Product Study of the OH, NO3, and O3 Initiated Atmospheric Photooxidation of Propyl Vinyl Ether (original) (raw)
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Gas-phase degradation of organic compounds in the troposphere
Pure and Applied Chemistry, 2000
The present status of knowledge of the gas-phase reactions of selected classes of volatile non-methane organic compounds (NMOCs) [alkanes, alkenes, aromatic hydrocarbons, oxygen-containing NMOCs and nitrogen-containing NMOCs] and their degradation products in the troposphere is briefly discussed. In the troposphere, NMOCs can undergo photolysis, reaction with the hydroxyl (OH) radical during daylight hours, reaction with the nitrate (NO3) radical (primarily during nighttime), reaction with ozone (03), and, in certain situations, reaction with the chlorine (Cl) atom. The kinetics and mechanisms of the initial OH radical, NO3 radical and O3 reactions are reasonably well understood. However, the subsequent reactions of the organic radicals formed after the initial OH radical, NO3 radical and 0 3 reactions are in many cases much less well understood, and photolysis of NMOCs under tropospheric conditions is in general a poorly understood area. In the tropospheric degradations of NMOCs, the important intermediate radicals are alkyl or substituted alkyl radicals (R), alkyl peroxy or substituted alkyl peroxy radicals (R 0 2), and alkoxy or substituted alkoxy radicals (R 0). While much progress has been made in elucidating the reactions of organic peroxy and alkoxy radicals, the mechanisms of the gas-phase reactions of 0 3 with alkenes, and the mechanisms and products of the OH radical-initiated reactions of aromatic hydrocarbons, there are still areas of uncertainty which impact the ability to accurately model the tropospheric degradations of NMOCs and to predict the products formed. These will be discussed.
Environmental Science & Technology, 2012
The products formed from the reactions of OH radicals with vinyl acetate and allyl acetate have been studied in a 1080 L quartz-glass chamber in the presence and absence of NO x using in situ FTIR spectroscopy to monitor the reactant decay and product formation. The yields of the primary products formed in the reaction of OH with vinyl acetate were: formic acetic anhydride (84 ± 11)%; acetic acid (18 ± 3)% and formaldehyde (99 ± 15)% in the presence of NO x and formic acetic anhydride (28 ± 5)%; acetic acid (87 ± 12)% and formaldehyde (52 ± 8)% in the absence of NO x. For the reaction of OH with allyl acetate the yields of the identified products were: acetoxyacetaldehyde (96 ± 15)% and formaldehyde (90 ± 12)% in the presence of NO x and acetoxyacetaldehyde (26 ± 4)% and formaldehyde (12 ± 3)% in the absence of NO x. The present results indicate that in the absence of NO x the main fate of the 1,2-hydroxyalkoxy radicals formed after addition of OH to the double bond in the compounds is, in the case of vinyl acetate, an α-ester rearrangement to produce acetic acid and CH 2 (OH)CO • radicals and in the case of allyl acetate reaction of the radical with O 2 to form acetic acid 3-hydroxy-2-oxo-propyl ester (CH 3 C(O)OCH 2 C(O)-CH 2 OH). In contrast, in the presence of NO x the main reaction pathway for the 1,2-hydroxyalkoxy radicals is decomposition. The results are compared with the available literature data and implications for the atmospheric chemistry of vinyl and allyl acetate are assessed.
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.
2020
The kinetics of the gas phase reactions of hydroxyl radicals with two unsaturated ketoethers (UKEs) at (298 ± 3) K and 1 atm of synthetic air have been studied for the first time using the relative-rate technique in an environmental reaction chamber by in situ Fourier-transform infrared spectroscopy (FTIR). The rate coefficients obtained using propene and isobutene as reference compounds were (in units of 10 −10 cm 3 molecule −1 s −1) as follows: k TMBO (OH + (E)-4-methoxy-3-buten-2-one) = (1.41 ± 0.11) and k MMPO (OH + (1E)-1-methoxy-2-methyl-1-penten-3-one) = (3.34 ± 0.43). In addition, quantification of the main oxidation products in the presence of NO x has been performed, and degradation mechanisms for these reactions were developed. Methyl formate, methyl glyoxal, peroxyacetyl nitrate (PAN) and peroxypropionyl nitrate (PPN) were identified as main reaction products and quantified for both reactions. The results of the present study provide new insights regarding the contribution of these multifunctional volatile organic compounds (VOCs) in the generation of secondary organic aerosols (SOAs) and long-lived nitrogen containing compounds in the atmosphere. Atmospheric lifetimes and implications are discussed in light of the obtained results.
Atmospheric Photochemical Degradation of 1,4-Unsaturated Dicarbonyls
Environmental Science & Technology, 1999
The elucidation of details of photochemical reaction mechanisms for the oxidation of aromatic volatile organic compounds remains a major problem (1). This is because there are apparently a large variety of photooxidation products formed in the reactions. Each of these products further reacts apparently in ways that are different from the better-understood alkane and simple alkene monofuctional products. The total reacted carbon balance is still poor in the aromatic systems, mostly because of lack of appropriate analytical methods for detecting the product mixtures of those photochemical reactions.
The Journal of Physical Chemistry A, 1998
Pulse radiolysis and FT-IR smog chamber experiments were used to investigate the atmospheric fate of C 6 H 5 O(•) radicals. Pulse radiolysis experiments gave σ(C 6 H 5 O(•)) 235 nm) (3.82 (0.48) × 10-17 cm 2 molecule-1 , k(C 6 H 5 O(•) + NO)) (1.88 (0.16) × 10-12 , and k(C 6 H 5 O(•) + NO 2)) (2.08 (0.15) × 10-12 cm 3 molecule-1 s-1 at 296 K in 1000 mbar of SF 6 diluent. No discernible reaction of C 6 H 5 O(•) radicals with O 2 was observed in smog chamber experiments, and we derive an upper limit of k(C 6 H 5 O(•) + O 2) < 5 × 10-21 cm 3 molecule-1 s-1 at 296 K. These results imply that the atmospheric fate of phenoxy radicals in urban air masses is reaction with NO x. Density functional calculations and gas chromatography-mass spectrometry are used to identify 4-phenoxyphenol as the major product of the self-reaction of C 6 H 5 O(•) radicals. As part of this study, relative rate techniques were used to measure rate constants for reaction of Cl atoms with phenol [k(Cl + C 6 H 5 OH)) (1.93 (0.36) × 10-10 ], several chlorophenols [k(Cl + 2-chlorophenol)) (7.32 (1.30) × 10-12 , k(Cl + 3-chlorophenol)) (1.56 (0.21) × 10-10 , and k(Cl + 4-chlorophenol)) (2.37 (0.30) × 10-10 ], and benzoquinone [k(Cl + benzoquinone)) (1.94 (0.35) × 10-10 ], all in units of cm 3 molecule-1 s-1. A reaction between molecular chlorine and C 6 H 5 OH to produce 2-and 4-chlorophenol in yields of (28 (3)% and (75 (4)% was observed. This reaction is probably heterogeneous in nature, and an upper limit of k(Cl 2 + C 6 H 5 OH) e 1.9 × 10-20 cm 3 molecule-1 s-1 was established for the homogeneous component. These results are discussed with respect to the previous literature data and to the atmospheric chemistry of aromatic compounds.
Chemical Composition of Secondary Organic Aerosol Formed from the Photooxidation of Isoprene
The Journal of Physical Chemistry A, 2006
Recent work in our laboratory has shown that the photooxidation of isoprene (2-methyl-1,3-butadiene, C 5 H 8 ) leads to the formation of secondary organic aerosol (SOA). In the current study, the chemical composition of SOA from the photooxidation of isoprene over the full range of NO x conditions is investigated through a series of controlled laboratory chamber experiments. SOA composition is studied using a wide range of experimental techniques: electrospray ionization-mass spectrometry, matrix-assisted laser desorption ionization-mass spectrometry, high-resolution mass spectrometry, online aerosol mass spectrometry, gas chromatography/mass spectrometry, and an iodometric-spectroscopic method. Oligomerization was observed to be an important SOA formation pathway in all cases; however, the nature of the oligomers depends strongly on the NO x level, with acidic products formed under high-NO x conditions only. We present, to our knowledge, the first evidence of particle-phase esterification reactions in SOA, where the further oxidation of the isoprene oxidation product methacrolein under high-NO x conditions produces polyesters involving 2-methylglyceric acid as a key monomeric unit. These oligomers comprise ∼22-34% of the high-NO x SOA mass. Under low-NO x conditions, organic peroxides contribute significantly to the low-NO x SOA mass (∼61% when SOA forms by nucleation and ∼25-30% in the presence of seed particles). The contribution of organic peroxides in the SOA decreases with time, indicating photochemical aging. Hemiacetal dimers are found to form from C 5 alkene triols and 2-methyltetrols under low-NO x conditions; these compounds are also found in aerosol collected from the Amazonian rainforest, demonstrating the atmospheric relevance of these low-NO x chamber experiments.