase reaction between H O and toluene. HO' was generated by the in situ photolysis of nitrous acid.Flow reactor operation at steady-state conditions with a residence time of 20 min allowed investigation of primary and very rapid secondary reactions. CSTR and batch reactor experiments were also performed with selected products. Both gas-phase and aerosol products were identified by chromatography and mass spectroscopy, with total product yields between 55 and 75% of reacted carbon. Toluene reaction products included cresols, nitrocresols, nitrotoluenes, 3,5-dinitrotouluene, benzaldehyde, benzyl nitrate, nitrophenols, methyl-p-benzoquinone, glyoxal, methylglyoxal, formaldehyde, methyl nitrate, PAN, and CO. The fraction of HO' methyl hydrogen abstraction was calculated to be 0.13 2 0.04. The ratio of reaction rate constants for nitrotoluene versus cresol formation from the HO-adduct was calculated to be about 3.3 x lo4. Also, the ratio of cresol formation versus 0, addition to the HO-adduct was estimated to be 20.5 for atmospheric conditions. Comparisons of these measurements with previous values and the implications with respect to photochemical kinetics modeling of the atmosphere are discussed.

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Section: Abstraction Pathwaymentioning

confidence: 80%

A continuous stirred tank reactor investigation of the gas‐phase reaction of hydroxyl radicals and toluene

Gery

Fox

Jeffries

et al. 1985

Int J of Chemical Kinetics

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“…However, there are important exceptions. First, there are families that actually emit both isoprenoids, although only monoterpenes are stored in permanent pools (Loreto and Fineschi, 2015). Second, emissions of isoprene and monoterpenes in the same plants may occur at different developmental stages.…”

Section: Monoterpenesmentioning

confidence: 99%

Field observations of volatile organic compound (VOC) exchange in red oaks

et al. 2017

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Abstract. Volatile organic compounds (VOCs) emitted by forests strongly affect the chemical composition of the atmosphere. While the emission of isoprenoids has been largely characterized, forests also exchange many oxygenated VOCs (oVOCs), including methanol, acetone, methyl ethyl ketone (MEK), and acetaldehyde, which are less well understood. We monitored total branch-level exchange of VOCs of a strong isoprene emitter (Quercus rubra L.) in a mixed forest in New England, where canopy-level fluxes of VOCs had been previously measured. We report daily exchange of several oVOCs and investigated unknown sources and sinks, finding several novel insights. In particular, we found that emission of MEK is linked to uptake of methyl vinyl ketone (MVK), a product of isoprene oxidation. The link was confirmed by corollary experiments proving in vivo detoxification of MVK, which is harmful to plants. Comparison of MEK, MVK, and isoprene fluxes provided an indirect indication of within-plant isoprene oxidation. Furthermore, besides confirming bidirectional exchange of acetaldehyde, we also report for the first time direct evidence of benzaldehyde bidirectional exchange in forest plants. Net emission or deposition of benzaldehyde was found in different periods of measurements, indicating an unknown foliar sink that may influence atmospheric concentrations. Other VOCs, including methanol, acetone, and monoterpenes, showed clear daily emission trends but no deposition. Measured VOC emission and deposition rates were generally consistent with their ecosystem-scale flux measurements at a nearby site.

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“…In addition, several ring-fragmentation products have been identified in various studies but never quantified (11). This information, along with several lmnthesized products, has been used to develop explicit mechanisms (9,26,34) for the atmospheriC oxidation of toluene as carried out in smog chambers. The intent of the work described in this thesis has been to more fully characterize the products of toluene'S atmospheric degradation.…”

Section: Chemical Processes Occurring In Sunlit Polluted Atm0stberesmentioning

confidence: 99%

“…In light of these considerations, najor products found in this study are: These conq:ounds' molecular protonated (Mi-l) ion intensity vary by less than an order of nagnitude. This implies that none of the identified products cDminates toluene's atmospheric degradation.This result contrasts with sorr.e of the current mechanisms in which only two of these new products have been included(9,26,34).WOO sp£:ctra ~ Tragmentation schemes Identifications listed in Table II are based mainly on the chemical-ionization/collision-induced-dissociation Each compound is found as a toluene reaction product and as a reaction product in each of the two deuterated toluene experinents. A compound's molecular weight and therefore its MH ion is shifted in the {:erdeuterated toluene experiment to a higher rcass depending on the number of hydrogens in its structure.…”

mentioning

confidence: 92%

“…MethY1gl$>xal. A ccnnp:lund of prine interest, based upon previous identifications(11) and proposed toluene-oxidation mechanisms(9,26,34), is methylglyoxal.Figure 12a-c gives the daughter spectra of the iO:1S in the mass S};:ectra of the toluene products which correspond to (M+ 1) of rrethyl glyoxal fomed fran the various isotopic forms of toluene. The spectra show loss of carbon monoxide, formaldehyde, and ketene, as sumnarized in Figure 12d.…”

mentioning

confidence: 99%

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Determination of toluene's degradation products under simulated atmospheric conditions

Dumdei

2000

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Previous work on toluene includes both product studies and proposed mechanisms. In all previous studies, the oombined product yields are half or less of the initially reacted toluene. A major reason for the poor carbon balances found in these studies is the precipitation of interrrediate reaction products fran the gas phase to the reaction walls. We have studied the oxidation process by blacklight irradiation of 1-10 ppm each of toluene and oxides of nitrogen in 22-liter pyrex flasks, in zero-air at 50% relative hmnidity. The flasks were pre-cleaned by baking at 350 C and the products were recovered from the walls by extraction with methanol or dichloromethane. Some gas-phase products were recovered in the solvent as well. The extracts were analyzed on a Finnigan MAT triple stage quadrllp)le mass spectraneter/ data systen by direct probe injection. Methane chemical ionization converted the products to Mf-l parent ions. The molecular weights of the products were determined fram the cr nass spectrmn, and also by the general survey methods of neutral loss and puent ion spectra. Once their molecular weights were determined, the products were fragmented by collision-induced-dissociation (CID) in the middle quadrupole to produce characteristic daughter ions. To assist in the spectral interpretation, toluene in three isomeric forms was subjected to simulated atmospheric reaction. In addition to normal (HS) toluene, methyl-deuterated (03) and per-deuterated (08) toluene were used. J This study confiDIled the existence of a number of products identified in past studies, confirmed the formation of same products which have been hyp:>thesized in several proposed mechaniSl"s for toluene oxidation, identified a nwnber of previously unidentified and unproposed products. In sane cases the fragmentation patterns didn' tallow cooice among several methylor hydroxyl-positional isaners, and undoubtedly rore than one isomer was often present, as would be expected. Detailed mechanistic steps have been outlined for all reaction products' fornation and destruction. other analytical techniques including GC, GC/MS, and HPLC, have supplanented the MS/MS analysis. These results and the further study of the types of compounds identified should nake a significant contribution to the understanding of atmostileric aranatic systens.

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Updated chemical mechanism for atmospheric photooxidation of toluene

Cited by 39 publications

References 16 publications

A continuous stirred tank reactor investigation of the gas‐phase reaction of hydroxyl radicals and toluene

A continuous stirred tank reactor investigation of the gas‐phase reaction of hydroxyl radicals and toluene

Field observations of volatile organic compound (VOC) exchange in red oaks

Determination of toluene's degradation products under simulated atmospheric conditions

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