Atmospheric reactions of alkoxy and ?-hydroxyalkoxy radicals

Atkinson, Roger

doi:10.1002/(sici)1097-4601(1997)29:2<99::aid-kin3>3.0.co;2-f

Cited by 298 publications

(509 citation statements)

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“…Available experimental information for alkoxy and β-hydroxyalkoxy radicals (which have particular relevance to VOC degradation) has been reviewed by Atkinson (1997b), and experimental studies for a number other classes of substituted oxy radical have been reported. In the absence of such data, the fates of oxy radicals in the MCM are generally defined by analogy, as described previously and updated below.…”

Section: Reactions Of Oxy Radical Intermediatessupporting

confidence: 53%

“…In the absence of such data, the fates of oxy radicals in the MCM are generally defined by analogy, as described previously and updated below. Atkinson (1997b) described an approach for estimating rate coefficients for atmospheric reactions of alkoxy and β-hydroxyalkoxy radicals. The expressions recommended for the reactions of primary and secondary alkoxy radicals with O 2 (reaction type 21) are used as generic rate coefficients for all oxy radical types in MCM v3.…”

Section: Reactions Of Oxy Radical Intermediatesmentioning

confidence: 99%

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

et al. 2003

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Abstract. Kinetic and mechanistic data relevant to the tropospheric degradation of volatile organic compounds (VOC), and the production of secondary pollutants, have previously been used to define a protocol which underpinned the construction of a near-explicit Master Chemical Mechanism. In this paper, an update to the previous protocol is presented, which has been used to define degradation schemes for 107 non-aromatic VOC as part of version 3 of the Master Chemical Mechanism (MCM v3). The treatment of 18 aromatic VOC is described in a companion paper. The protocol is divided into a series of subsections describing initiation reactions, the reactions of the radical intermediates and the further degradation of first and subsequent generation products. Emphasis is placed on updating the previous information, and outlining the methodology which is specifically applicable to VOC not considered previously (e.g., α-and β-pinene). The present protocol aims to take into consideration 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. Application of MCM v3 in appropriate box models indicates that the representation of isoprene degradation provides a good description of the speciated distribution of oxygenated organic products observed in reported field studies where isoprene was the dominant emitted hydrocarbon, and that the α-pinene degradation chemistry provides a good description of the time dependence of key gas phase species in α-pinene/NO X photo-oxidation experiments carried out in the European Photoreactor (EU-PHORE). Photochemical Ozone Creation Potentials (POCP) have been calculated for the 106 non-aromatic non-methane 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. Where applicable, the values are compared with those calculated with previous versions of the MCM.

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Section: Reactions Of Oxy Radical Intermediatessupporting

confidence: 53%

Section: Reactions Of Oxy Radical Intermediatesmentioning

confidence: 99%

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

et al. 2003

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“…The hydroxyalkyl radical reacts rapidly with O 2 in the FAGE detection cell, leading to the production of a carbonyl compound and HO 2 . However, the ability of large alkoxy radicals to rapidly isomerize and decompose (Atkinson, 1997;Finlayson-Pitts and Pitts Jr., 2000) also results in a rapid production of HO 2 radicals and a larger conversion efficiency.…”

Section: Resultsmentioning

confidence: 99%

Measurement of interferences associated with the detection of the hydroperoxy radical in the atmosphere using laser-induced fluorescence

2018

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Abstract.One technique used to measure concentrations of the hydroperoxy radical (HO 2 ) in the atmosphere involves chemically converting it to OH by addition of NO and subsequent detection of OH. However, some organic peroxy radicals (RO 2 ) can also be rapidly converted to HO 2 (and subsequently OH) in the presence of NO, interfering with measurements of ambient HO 2 radical concentrations. This interference must be characterized for each instrument to determine to what extent various RO 2 radicals interfere with measurements of HO 2 and to assess the impact of this interference on past measurements. The efficiency of RO 2 -to-HO 2 conversion for the Indiana University laser-induced fluorescencefluorescence assay by gas expansion (IU-FAGE) instrument was measured for a variety of RO 2 radicals. Known quantities of OH and HO 2 radicals were produced from the photolysis of water vapor at 184.9 nm, and RO 2 radicals were produced by the reaction of several volatile organic compounds (VOCs) with OH. The conversion efficiency of RO 2 radicals to HO 2 was measured when NO was added to the sampling cell for conditions employed during several previous field campaigns. For these conditions, approximately 80 % of alkene-derived RO 2 radicals and 20 % of alkane-derived RO 2 radicals were converted to HO 2 . Based on these measurements, interferences from various RO 2 radicals contributed to approximately 35 % of the measured HO 2 signal during the Mexico City Metropolitan Area (MCMA) 2006 campaign (MCMA-2006), where the measured VOCs consisted of a mixture of saturated and unsaturated species. However, this interference can contribute more significantly to the measured HO 2 signal in forested environments dominated by unsaturated biogenic emissions such as isoprene.

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“…The formaldehyde formation is proposed to result from the decomposition of R5 into a carbonyl compound and a methyl radical, the latter rapidly reacting with 0 2 and NO to produce formaldehyde. Such methyl group elimination has been observed with other alkoxy radicals [Atkinson, 1996, and references therein]. A similar decomposition of the/3-nitroso alkoxy radical analog to R5 has also been proposed in the reaction mechanism of a-pinene with NO 3 radicals [Wangberg et al, 1997].…”

Section: Reaction Of T•-pinene Withmentioning

confidence: 99%

Product study and mechanisms of the reactions of α‐pinene and of pinonaldehyde with OH radicals

Nozière¹,

Barnes²,

Becker³

1999

J. Geophys. Res.

176

192

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Abstract. The reactions of a-pinene and of its main oxidation product, pinonaldehyde (3-acetyl-2,2-dimethyl-cyclobutyl-ethanal), with OH radicals have been studied in the laboratory using Fourier transform infrared spectroscopy for real-time monitoring of the gas-phase chemical species and a Scanning Mobility Particle Sizer system (3071 A, TSI) for the study of the secondary aerosol formation. All gas-phase molar yields were quantified using calibrated reference of the pure compound, except for the nitrates products. The results were: for the a-pinene experiments in the presence of NOx, pinonaldehyde, (87 _ 20)%; total nitrates (18 _+ 9)%; formaldehyde, (23 +_ 9)%; acetone (9 _ 6)%; for the a-pinene experiments in the absence of NOx: pinonaldehyde, (37 _+ 7)%; formaldehyde, (8 _ 1)%; acetone, (7 _+ 2)%; for the pinonaldehyde experiments in the presence of NO, formaldehyde (152 _ 56)% and acetone (15 _+ 7)%. The aerosol measurements showed that the condensed products accounted for the missing carbon in the gas-phase balance. The partitioning of the products into the condensed phase was found to be potentially .significant under experimental conditions but less than 10% for initial a-pinene concentrations lower than 1013 molecule cm -3 and hence negligible under atmospheric conditions in the absence of aerosol seeds. On the basis of these results a comprehensive mechanism for the gas-phase reaction of a-pinene with OH in the presence of NOx has been proposed, including quantitative values for all the involved branching ratios. al., 1998], have been studied in laboratory. These studies have generally focused on the first oxidation step and only a few products have been quantified. Pinonaldehyde (3-acetyl-2,2-dimethyl-cyclobutyl-ethanal) was found to be the main product but has never been quantified on an absolute basis by means of a calibrated sample of the pure compound. The only other reaction product identified and quantified is acetone. Moreover, most of the studies have not taken into account the condensed products formed by these reactions, which may represent a significant fraction of the carbon balance under laboratory conditions as it will be shown in the present work. As a result, the understanding of the mechanism for the reaction of a-pinene with OH radicals remained difficult. Furthermore, secondary oxidation steps such as the further reactions of pinonaldehyde, which are important to assess the overall effect of a-pinene on tropospheric chemistry, have never been studied.In the present work, the mechanism of the reaction of a-pinene with OH radicals has been studied. Several gas-phase products such as pinonaldehyde, alkyl nitrates, acetone, and formaldehyde, have been identified and, except for the alkyInitrates, quantified using calibrated reference samples. This work also gives a first insight into the oxidation mechanism beyond the initial oxidation step by studying the reaction of pinonaldehyde with OH radicals. A quantification of the condensed products formed in these reactions has been performe...

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Atmospheric reactions of alkoxy and ?-hydroxyalkoxy radicals

Cited by 298 publications

References 47 publications

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

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

Measurement of interferences associated with the detection of the hydroperoxy radical in the atmosphere using laser-induced fluorescence

Product study and mechanisms of the reactions of α‐pinene and of pinonaldehyde with OH radicals

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