Atmospheric photooxidation of alkylbenzenes—II. Evidence of formation of epoxide intermediates

Wang, Yuchen; Jeffries, Harvey E.

doi:10.1016/s1352-2310(97)88637-2

Cited by 94 publications

(97 citation statements)

References 8 publications

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“…1, the epoxy-oxy intermediate may be formed from the further rearrangement of the peroxidebicyclic intermediate discussed above. This route is based on the qualitative observations of Yu and Jeffries (1997) and Kwok et al (1997), and is included to represent the balance of the OH-initiated chemistry not accounted for by the routes discussed above. Consistent with the rules presented previously Saunders et al, 2003) for oxy radicals containing a β-hydroxy group, the epoxy-oxy radical undergoes ringopening, followed by reaction with O 2 to generate HO 2 and a representative epoxydicarbonylene product.…”

Section: Ro 2 Radicals From H-abstractionmentioning

confidence: 99%

“…4.5.3) the epoxy-oxy route leading to the generation of representative epoxydicarbonylene products was included to account for the balance of the OHinitiated reaction of the aromatic hydrocarbons not accounted for by the other routes. Although such epoxy products have been detected (Yu and Jeffries, 1997), their yields have not been quantified and there is little information on their degradation chemistry. Because of their multifunctional structure, initiation reactions with OH, O 3 , NO 3 and direct photolysis are treated in MCM v3.…”

Section: Epoxydicarbonylenesmentioning

confidence: 99%

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Protocol for the development of the Master Chemical Mechanism, MCM v3 (Part B): tropospheric degradation of aromatic volatile organic compounds

et al. 2003

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Abstract. Kinetic and mechanistic data relevant to the tropospheric degradation of aromatic volatile organic compounds (VOC) have been used to define a mechanism development protocol, which has been used to construct degradation schemes for 18 aromatic VOC as part of version 3 of the Master Chemical Mechanism (MCM v3). This is complementary to the treatment of 107 non-aromatic VOC, presented in a companion paper. The protocol is divided into a series of subsections describing initiation reactions, the degradation chemistry to first generation products via a number of competitive routes, and the further degradation of first and subsequent generation products. Emphasis is placed on describing where the treatment differs from that applied to the non-aromatic VOC. The protocol is based on work available in the open literature up to the beginning of 2001, and some other studies known by the authors which were under review at the time. Photochemical Ozone Creation Potentials (POCP) have been calculated for the 18 aromatic VOC in MCM v3 for idealised conditions appropriate to north-west Europe, using a photochemical trajectory model. The POCP values provide a measure of the relative ozone forming abilities of the VOC. These show distinct differences from POCP values calculated previously for the aromatics, using earlier versions of the MCM, and reasons for these differences are discussed.

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Section: Ro 2 Radicals From H-abstractionmentioning

confidence: 99%

Section: Epoxydicarbonylenesmentioning

confidence: 99%

Protocol for the development of the Master Chemical Mechanism, MCM v3 (Part B): tropospheric degradation of aromatic volatile organic compounds

et al. 2003

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“…The furanones and γ -dicarbonyl compounds are proposed co-products of glyoxal and methylglyoxal formed as primary products from the decomposition of a peroxide-bicyclic radical, and maleic anhydride and citraconic anhydride are formed in the oxidation of the γ -dicarbonyl compounds. Epoxy-type products have also been proposed as aromatic oxidation products, and support for their formation has been provided by GC-MS experiments (Yu and Jeffries, 1997). However, positive confirmation and quantification of these products requires standards and has not yet been achieved.…”

Section: Experimental Designmentioning

confidence: 99%

Measurements of photo-oxidation products from the reaction of a series of alkyl-benzenes with hydroxyl radicals during EXACT using comprehensive gas chromatography

et al. 2003

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Abstract. Photo-oxidation products from the reaction of a series of alkyl-benzenes, (benzene, toluene, p-xylene and 1,3,5-trimethyl-benzene) with hydroxyl radicals in the presence of NO x have been investigated using comprehensive gas chromatography (GC×GC). A GC×GC system has been developed which utilises valve modulation and independent separations as a function of both volatility and polarity. A number of carbonyl-type compounds were identified during a series of reactions carried out at the European Photoreactor (EUPHORE), a large volume outdoor reaction chamber in Valencia, Spain. Experiments were carried as part of the EXACT project (Effects of the oXidation of Aromatic Compounds in the Troposphere). Two litre chamber air samples were cryo-focused, with a sampling frequency of 30 minutes, allowing the evolution of species to be followed over oxidation periods of 3-6 hours. To facilitate product identification, several carbonyl compounds, which were possible products of the photo-oxidation, were synthesised and used as reference standards.For toluene reactions, observed oxygenated intermediates found included the co-eluting pair α-angelicalactone/4-oxo-2-pentenal, maleic anhydride, citraconic anhydride, benzaldehyde and p-methyl benzoquinone. In the p-xylene experiment, the products identified were E/Z-hex-3-en-2,5-dione and citraconic anhydride. For 1,3,5-TMB reactions, the products identified were 3,5-dimethylbenzaldehyde, 3,5-dimethyl-3H-furan-2-one and 3-methyl-5-methylene-5H-furan-2-one. Preliminary quantification was carried out on identified compounds using liquid standards. Comparison of FTIR and GC×GC for the measurement of the parent aroCorrespondence to: J. F. Hamilton (jacquih@chemistry.leeds.ac.uk) matics generally showed good agreement. Comparison of the concentrations observed by GC×GC to concentrationtime profiles simulated using the Master Chemical Mechanism, MCMv3, demonstrates that this mechanism significantly over-predicts the concentrations of many product compounds and highlights the uncertainties which exist in our understanding of the atmospheric oxidation of aromatics.

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“…Advances in understanding have led to the construction of new degradation schemes incorporating additional reactions describing the initial stages of oxidation and the further degradation of the products formed after ring opening. [26][27][28][29] The updated schemes for the aromatic hydrocarbons alone have added 3000 chemical reactions to the MCM V2.0. However, because this work on the degradation mechanisms of the aromatic hydrocarbons is still far from complete, we have not pursued the characterization of the reactivities of aromatic hydrocarbons in this initial study using MCM V2.0.…”

Section: Master Chemical Mechanismmentioning

confidence: 99%

Characterization of the Reactivities of Volatile Organic Compounds Using a Master Chemical Mechanism

Derwent

Jenkin

Saunders³

et al. 2001

Journal of the Air & Waste Management Association

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IMPLICATIONSThe purpose of this paper is to demonstrate that it is possible to derive a reactivity scale using a detailed master chemical mechanism. It is shown that the reactivity scale obtained by this approach is quantitatively consistent with the most widely accepted urban reactivity scale. The good agreement found between the two reactivity scales should give added confidence to policy-makers in formulating cost-effective strategies for the control of the emissions of organic compounds based on the reactivity concept. ABSTRACTA comprehensive description of the ozone-forming potentials of 101 organic compounds has been constructed under North American urban "averaged conditions" using a detailed master chemical mechanism and a simple air parcel trajectory model. This chemical mechanism describes the reactions of 3603 chemical species taking part in more than 10,500 chemical reactions. An index value has been calculated for each organic compound, which describes the increment in ozone concentrations found downwind of an urban area following the emission of a fixed increment in the mass emission of each organic compound. These indices, termed photochemical ozone creation potentials (POCPs), have been expressed on a scale relative to ethylene (ethene) = 100, and a reactivity scale has been generated for alkanes, alkenes, and oxygenated and halogenated organic compounds. A high degree of correlation (R 2 = 0.9) was found between these POCP values and the most widely accepted urban reactivity scale. While the reactivities of most of the 86 organic compounds compared fell within a consistent range, significant discrepancies were found for only 5 compounds.Single-day or multiday conditions appear to be important in establishing quantitative reactivity scales for the less reactive organic compounds.

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Atmospheric photooxidation of alkylbenzenes—II. Evidence of formation of epoxide intermediates

Cited by 94 publications

References 8 publications

Protocol for the development of the Master Chemical Mechanism, MCM v3 (Part B): tropospheric degradation of aromatic volatile organic compounds

Protocol for the development of the Master Chemical Mechanism, MCM v3 (Part B): tropospheric degradation of aromatic volatile organic compounds

Measurements of photo-oxidation products from the reaction of a series of alkyl-benzenes with hydroxyl radicals during EXACT using comprehensive gas chromatography

Characterization of the Reactivities of Volatile Organic Compounds Using a Master Chemical Mechanism

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