Heterogeneous reactions of ozone with methoxyphenols, in presence and absence of light (original) (raw)
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Heterogeneous light-induced ozone processing on the organic coatings in the atmosphere
Atmospheric Environment, 2009
Many of the more recent studies concerning heterogeneous reactions of atmospheric interest, carry, in some cases, much more details but still follow the basic philosophy of the first pioneering studies. Therefore, in this study the accent is put on the additional complexities that arise when the aerosols of interest have more complex compositions. Hence, it is attempted to identify the products following the simultaneous ozone processing and light irradiation on particles coated with 4-phenoxyphenol in the presence of 4-carboxybenzophenone as a photosensitizer. In order to reveal a more complete picture on the fate of these aromatic compounds under controlled experimental conditions, different analytical tools such as gas chromatography coupled to mass spectrometry (GC-MS) and proton transfer reactionmass spectrometry (PTR-MS) have been applied. Several surface bound products were identified via GC-MS and some of them (phenol, hydroquinone, catechol, 4-hydroxybenzoic acid, benzoic acid, fumaric acid, terephthalic acid, maleic acid, 1,2,4-trihydroxybenzene and 4,4 0 -oxydiphenol) confirmed with standards. The main volatile secondary products as identified by PTR-MS in this study were formic acid, phenol and p-benzoquinone. A reaction mechanism was proposed and density functional theory calculations were performed in order to elucidate the initial steps of the ozonolysis reaction on 4-phenoxyphenol in the presence of 4-carboxybenzophenone.
Atmospheric Environment, 2010
For the first time we investigated the effect of solar irradiation upon the heterogeneous ozonation of adsorbed 3,4,5-trimethoxybenzaldehyde on solid surface. Light-induced heterogeneous reactions between gas-phase ozone and 3,4,5-trimethoxybenzaldehyde adsorbed on silica particles were performed and the consecutive reaction products were identified. At an ozone mixing ratio of 250 ppb, the loss of 3,4,5-trimethoxybenzaldehyde ranged from 1.0 $ 10 À6 s À1 in the dark to 2.9 $ 10 À5 s À1 under light irradiation. Such large enhancement of 29 times clearly shows the importance of light (l > 300 nm) during the heterogeneous ozonolysis on organic coated particles.
Atmospheric Chemistry and Physics, 2014
In the present study, campholenic aldehyde ozonolysis was performed to investigate pathways leading to specific biogenic secondary organic aerosol (SOA) marker compounds. Campholenic aldehyde, a known α-pinene oxidation product, is suggested to be a key intermediate in the formation of terpenylic acid upon α-pinene ozonolysis. It was reacted with ozone in the presence and absence of an OH radical scavenger, leading to SOA formation with a yield of 0.75 and 0.8, respectively. The resulting oxidation products in the gas and particle phases were investigated employing a denuder/filter sampling combination. Gas-phase oxidation products bearing a carbonyl group, which were collected by the denuder, were derivatised by 2,4-dinitrophenylhydrazine (DNPH) followed by liquid chromatography/negative ion electrospray ionisation time-of-flight mass spectrometry analysis and were compared to the gas-phase compounds detected by online protontransfer-reaction mass spectrometry. Particle-phase products were also analysed, directly or after DNPH derivatisation, to derive information about specific compounds leading to SOA formation. Among the detected compounds, the aldehydic precursor of terpenylic acid was identified and its presence was confirmed in ambient aerosol samples from the DNPH derivatisation, accurate mass data, and additional mass spectrometry (MS 2 and MS 3 fragmentation studies). Furthermore, the present investigation sheds light on a reaction pathway leading to the formation of terpenylic acid, involving α-pinene, α-pinene oxide, campholenic aldehyde, and terpenylic aldehyde. Additionally, the formation of diaterpenylic acid acetate could be connected to campholenic aldehyde oxidation. The present study also provides insights into the source of other highly functionalised oxidation prod-ucts (e.g. m / z 201, C 9 H 14 O 5 and m / z 215, C 10 H 16 O 5 ), which have been observed in ambient aerosol samples and smog chamber-generated monoterpene SOA. The m / z 201 and 215 compounds were tentatively identified as a C 9 -and C 10 -carbonyl-dicarboxylic acid, respectively, based on reaction mechanisms of campholenic aldehyde and ozone, as well as detailed interpretation of mass spectral data, in conjunction with the formation of corresponding DNPH derivatives.
Journal of Atmospheric Chemistry, 2006
This article presents a complete study of the diurnal chemical reactivity of the biogenic volatile organic compound (BVOC), 2-methyl-3-buten-2-ol (MBO) in the troposphere. Reactions of MBO with OH and with ozone were studied to analyse the respective parts of both processes in the global budget of MBO atmospheric reactivity. They were investigated under controlled conditions for pressure (atmospheric pressure) and temperature (298 ± 2 K) using three complementary European simulation chambers. Reaction with OH radicals was studied in the presence of and in the absence of NO x . The kinetic study was carried out by relative rate study using isoprene as a reference. The rate constant found for this reaction was k MBOþOH ¼ 5:6 AE 0:6 ð ÞÂ10 À11 molecule −1 cm 3 s −1 . FTIR spectroscopy, DNPH-and PFBHA-derivatisation analyses were performed for reactions with both OH radicals and ozone. In both reactions, the hydroxycarbonyl compound, 2-hydroxy-2-methylpropanal (HMPr) was positively identified and quantified, with a yield of R HM Pr ¼ 0:31 AE 0:11 in the reaction with OH, and a yield of R HM Pr ¼ 0:43 AE 0:12 and 0.84±0.08 in the reaction with ozone under dry (HR<1%) and humid conditions (HR=20%-30%). A primary production of two other carbonyl compounds, acetone R acetone ¼ 0:39 AE 0:22, and formaldehyde R HCHO ¼ 0:44 AE 0:05 was found in the case of the dry ozonolysis experiments. Under humid conditions, only formaldehyde was co-produced with HMPr as a primary carbonyl compound, with a yield of R HCHO ¼ 0:55 AE 0:03. For the reaction with OH, three other carbonyl compounds were detected, acetone R acetone ¼ 0:67 AE 0:05, formaldehyde R HCHO ¼ 0:33 AE 0:08 and glycolaldehyde R glycolaldehyde ¼ 0:78 AE 0:20. In addition some realistic photo-oxidation experiments were performed to understand in an overall way the transformations of MBO in the atmosphere. The realistic photo-oxidation experiments were conducted in the EUPHORE J Atmos Chem outdoor simulation chamber. It was found that this compound is a weak secondary aerosol producer (less than 1% of the carbon balance). But it was confirmed that it is a potentially significant source of acetone, Δ[Acetone]/Δ[MBO]=0.45. With our experimental conditions ([MBO] 0 =200 ppb, [NO]o=50 ppb), an ozone yield of Δ[O 3 ]/Δ[MBO]=1.05 was found.
Environmental Science & Technology, 2003
This study examines the primary and secondary products resulting from reactions initiated by adding ozone to complex mixtures of volatile organic compounds (VOC). The mixtures were representative of organic species typically found indoors, but the concentrations tended to be higher than normal indoor levels. Each 4-h experiment was conducted in a controlled environmental facility (CEF, 25 m 3 ) ventilated at ∼1.8 h -1 . The mixture investigated included 23 VOC (no O 3 ), O 3 /23 VOC, O 3 /21 VOC (no d-limonene or R-pinene), and O 3 /terpene only (d-limonene and R-pinene). The net O 3 concentration was ∼40 ppb in each experiment, and the total organic concentration was 26 mg/m 3 for the 23 VOC mixture, 25 mg/m 3 for the 21 VOC mixture, and 1.7 mg/m 3 for the d-limonene and R-pinene mixture. When the 23 VOC were added to the CEF containing no O 3 , no compounds other than those deliberately introduced were observed. When O 3 was added to the CEF containing the 23 VOC mixture, both gas and condensed phase products were found, including aldehydes, organic acids, and submicron particles (140 µg/m 3 ). When O 3 was added to the CEF containing the 21 VOC without the two terpenes (O 3 /21 VOC condition), most of the products that were observed in the O 3 /23 VOC experiments were no longer present or present at much lower concentrations. Furthermore, the particle mass concentration was 2-7 µg/ m 3 , indistinguishable from the background particle concentration level. When O 3 was added to the CEF containing only two terpenes, the results were similar to those in the O 3 /23 VOC experiments, but the particle mass concentration (190 µg/m 3 ) was higher. The results indicate that (i) O 3 reacts with unsaturated alkenes under indoor conditions to generate submicron particles and other potentially irritating species, such as aldehydes and organic acids; (ii) the major chemical transformations that occurred under our experimental conditions were driven by O 3 /dlimonene and O 3 /R-pinene reactions; and (iii) the hydroxyl radicals (OH) that were generated from the O 3 /terpene reactions played an important role in the chemical transformations and were responsible for approximately 56-70% of the formaldehyde, almost all of the p-tolualdehyde, and 19-29% of the particle mass generated in these experiments.
Photoenhanced degradation of veratraldehyde upon the heterogeneous ozone reactions
Physical Chemistry Chemical Physics, 2010
Light-induced heterogeneous reactions between gas-phase ozone and veratraldehyde adsorbed on silica particles were performed. At an ozone mixing ratio of 250 ppb, the loss of veratraldehyde largely increased from 1.81 Â 10 À6 s À1 in the dark to 2.54 Â 10 À5 s À1 upon exposure to simulated sunlight (l 4 300 nm). The observed rates of degradation exhibited linear dependence with the ozone in the dark ozonolysis experiments which change in the non-linear Langmuir-Hinshelwood dependence in the experiments with simultaneous ozone and light exposure of the coated particles. When the coated silica particles were exposed only to simulated sunlight in absence of ozone the loss of veratraldehyde was about three times higher i.e. 5.97 Â 10 À6 s À1 in comparison to the ozonolysis experiment under dark conditions at 250 ppb ozone mixing ratio, 1.81 Â 10 À6 s À1 .
Formation of secondary organic aerosol and oligomers from the ozonolysis of enol ethers
Atmospheric Chemistry and Physics, 2006
Formation of secondary organic aerosol has been observed in the gas phase ozonolysis of a series of enol ethers, among them several alkyl vinyl ethers (AVE, ROCH=CH 2 ), such as ethyl, propyl, n-butyl, i so-butyl, t-butyl vinyl ether, and ethyl propenyl ether (EPE, C 2 H 5 OCH=CHCH 3 ). The ozonolysis has been studied in a 570 l spherical glass 5 20 oligomeric structure and chain unit identity are confirmed by HPLC/ESI(+)/MS-TOF and ESI(+)/MS/MS-TOF experiments, whereby successive and systematic loss of a fragment with mass 46 for the AVE (and mass 60 for EPE) is observed. It is proposed that the oligomer has the following basic structure of an oligoperoxide, -[CH(R)-O-O] n -, where R=H for the AVE and R=CH 3 for the EPE. Oligoperoxide formation is thus sug-25 gested to be another, so far unknown reaction of stabilized Criegee Intermediates in the gas phase ozonolysis of oxygen-containing alkenes leading to SOA formation.
Gas-phase products and secondary aerosol yields from the photooxidation of 16 different terpenes
Journal of Geophysical Research, 2006
1] The ozonolyses of six monoterpenes (a-pinene, b-pinene, 3-carene, terpinolene, a-terpinene, and myrcene), two sesquiterpenes (a-humulene and b-caryophyllene), and two oxygenated terpenes (methyl chavicol and linalool) were conducted individually in Teflon chambers to examine the gas-phase oxidation product and secondary organic aerosol (SOA) yields from these reactions. Particle size distribution and number concentration were monitored and allowed for the calculation of the SOA yield from each experiment, which ranged from 1 to 54%. A proton transfer reaction mass spectrometer (PTR-MS) was used to monitor the evolution of gas-phase products, identified by their mass to charge ratio (m/z). Several gas-phase oxidation products, formaldehyde, acetaldehyde, formic acid, acetone, acetic acid, and nopinone, were identified and calibrated. Aerosol yields, and the yields of these identified and calibrated oxidation products, as well as many higher m/z oxidation products observed with the PTR-MS, varied significantly between the different parent terpene compounds. The sum of measured oxidation products in the gas and particle phase ranged from 33 to 77% of the carbon in the reacted terpenes, suggesting there are still unmeasured products from these reactions. The observations of the higher molecular weight oxidation product ions provide evidence of previously unreported compounds and their temporal evolution in the smog chamber from multistep oxidation processes. Many of the observed ions, including m/z 111 and 113, have also been observed in ambient air above a Ponderosa pine forest canopy, and our results confirm they are consistent with products from terpene + O 3 reactions. Many of these products are stable on the timescale of our experiments and can therefore be monitored in field campaigns as evidence for ozone oxidative chemistry.
Zeitschrift für Physikalische Chemie, 2010
The gas-phase ozonolysis of the biogenic unsaturated compounds 1-penten-3-ol, (Z)-2-penten-1-ol and 1-penten-3-one has been investigated in two atmospheric simulation chambers. The following rate coefficients (in units of 10 K17 cm 3 molecule K1 s K1 ) were determined at atmospheric pressure and 293±2 K using an absolute rate method: 1-penten-3-ol, (1.64±0.15); (Z)-2penten-1-ol, (11.5±0.66); 1-penten-3-one, (1.17±0.15). Reaction products were identified by in situ FTIR spectroscopy and gas chromatographymass spectrometry (GC-MS). The major products and their average molar yields in the presence of a radical scavenger at relative humidity < 1% were: formaldehyde (0.49±0.02), 2-hydroxybutanal (0.46±0.03) and propanal (0.15±0.02) from 1-penten-3-ol; propanal (0.39±0.03) and glycolaldehyde (0.43±0.04) from (Z)-2-penten-1-ol; formaldehyde (0.37±0.02) and 2-oxobutanal (0.49±0.03) from 1-penten-3one. The formation of secondary organic aerosol was also observed with yields ranging from 0.13-0.17 for the unsaturated alcohols. Significantly lower yields of around 0.03 were measured for 1-penten-3-one. The results of this work are used to determine atmospheric lifetimes and reaction mechanisms for the gas-phase ozonolysis of 1-penten-3-ol, (Z)-2-penten-1-ol and 1penten-3-one. The broader atmospheric implications of this work are also discussed.