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  1. Carter WPL and Atkinson R (1985). "Atmospheric chemistry of alkanes." JOURNAL OF ATMOSPHERIC CHEMISTRY 3: 377-405.
  2. SHEPSON PB, EDNEY EO, et al. (1985). "THE PRODUCTION OF ORGANIC NITRATES FROM HYDROXYL AND NITRATE RADICAL REACTION WITH PROPYLENE." ENVIRONMENTAL SCIENCE & TECHNOLOGY 19(9): 849-854.
  3. Atkinson R (1987). "A structure-activity relationship for the estimation of rate constants for the gas-phase reactions of the OH radicals with organic-compounds." INTERNATIONAL JOURNAL OF CHEMICAL KINETICS 19(9): 799-828.
  4. CARTER WPL and ATKINSON R (1989). "ALKYL NITRATE FORMATION FROM THE ATMOSPHERIC PHOTOOXIDATION OF ALKANES - A REVISED ESTIMATION METHOD." JOURNAL OF ATMOSPHERIC CHEMISTRY 8(2): 165-173.
  5. Dagaut P, Liu RZ, et al. (1989). "Kinetic measurements of the gas-phase reactions of OH radicals with hydroxy ethers, hydroxy ketones and keto ethers." JOURNAL OF PHYSICAL CHEMISTRY 93(23): 7838-7840.
  6. Atkinson R (1989). "Kinetics and mechanisms of the gas-phase reactions of the hydroxyl radical with organic compounds." JOURNAL OF PHYSICAL AND CHEMICAL REFERENCE DATA Monograph 1.
  7. ATKINSON R (1990). "GAS-PHASE TROPOSPHERIC CHEMISTRY OF ORGANIC-COMPOUNDS - A REVIEW." ATMOSPHERIC ENVIRONMENT PART A-GENERAL TOPICS 24(1): 1-41.
  8. LIGHTFOOT PD, COX RA, et al. (1992). "ORGANIC PEROXY-RADICALS - KINETICS, SPECTROSCOPY AND TROPOSPHERIC CHEMISTRY." ATMOSPHERIC ENVIRONMENT PART A-GENERAL TOPICS 26(10): 1805-1961.
    ABSTRACT
    The present state of knowledge of organic, or carbon-based, peroxy radicals (RO2) is reviewed. Data on the chemical and physical properties of peroxy radicals in the gas-phase is considered, as well as the role of peroxy radicals in tropospheric chemistry and measurements of their concentrations in the atmosphere. Where appropriate, peroxy radicals are grouped together by type (alkyl, acyl, oxygen-substituted, halogen-substituted and aromatic radicals) to facilitate comparison. Data on the hydroperoxy radical (HO2) is included where it is directly relevant to measurements on organic peroxy radicals, eg. absorption cross-sections used in measurements of RO2 + HO2 rate constants. The literature data is critically reviewed and recommendations for absorption cross-sections, rate constants and branching ratios are made where considered appropriate. The laboratory experimental techniques which have been used for the generation and detection of peroxy radicals and the products of their reactions are discussed. The structure, spectroscopy and thermochemistry of the radicals are examined. Although the majority of spectroscopic data concerns the u.v. spectra much used for kinetic studies, near-infrared, infrared and electron spin resonance spectra are also considered. In many cases, peroxy radical u.v. spectra are well-fitted by a Gaussian distribution function, enabling the cross-sections to be easily calculated at any wavelength. For the purpose of this review, the chemical reactions of peroxy radicals am divided into reactions with organic peroxy radicals with HO2, with NO and NO2, and finally with other species. Peroxy radical abstraction and addition reactions with closed-shell species are sufficiently slow to be of negligible importance at temperatures pertinent to the atmosphere and are consequently not covered. Data on both the kinetics and mechanisms of peroxy radical reactions are considered. The role of peroxy radicals as intermediates in the atmospheric degradation of volatile organic compounds and in the production of ozone in the troposphere under both low and high [NOx] conditions is discussed. The involvement of peroxy radicals in night-time oxidation chemistry and the oxidation of halocarbons is also indicated. The techniques used for the difficult measurement of peroxy radical concentrations in the atmosphere are described, together with the results to date. Finally, some tentative suggestions as to further avenues of research are made, based on the data reviewed here and with particular reference to the solution of outstanding problems in atmospheric chemistry. Although a great deal of progress has been made in recent years, it is clear that additional work is needed in most areas covered by this review. New, sensitive and selective laboratory techniques are required for studies of peroxy radical kinetics and high level ab initio calculations would help design laser-based detection techniques. Further product studies of photooxidation systems are needed, particularly as a function of temperature. Recent work has shown that the rate constants for RO2 + HO2 reactions used in modelling studies may be too low; if so, these reactions will be correspondingly more important than previously believed in tropospheric oxidation. Recent kinetic studies of the potentially important reactions of methylperoxy radicals with ClO and NO3 need to be confirmed and mechanistic work is necessary. Although substantial progress has been made toward the monitoring of peroxy radical concentrations in the atmosphere, more work is needed, both on measurements and the development of new techniques.

  9. WALLINGTON TJ, DAGAUT P, et al. (1992). "ULTRAVIOLET-ABSORPTION CROSS-SECTIONS AND REACTION-KINETICS AND MECHANISMS FOR PEROXY-RADICALS IN THE GAS-PHASE." CHEMICAL REVIEWS 92(4): 667-710.
  10. MUTHURAMU K, SHEPSON PB, et al. (1993). "PREPARATION, ANALYSIS, AND ATMOSPHERIC PRODUCTION OF MULTIFUNCTIONAL ORGANIC NITRATES." ENVIRONMENTAL SCIENCE & TECHNOLOGY 27(6): 1117-1124.
    ABSTRACT
    Ambient measurements of multifunctional organic nitrates have become necessary to understand the complete tropospheric NO(y) budget. Laboratory studies indicate that multifunctional organic nitrates that are produced from OH and NO3 reaction with alkenes may be important; however, they have yet to be detected in atmospheric samples. We have synthesized several C3-C6 alkyl nitrates, alpha,beta-hydroxynitrates, and dinitrates that are produced from oxidation of atmospheric hydrocarbons. In this paper we report on procedures for their synthesis and purification, and on results of structural characterization by H-1 NMR and mass spectrometry. All organic nitrates were found to be stable on charcoal adsorbent (often used for sampling) for periods of weeks. Although good chromatographic separation is possible, we find that there may be serious problems with irreversible adsorption on column or injection port surfaces that may interfere with quantitative measurement. However, when the columns are properly conditioned, reproducible analyses can be conducted. We report the relative ECD response for all compounds for different injection systems. We have determined the yield of 2-nitrooxy-3-hydroxybutane formation from OH reaction with cis-2-butene (in the presence of NO) to be 0.037 +/- 0.009. The possible causes, including column conditioning, of the elusive nature of the hydroxynitrates and dinitrates in GC/ECD chromatographic analyses of ambient air samples are discussed.

  11. Peeters J, Boullart W, et al. (1994). "Site-specific partial rate constants for OH addition to alkenes and dienes." Proceedings of the EUROTRAC Symposium '94, Garmisch-Partenkirchen, FRG, April 1994: 110-114.
  12. Atkinson R (1994). "Gas-phase tropospheric chemistry of organic compounds." JOURNAL OF PHYSICAL AND CHEMICAL REFERENCE DATA Monograph 2: 1-216.
    ABSTRACT
    The gas-phase reactions of selected classes of organic compounds (alkanes, alkenes (including isoprene and monoterpenes), alkynes, aromatic hydrocarbons and oxygen-containing organic compounds and their degradation products) under tropospheric conditions are reviewed and evaluated. The recommendations of the most recent IUPAC evaluation [J. Phys. Chem. Ref. Data 21, 1125 (1992)] are used for the less-than-or-equal-to C3 organic compounds, unless more recent data necessitates reevaluation. In addition to the review of the gas-phase tropospheric chemistry of these classes of organic compounds, the previous reviews and evaluations of Atkinson [J. Phys. Chem. Ref Data, Monograph 1 (1989)] for OH radical reactions, Atkinson [J. Phys. Chem. Ref. Data 20, 459 (1991)] for NO3 radical reactions and Atkinson and Carter [Chem. Rev. 84, 437 (1984)] for O3 reactions with organic compounds are updated.

  13. Hoffman A, Mors V, et al. (1995). "Time resolved studies of oxidation mechanisms of hydrocarbons under tropospheric conditions." LACTOZ/HALIPP Workshop, Leipzig, September 1995, CEC Air Pollution Research Report.
  14. EBERHARD J, MULLER C, et al. (1995). "ISOMERIZATION OF ALKOXY RADICALS UNDER ATMOSPHERIC CONDITIONS." ENVIRONMENTAL SCIENCE & TECHNOLOGY 29(1): 232-241.
    ABSTRACT
    The reactions of the 2-hexoxy radical and the 3-hexoxy radical have been studied in a collapsible Teflon bag reactor under conditions relevant to the atmosphere. The alkoxy radicals were generated either by the photolysis of the corresponding hexyl nitrite or by the OH radical initiated photooxidation of hexane. The hexoxy radicals were chosen as model species to examine the importance of alkoxy radical isomerization versus unimolecular decomposition or reaction with oxygen. The fraction of 2-hexoxy radicals undergoing isomerization was determined directly from the analysis of the 5-hydroxyhexan-2-one product. The fraction of 3-hexoxy radicals undergoing isomerization could only be determined indirectly. The formation of products proposed to be generated from the isomerization reaction channels was observed for the first time, including 5-nitrooxyhexan-2-ol from the reaction of isomerized radicals with NO. The approximate quantitative results confirm the predicted dominance of isomerization (greater than or equal to 68%) over other reaction pathways for longer chain alkoxy radicals. The results are compared with predictions based on kinetic estimations.

  15. CARTER WPL (1995). "COMPUTER MODELING OF ENVIRONMENTAL CHAMBER MEASUREMENTS OF MAXIMUM INCREMENTAL REACTIVITIES OF VOLATILE ORGANIC-COMPOUNDS." ATMOSPHERIC ENVIRONMENT 29(18): 2513-2527.
    ABSTRACT
    A detailed atmospheric photochemical mechanism which had been previously used in model calculations for developing ozone reactivity scales for volatile organic compounds (VOCs) was evaluated by comparing its predictions with measurements of incremental reactivities in an environmental chamber system. An updated version of this mechanism is also described and evaluated. The experiments consisted of determining the effects of adding representative alkanes, alkenes, aromatic hydrocarbons, aldehydes or CO on NO oxidation, ozone formation and radical levels in a simplified model photochemical smog system representing conditions where ozone formation is most sensitive to VOCs. The published mechanism correctly simulated the observed qualitative reactivity trends, but overpredicted the effect of adding formaldehyde early in the experiments, performed poorly in simulating reactivities of branched alkanes, tended to underpredict the reactivities of alkenes, and did not simulate differences in reactivities of aromatic isomers. The updates to the mechanism improved the simulationresults for the branched alkanes and the alkenes, but not for formaldehyde and the aromatics. The implications of these results concerning the development of atmospheric mechanisms for VOCs are discussed.

  16. Kwok ESC and Atkinson R (1995). "Estimation of hydroxyl radical reaction-rate constants for gas-phase organic-compounds using a structure-reactivity relationship - an update." ATMOSPHERIC ENVIRONMENT 29(14): 1685-1695.
    ABSTRACT
    The structure-reactivity approach proposed by Atkinson (1986, Chem. Rev. 86, 69-201) and extended by Atkinson (1987, Int. J. Chern. Kinet. 19, 799-828) for the calculation of rate constants for the gas-phase reactions of the OH radical with organic compounds has been re-investigated using the presently available database. Substituent group factors for several new groups are derived, including those for fluorinated ethers. Using a large fraction of the available database to derive the parameters needed to calculate the OH radical reaction rate constants, the 298 K rate constants of similar to 90% of approximately 485 organic compounds are predicted to within a factor of 2 of the experimental values. Disagreements between calculated and experimental rate constants most commonly occur for halogen-containing compounds, and in particular for haloalkanes, haloalkenes and halogenated ethers. Disagreements also arise for ethers, especially for polyethers and cycloethers. The present estimation technique is reasonably reliable when used within the database used in its derivation, but extrapolation to organic compounds outside of this database results in a lack of assurance of its reliability, and its use for organic compounds which belong to classes other than those used in its development is discouraged.

  17. Villalta PW and Howard CJ (1996). "Direct kinetics study of the CH3C(O)O-2+NO reaction using chemical ionization mass spectrometry." JOURNAL OF PHYSICAL CHEMISTRY 100(32): 13624-13628.
    ABSTRACT
    A direct measurement of the CH3C(O)O-2 + NO gas-phase reaction rate coefficient over the temperature range 200-402 K was made using chemical ionization mass spectrometric detection of the CH3C(O)O-2 reactant. A significant temperature dependence was observed, and a temperature dependent expression of k(T) = (8.1 +/- 1.3) x 10(-12) exp{(270 +/- 60)/T} cm(3) molecule(-1) s(-1) was determined. The 298 K rate coefficient, k = (2.0 +/- 0.3) x 10(-11) cm(3) molecule(-1) s(-1), agrees well with results from previous indirect measurements. NO2, CH3, and CO2 were positively identified as products originating from the reaction. The question of whether CH3 and CO2 are direct products of the reaction or result from the thermal decomposition of CH3C(O)O could not be answered, The 298 K rate coefficients for the reactions of SF6-, I-, and O-3(-) with CH3C(O)O-2 were measured to be (7(-2)(+4)) x 10(-10), (9(-5)(+7)) x 10(-10), and greater than or equal to 2 x 10(-10) cm(3) molecule(-1) s(-1), respectively.

  18. Eberhard J and Howard CJ (1996). "Temperature-dependent kinetics studies of the reactions of C2H5O2 and n-C3H7O2 radicals with NO." INTERNATIONAL JOURNAL OF CHEMICAL KINETICS 28(10): 731-740.
    ABSTRACT
    The rate coefficients for the gas-phase reactions of C2H5O2 and n-C3H7O2 radicals with NO have been measured over the temperature range of (201-403) K using chemical ionization mass spectrometric detection of the peroxy radical, The alkyl peroxy radicals were generated by reacting alkyl radicals with O-2, where the alkyl radicals were produced through the pyrolysis of a larger alkyl nitrite. In some cases C2H5 radicals were generated through the dissociation of iodoethane in a low-power radio Frequency discharge. The discharge source was also tested for the i-C3H7O2 + NO reaction, yielding k(298 K) = (9.1 +/- 1.5) x 10(-12) cm(3) molecule(-1) s(-1), in excellent agreement with our previous determination. The temperature dependent rate coefficients were found to be k(T) = (2.6 +/- 0.4) x 10(-12) exp{(380 +/- 70)/T} cm(3) molecule(-1) s(-1) and = 12.9 +/- 0.5) x 10(-12) exp{(350 +/- 60)T} cm(3) molecule(-1) s(-1) for the reactions of C2H5O2 and n-C3H7O2 radicals with NO, respectively. The rate coefficients at 298 K derived from these Arrhenius expressions are k = (9.3 +/- 1.6) x 10(-12) cm(3) molecule(-1) s(-1) for C2H5O2 radicals and k = (9.4 +/- 1.6) x 10(-12) cm(3) molecule(-1) s(-1) for n-C2H5O2 radicals. (C) 1996 John Wiley & Sons, Inc.

  19. Eberhard J, Villalta PW, et al. (1997). "Reaction of iso-propyl peroxy radicals with NO over the temperature range 201-401 K." JOURNAL OF PHYSICAL CHEMISTRY 100(3): 993-997.
  20. Wallington TJ, Nielsen OJ, et al. (1997). "Reactions of organic peroxy radicals in the gas phase." in "Peroxy Radicals" (Ed) Alfassi Z., John Wiley and Sons, 1997.
  21. Eberhard J and Howard CJ (1997). "Rate coefficients for the reactions of some C-3 to C-5 hydrocarbon peroxy radicals with NO." JOURNAL OF PHYSICAL CHEMISTRY A 101(18): 3360-3366.
    ABSTRACT
    The rate coefficients for the gas-phase reactions of allyl-, tert-, butyl-, cyclopentyl-, and 2-pentylperoxy radicals with NO have been measured at 297 +/- 2 K in a flow tube reactor using chemical ionization mass spectrometric (CIMS) detection of the peroxy radical. The hydrocarbon radicals were produced through the dissociation of the parent alkyl iodide in a low-power radio frequency (rf) discharge. The unimolecular decomposition of the c-pentyl radicals in the rf discharge yielded allyl radicals, The peroxy radicals were generated by reacting the hydrocarbon radicals with O-2. The rate coefficients were found to be, in units of 10(-12) cm(3) molecule(-1) s(-1), 10.5 +/- 1.8, 7.9 +/- 1.3, 10.9 +/- 1.9, and 8.0 +/- 1.4 for the reactions of NO with CH2=CHCH2O2, t-C4H9O2, C-C5H9O2, and 2-C5H11O2 radicals, respectively. The results of this study together with our previous results for nonsubstituted C-1-C-3 alkyl peroxy radicals suggest no significant trend in the rate coefficients with size and branching of the radicals, This is in contradiction to some previous studies, which found that the rate coefficients decrease with increasing radical size and complexity. Some implications of this finding for atmospheric chemistry are briefly discussed.

  22. Porter E, Wenger J, et al. (1997). "Kinetic studies on the reactions of hydroxyl radicals with diethers and hydroxyethers." JOURNAL OF PHYSICAL CHEMISTRY A 101(32): 5770-5775.
    ABSTRACT
    Rate constants for the reactions of OH radicals with a series of diethers and hydroxyethers have been determined at 298 +/- 2 K. Rate measurements were made using a pulsed laser photolysis resonance fluorescence technique at total pressures of similar to 100 Torr and a conventional photolytic relative rate method at atmospheric pressure. The temperature dependencies of the rate constants for four diethers were also studied over the temperature range 230-372 K using pulsed laser photolysis resonance fluorescence. The rate data for reaction of OH with the diethers show significant deviations from simple structure-activity relationships. Evidence is presented that suggests that these deviations may be a consequence of stabilization of the reaction transition states by hydrogen bonding.

  23. Atkinson R (1997). "Gas-phase tropospheric chemistry of volatile organic compounds.1. Alkanes and alkenes." JOURNAL OF PHYSICAL AND CHEMICAL REFERENCE DATA 26(2): 215-290.
    ABSTRACT
    Literature data (through mid-1996) concerning the gas-phase reactions of alkanes and alkenes (including isoprene and monoterpenes) leading to their first generation products are reviewed and evaluated for tropospheric conditions. The recommendations of the most recent IUPAC evaluation [J. Phys. Chem. Ref. Data, 26, No. 3 (1997)] are used for the less than or equal to C-3 organic compounds, unless more recent data necessitates reevaluation. The most recent review and evaluation of Atkinson [J. Phys. Chem. Ref. Data, Monograph 2, 1 (1994)] concerning the kinetics of the reactions of OH radicals, NO3 radicals, and O-3 is also updated for these two classes of volatile organic compounds. (C) 1997 American Institute of Physics and American Chemical Society.

  24. Jenkin ME and Hayman. GD. (1999). "Photochemical ozone creation potentials for oxygenated volatile organic compounds: sensitivity to variations in kinetic and mechanistic parameters." ATMOSPHERIC ENVIRONMENT 33(8): 1275-1293.
    ABSTRACT
    The sensitivity of Photochemical Ozone Creation Potentials (POCP) to a series of systematic variations in the rates and products of reactions of radical intermediates and oxygenated products is investigated for the C-4 alcohols, l-butanol (II-butanol) and 2-methyl-1-propanol (i-butanol), using the recently developed Master Chemical Mechanism (MCM) as the base case. The POCP values are determined from the calculated formation of ozone in the boundary layer over a period of approximately five days along an idealised straight line trajectory, using a photochemical trajectory model and methodology described in detail previously. The results allow the relative impacts on calculated ozone formation of various classes of chemical reaction within the degradation chemistry to be assessed. The calculated POCP is found to be very insensitive to many of the changes investigated. However, it is found to be sensitive to variations in the rate coefficient for the initiating reaction with OH (k(OH)), although the sensitivity decreases with increasing k(OH). The POCP appears to vary approximately linearly with k(OH) at low values (i.e. k(OH) less than ca. 4 x 10(-13) cm(3) molecule(-1) s(-1)), whereas at high reactivities (i.e, k(OH) greater than ca. 4 x 10(-11) cm(3) molecule(-1) s(-1)), the calculated POCP value is comparatively insensitive to the precise value of k(OH). The POCP is also very sensitive to mechanistic changes which influence the yields of unreactive oxygenated products (i.e. those with OH reactivities below ca. 10(-12) cm(3) molecule(-1) s(-1)), for example acetone. The propensity of the organic compound to produce organic nitrates (which act as comparatively unreactive reservoirs for free radicals and NOx) also appears to have a notable influence on the calculated POCP. Recently reported information relevant to the degradation of oxygenated VOCs is then used to update the chemical schemes for the 17 alcohols and glycols, 10 ethers and glycol ethers, and 8 esters included in the MCM, and new schemes are incorporated for dimethoxy methane (CH3OCH2OCH3) and dimethyl carbonate (CH3OC(O)OCH3), which are proposed fuel additives. New or updated POCP values are calculated for all 37 oxygenated VOCs and, where applicable, these are compared with the previous POCP values and reported Maximum Incremental Reactivity (MIR) values. (C) 1999 Published by Elsevier Science Ltd. All rights reserved.

  25. Atkinson R, Baulch DL, et al. (1999). "Evaluated kinetic and photochemical data for atmospheric chemistry, organic species: Supplement VII." JOURNAL OF PHYSICAL AND CHEMICAL REFERENCE DATA 28(2): 191-393.
    ABSTRACT
    This paper updates and extends part of the previous data base of critical evaluations of the kinetics and photochemistry of gas-phase chemical reactions of neutral species involved in atmospheric chemistry [J, Phys, Chem. Ref. Data 9, 295 (1980); 11, 327 (1982); 13, 1259 (1984); 1.8, 881 (1989); 21, 1125 (1992); 26, 521 (1997); 26, 1329 (1997)], The present evaluation is limited to the organic family of atmospherically important reactions. The work has been carried out by the authors under the auspices of the IUPAC Subcommittee on Gas Phase Kinetic Data Evaluation for Atmospheric Chemistry. Data sheets have been prepared for 171 thermal and photochemical reactions, containing summaries of the available experimental data with notes giving details of the experimental procedures. For each thermal reaction, a preferred value of the rate coefficient at 298 K is given together with a temperature dependence where possible. The selection of the preferred value is discussed and estimates of the accuracies of the rate coefficients and temperature coefficients have been made for each reaction. For each photochemical reaction the data sheets list the preferred values of the photoabsorption cross sections and the quantum yields of the photochemical reactions together with comments on how they were selected. The data sheets are intended to provide the basic physical chemical data needed as input for calculations which model atmospheric chemistry. A table summarizing the preferred rate data is provided, together with an Appendix listing the available values of enthalpies of formation of the reactant and product species. (C) 1999 American Institute of Physics and American Chemical Society.

  26. Atkinson R (2000). "Atmospheric oxidation." Contributon to "Handbook of property estimation methods for chemicals: Environmental and health services" (Eds) Boethling RS and Mackay, D., CRC Press.
  27. Calvert JG, Atkinson R, et al. (2000). "The mechanisms of atmospheric oxidation of alkenes." Oxford University Press, New York ISBN 0-19-513177-0.
  28. Tyndall GS, R. Cox, et al. (2001). "Atmospheric chemistry of small organic peroxy radicals." JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES 106( D11): 12157-12182.
    ABSTRACT
    Global atmospheric models play a key role in international assessments of the human impact on global climate and air pollution. To increase the accuracy and facilitate comparison of results from such models. it is essential they contain up-to-date chemical mechanisms, To this end, we present an evaluation of the atmospheric chemistry of the four most abundant organic peroxy radicals: CH3O2, C2H5O2, CH3C(O)O-2, and CH3C(O)CH2O2 The literature data for the atmospheric reactions of these radicals are evaluated. In addition, the ultraviolet absorption cross sections for the above radicals and for HO2 have been evaluated. The absorption spectra were fitted to an analytical formula, which enabled published spectra to be screened objectively. Published kinetic and product data were reinterpreted, or in some case reanalyzed, using the new cross sections, leading to a self-consistent set of kinetic, mechanistic, and spectroscopic data. Product studies were also evaluated. A set of peroxy radical reaction rate coefficients and products are recommended for use in atmospheric modeling. A three-dimensional global chemical transport model (the Intermediate Model for the Global Evolution of Species, IMAGES) was run using both previously recommended rate coefficients and the current set to highlight the sensitivity of key atmospheric trace species to the peroxy radical chemistry used in the model.

  29. Wagner V, Jenkin ME, et al. (2003). "Modelling of the photooxidation of toluene: conceptual ideas for validating detailed mechanisms." ATMOSPHERIC CHEMISTRY AND PHYSICS 3: 89-106.
    ABSTRACT
    Toluene photooxidation is chosen as an example to examine how simulations of smog-chamber experiments can be used to unravel shortcomings in detailed mechanisms and to provide information on complex reaction systems that will be crucial for the design of future validation experiments. The mechanism used in this study is extracted from the Master Chemical Mechanism Version 3 (MCM v3) and has been updated with new modules for cresol and gamma-dicarbonyl chemistry. Model simulations are carried out for a toluene-NOx experiment undertaken at the European Photoreactor (EUPHORE). The comparison of the simulation with the experimental data reveals two fundamental shortcomings in the mechanism: OH production is too low by about 44%, and the ozone concentration at the end of the experiment is over-predicted by 55%. The radical budget was analysed to identify the key intermediates governing the radical transformation in the toluene system. Ring-opening products, particularly conjugated gamma-dicarbonyls, were identified as dominant radical sources in the early stages of the experiment. The analysis of the time evolution of radical production points to a missing OH source that peaks when the system reaches highest reactivity. First generation products are also of major importance for the ozone production in the system. The analysis of the radical budget suggests two options to explain the concurrent under-prediction of OH and overprediction of ozone in the model: (1) missing oxidation processes that produce or regenerate OH without or with little NO to NO2 conversion or (2) NO3 chemistry that sequesters reactive nitrogen oxides into stable nitrogen compounds and at the same time produces peroxy radicals. Sensitivity analysis was employed to identify significant contributors to ozone production and it is shown how this technique, in combination with ozone isopleth plots, can be used for the design of validation experiments.

  30. Saunders SM, Pascoe S, et al. (2003). "Development and preliminary test results of an expert system for the automatic generation of tropospheric VOC degradation mechanisms." ATMOSPHERIC ENVIRONMENT 37(13): 1723-1735.
    ABSTRACT
    The methodology and protocol used for the construction of the master chemical mechanism (MCM) has been coupled with techniques from knowledge-based systems to develop an expert system, specifically tailored for the automatic generation of tropospheric volatile organic compound (VOC) degradation schemes. To solve the problem of automatic mechanism construction processes leading to unmanageably large mechanisms for species containing more than a few carbon atoms, strategies are developed to reduce mechanism growth. To test the mechanisms generated by the expert system, some preliminary exemplar schemes have been embedded in a simple box model to provide a comparison with the complete degradation schemes available from the MCM web site. Profiles were obtained for several of the stable and radical species. Those of the parent VOC, O-3, OH, HO2 and CH3O2 are in good agreement with profiles generated using the reference MCM schemes. Other profiles exhibited a much larger disparity, notably the sum of the peroxy radicals (RO2). These disparities provide insights for refinement of the expert system rule base. (C) 2003 Elsevier Science Ltd. All rights reserved.

  31. Jenkin ME, Saunders SM, et al. (2003). "Protocol for the development of the Master Chemical Mechanism, MCM v3 (Part B): tropospheric degradation of aromatic volatile organic compounds." ATMOSPHERIC CHEMISTRY AND PHYSICS 3: 181-193.

    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.

  32. Saunders SM, Jenkin ME, et al. (2003). "Protocol for the development of the Master Chemical Mechanism, MCM v3 (Part A): tropospheric degradation of non-aromatic volatile organic compounds." ATMOSPHERIC CHEMISTRY AND PHYSICS 3: 161-180.

    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., alpha- and pinene). The present protocol aims to take into consideration work available in the open literature Lip 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 alpha-pinene degradation chemistry provides a good description of the time dependence of key gas phase species in alpha-pinene/NOX 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.

  33. GROSJEAN D, WILLIAMS EL, et al. (1993). "ATMOSPHERIC CHEMISTRY OF ISOPRENE AND OF ITS CARBONYL PRODUCTS." ENVIRONMENTAL SCIENCE & TECHNOLOGY 27(5): 830-840.
    ABSTRACT
    The carbonyl products of isoprene, methacrolein (MTA), methyl vinyl ketone (MVK), hydroxyacetaldehyde, and hydroxyacetone have been identified and their concentrations measured in experiments involving sunlight irradiations of 1 ppm organic and 200 ppb NO in purified air. The MTA/MVK yield ratio was 1.4 for isoprene. The hydroxycarbonyl/methylglyoxal yield ratio was 4.3 for MTA and was 1.9 for MVK. The peroxyacyl nitrates PAN [RC(O)OONO2, R = CH3-] and MPAN [R = CH2=C-(CH3)-] have been measured. MPAN/PAN concentration ratios were 0.65 +/- 0.04 for isoprene and 2.3 +/- 0.1 for MTA. A search for hydroxy-PAN (R = CH2OH-) as a reaction product was not conclusive. The nitrogen-containing products NO2, PAN, and MPAN accounted for 78-90% of the reacted NO. The reaction of ozone with isoprene, MTA, and MVK has been studied with excess cyclohexane added as a scavenger for OH which is formed in the ozone-organic reaction. The ozone-organic reaction rate constants were 1.02 +/- 0.05, 4.72 +/- 0.09, and 8.95 +/- 0.25 x 10(-18) cm3 molecule-1 s-1 for MTA (18 +/- 2-degrees-C), MVK (18 +/- 2-degrees-C), and isoprene (20 +/- 2-degrees-C), respectively. Carbonyl products accounted for 70-92% of the reacted organic. The MTA/MVK yield ratio from isoprene was 2.6. The results are discussed in terms of OH-organic and ozone-organic atmospheric oxidation pathways.

  34. ASCHMANN SM and ATKINSON R (1994). "FORMATION YIELDS OF METHYL VINYL KETONE AND METHACROLEIN FROM THE GAS-PHASE REACTION OF O3 WITH ISOPRENE." ENVIRONMENTAL SCIENCE & TECHNOLOGY 28(8): 1539-1542.
    ABSTRACT
    The formation yields of methyl vinyl ketone and methacrolein from the gas-phase reaction of O3 with isoprene were determined at 296 +/- 2 K and 740 Torr total pressure of air. Sufficient cyclohexane was added to the reactant mixture to scavenge >97 % of the OH radicals formed in the O3-isoprene reaction, and secondary reactions of 03 with methyl vinyl ketone and methacrolein were taken into account. The formation yields obtained were 0.159 +/- 0.013 for methyl vinyl ketone and 0.387+/- 0.030 for methacrolein. Experiments were also carried out in the absence of added cyclohexane, and the methyl vinyl ketone and methacrolein data were consistent with formation from both the OH radical and O3 reactions with isoprene. The data obtained are compared with the literature data and the reaction mechanism discussed.

  35. ATKINSON R (1991). "KINETICS AND MECHANISMS OF THE GAS-PHASE REACTIONS OF THE NO3 RADICAL WITH ORGANIC-COMPOUNDS." JOURNAL OF PHYSICAL AND CHEMICAL REFERENCE DATA 20(3): 459-507.
    ABSTRACT
    A substantial data base concerning the rate constants for the gas-phase reactions of the nitrate (NO3) radical with organic compounds is now available, with rate constants having been determined using both absolute and relative rate methods. To date, the majority of these kinetic data have been obtained at room temperature using relative rate techniques utilizing both the reactions of the NO3 radical with other organic compounds and the equilibrium constant for the NO3 + NO2 reversible N2O5 reactions as the reference reaction. In this article, the literature kinetic and mechanistic data for the gas-phase reactions of the NO3 radical with organic compounds (through late 1990) have been tabulated, reviewed and evaluated. While this available data base exhibits generally good agreement and self-consistency, further absolute rate data are needed, preferably as a function of temperature. Most importantly, mechanistic and product data for the reactions of the NO3 radical with organic compounds need to be obtained.

  36. WAYNE RP, BARNES I, et al. (1991). "THE NITRATE RADICAL - PHYSICS, CHEMISTRY, AND THE ATMOSPHERE." ATMOSPHERIC ENVIRONMENT PART A-GENERAL TOPICS 25(1): 203.
    ABSTRACT
    This review surveys the present state of knowledge of the nitrate (NO3) radical. Laboratory data on the physics and chemistry of the radical and atmospheric determinations of the concentrations of the radical are both considered. One aim of the review is to highlight the relationship between the laboratory and the atmospheric studies. Although the emphasis of the review is on gas-phase processes, relevant studies conducted in condensed phases are mentioned because of their potential importance in the interpretation of cloud and aerosol chemistry. The spectroscopy, structure, and photochemistry of the radical are examined. Here, the object is to establish the spectroscopic basis for detection of the radical and measurement of its concentration in the laboratory and in the atmosphere. Infrared, visible, and paramagnetic resonance spectra are considered. An important quality discussed is the absorption cross section in the visible region, which is required for quantitative measurements. Interpretation of the spectroscopic features requires an understanding of the geometrical and electronic structure of the radical in its ground and excited states; there is still some controversy about the groundstate geometry, but the most recent experimental evidence (eg from laser induced fluorescence) and theoretical calculations suggest that the radical has D3h symmetry. Photodissociation of the radical is important in the atmosphere, and the product channels, quantum yields, and dissociation dynamics are discussed. A short examination of the thermodynamics (heat and entropy of formation) of the radical is presented. The main exposition of laboratory studies of the chemistry of the nitrate radical is preceded by a consideration of the techniques used for kinetic and mechanistic studies. Method for the generation and detection of the radical and the kinetic tools employed are all presented. The exact nature of the technique used in individual studies has some relevance to the way in which data must be analysed, and to the type of mechanistic information that can be extracted. Continuous and stopped flow, flash photolysis and pulse radiolysis, molecular modulation, and static reactor techniques can all provide absolute kinetic data, while relative rate measurements have been a further rich source of information. The treatment of the chemical reactions of the nitrate radical is formally divided into the interactions with non-radical inorganic (deemed to include NO and NO2) and organic species, and with atoms and free radicals. In general, the reactions with open-shell species are much more rapid than those with closed-shell reactants. With the closed-shell partners, addition reactions are faster than abstraction reactions. An attempt is made to consider critically the published data on most reactions of importance, and to tabulate rate constants and temperature dependences where possible. However, it is not the objective of this review to provide recommendations for rate parameters. Evidence for the products of the reactions is sought, and for the branching ratios into the various channels where more than one exists. One theme of this part of the review is the elucidation of correlations of reactivity with structure and with the reactions of other radical species such as OH. The review turns next to a consideration of the role of NO3 in the atmosphere, of its atmospheric sources and sinks, and of field measurements of concentrations of the radical. Long-path visible-absorption spectroscopy and matrix-isolation ESR have both been used successfully in field measurements in the troposphere as well as the stratosphere. Balloon-borne instruments and ground-based remote sensing have been used to obtain stratospheric concentrations. Two of the most important implications of the measurements are that the stratospheric profiles are consistent with accepted chemistry (and, in particular, do not require the postulation of an unidentified scavenging mechanism that had, at one stage, been proposed), and that the highly variable night-time tropospheric concentrations imply that NO3 is a reactive tropospheric constituent. The inter-relation between laboratory studies and atmospheric observations, and the problems in extrapolating laboratory data to atmospheric conditions, are both explored. Initiation of night-time chemical transformations by NO3 and the possible production of OH are considered. The available information is then brought together to see how far NO3 is a sensitive indicator of the state of the atmosphere, and some speculations are presented about the involvement of NO3 (or N2O5) in damage to trees and plants.

  37. Papagni C, Arey J, et al. (2000). "Rate constants for the gas-phase reactions of a series of C-3-C-6 aldehydes with OH and NO3 radicals." INTERNATIONAL JOURNAL OF CHEMICAL KINETICS 32(2): 79-84.
    ABSTRACT
    By using relative rate methods, rate constants for the gas-phase reactions of OH and NO3 radicals with propanal, butanal, pentanal, and hexanal have been measured at 296 +/- 2 K and atmospheric pressure of air. By using methyl vinyl ketone as the reference compound, the rate constants obtained for the OH radical reactions (in units of 10(-12) cm(3) molecule(-1) s(-1)) were propanal, 20.2 +/- 1.4; butanal, 24.7 +/- 1.5; pentanal, 29.9 +/- 1.9; and hexanal, 31.7 +/- 1.5. By using methacrolein and 1-butene as the reference compounds, the rate constants obtained for the NO3 radical reactions (in units of 10(-15) cm(3) molecule(-1) s(-1)) were propanal, 7.1 +/- 0.4; butanal, 11.2 +/- 1.5; pentanal, 14.1 +/- 1.6; and hexanal, 14.9 +/- 1.3. The dominant tropospheric loss process for the aldehydes studied here is calculated to be by reaction with the OH radical, with calculated lifetimes of a few hours during daytime. (C) 2000 John Wiley & Sons, Inc.

  38. Ullerstam M, Ljungstrom E, et al. (2000). "Reactions of acrolein, crotonaldehyde and pivalaldehyde with Cl atoms: structure-activity relationship and comparison with OH and NO3 reactions." PHYSICAL CHEMISTRY CHEMICAL PHYSICS 3(6): 986-992.
    ABSTRACT
    Rate coefficients for the reaction of acrolein (prop-2-en-1-al), crotonaldehyde (but-2-en-1-al) and pivalaldehyde (2,2-dimethylpropanal) with chlorine atoms were determined. The resulting rate coefficients were (1.8 +/-0.3)x10(-10), (2.2 +/- 0.4)x10(-10) and (1.2 +/-0.2)x10(-10) (c molecule(-1) s(-1)) for acrolein, crotonaldehyde and pivalaldehyde, respectively. Rate coefficients for chlorine atom reaction with propanal, butanal, 2-methylpropanal and trans-but-2-ene were determined to be (1.2 +/-0.2)x10(-10), (1.5 +/-0.3)x10(-10), (1.5 +/- 0.3)x10(-10) and (3.0 +/-0.6)x10(-10) (c molecule(-1) s(-1)), respectively. The relative rate technique was used with propene as the reference compound. The experiments were carried out at 297 +/-2 K and 1020 +/-2 mbar using a 0.153 borosilicate glass reactor with long-path FTIR spectroscopy as the analytical tool. Synthetic air and nitrogen were used as bath gases. Literature values of the corresponding hydroxyl and nitrate radical rate coefficients were confirmed. The chemical characteristics of the organic substances have a limited influence on the reactivity with Cl, a larger effect in the OH-case but are decisive for the NO3 reactions. Introduction of an aldehydic carbonyl group into an unsaturated compound reduces the reactivity of a neighboring double bond for reaction with all three radicals. The unsaturated aldehydes reacting with NO3 show a rate coefficient that is lower than both the corresponding simple alkene and aliphatic aldehyde, indicating that also the reactivity of the aldehydic hydrogen atom is affected. The results show that during the morning hours, Cl atoms may be the most significant oxidising agent for organic substances in urban coastal air.

  39. D'Anna B, Andresen W, et al. (2001). "Kinetic study of OH and NO3 radical reactions with 14 aliphatic aldehydes." PHYSICAL CHEMISTRY CHEMICAL PHYSICS 3(15): 3057-3063.
    ABSTRACT
    Rate coefficients for the reactions of NO3 and OH radicals with 14 aliphatic C2 to C6 aldehydes in purified air at 298 +/-2 K and 1.00 +/-0.01 atm have been determined by the relative rate method using a static reactor equipped with long-path FTIR detection. The aldehydes studied comprise: C2-acetaldehyde; C3-propanal; C4-butanal and 2-methylpropanal; C5-pentanal, 2-methylbutanal, 3-methylbutanal and 2,2-dimethyl-propanal; C6-hexanal, 2-methyl-pentanal, 3-methylpentanal, 4-methylpentanal, 3,3-dimethylbutanal, and 2-ethylbutanal. The new data establish that the gas-phase reactivity of aliphatic aldehydes towards the NO3 and OH radicals follow the linear free energy relationship typical of addition reactions although the net result of the reactions is a H-abstraction. The experiments also indicate that more than 95% of the room temperature NO3 reaction with aliphatic aldehydes proceeds through an abstraction of the aldehydic hydrogen. The structure activity relationship for estimation of rate coefficients of the NO3 radical reaction with saturated organics (J. Phys. Chem. Ref. Data, 1991, 20, 45) fails completely for aliphatic aldehydes.

  40. LANGER S and LJUNGSTROM E (1994). "RATES OF REACTION BETWEEN THE NITRATE RADICAL AND SOME ALIPHATIC ETHERS." INTERNATIONAL JOURNAL OF CHEMICAL KINETICS 26(3): 367-380.
    ABSTRACT
    Rate coefficients for the reaction of NO3 with dimethyl ether, diethyl ether, di-n-propyl ether, and methyl t-butyl ether (MTBE) have been determined. Absolute rates were measured at temperatures between 258 and 373 K using the fast flow-discharge technique. Relative rate experiments were also made at 295 K in a reactor equipped with White optics and using FTIR spectroscopy to follow the reactions. The measured rate coefficients (in units of 10(-15) cm3 molecule-1 s-1) at 295 K are: 0.26 +/- 0.11, 2.80 +/- 0.23, 6.49 +/- 0.65, and 0.64 +/- 0.06 for dimethyl ether, diethyl ether, di-n-propyl ether, and methyl t-butyl ether, respectively. The corresponding activation energies are 21.0 +/- 5.0, 17.2 +/- 4.0, 15.5 +/- 2.1, and 20.1 +/- 1.7 kJ mole-1. The error limits correspond to the 95%-confidence interval. (C) 1994 John Wiley & Sons, Inc.

  41. SKOV H, HJORTH J, et al. (1992). "PRODUCTS AND MECHANISMS OF THE REACTIONS OF THE NITRATE RADICAL (NO3) WITH ISOPRENE, 1,3-BUTADIENE AND 2,3-DIMETHYL-1,3-BUTADIENE IN AIR." ATMOSPHERIC ENVIRONMENT PART A-GENERAL TOPICS 26(15): 2771-2783.
    ABSTRACT
    Products and mechanisms of the reaction of NO3 with isoprene have been studied under simulated atmospheric conditions with in situ FTIR spectroscopy as analytical technique. The study addressed also the reactions of NO3 with 1,3-butadiene and 2,3-dimethyl-1,3-butadiene as well as with the deuterated species 1,1,4,4-d4-1,3-butadiene, d6-1,3-butadiene and 4,4-d2-2-methyl-1,3-butadiene (d2-isoprene). The dienes examined apparently follow very similar reaction pathways. The decay of the intermediate peroxynitrates formed after the addition of NO3 to one of the methylene groups, leads to unsaturated ketone-nitrate, aldehyde-nitrate, alcohol-nitrate and perhaps also dinitrate species. The yield of unsubstituted carbonyl compounds was insignificant in the reactions of NO3 with 1,3-butadiene and isoprene. In the case of isoprene, NO3 reacts adding preferentially to the 1-position and 3-methyl-4-nitroxy-2-butenal appears to be the main product. 1,3-Butadiene predominantly reacts with NO3 via trans-1,4-addition and 1,2-addition while the cis-1,4-addition path is of minor importance. trans-4-Nitroxy-2-butenal and 1-nitroxy-3-buten-2-one were found as main products. Contrary to the daytime OH-initiated degradation of isoprene, the nighttime oxidation of isoprene by NO3 leads to formation of large quantities of organic nitrate compounds; this may have consequences for the tropospheric NO(y) budget as briefly discussed.

  42. Jenkin ME, Saunders SM, et al. (1997). "The tropospheric degradation of volatile organic compounds: A protocol for mechanism development." ATMOSPHERIC ENVIRONMENT<31(1): 81-104.

    ABSTRACT
    Kinetic and mechanistic data relevant to the tropospheric oxidation of volatile organic compounds (VOCs) are used to define a series of rules for the construction of detailed degradation schemes for use in numerical models. These rules are intended to apply to the treatment of a wide range of non-aromatic hydrocarbons and oxygenated and chlorinated VOCs, and are currently being used to provide an up-to-date mechanism describing the degradation of a range of VOCs,and the production of secondary oxidants, for use in a model of the boundary layer over Europe. The schemes constructed using this protocol are applicable, however, to a wide range of ambient conditions, and may be employed in models of urban, rural or remote tropospheric environments, or for the simulation of secondary pollutant formation for a range of NOx or VOC emission scenarios. These schemes are believed to be particularly appropriate for comparative assessments of the formation of oxidants, such as ozone, from the degradation of organic compounds. The protocol is divided into a series of subsections dealing with initiation reactions, the reactions of the radical intermediates and the further degradation of first and subsequent generation products. The present work draws heavily on previous reviews and evaluations of data relevant to tropospheric chemistry. Where necessary, however, existing recommendations are adapted, or new rules are defined, to reflect recent improvements in the database, particularly with regard to the treatment of peroxy radical(RO(2)) reactions for which there have been major advances, even since comparatively recent reviews. The present protocol aims to take into consideration work available in the open literature up to the end of 1994, and some further studies known by the authors, which were under review at that time. A major disadvantage of explicit chemical mechanisms is the very large number of reactions potentially generated, if a series of rules is rigorously applied. The protocol aims to limit the number of reactions in a degradation scheme by applying a degree of strategic simplification, whilst maintaining the essential features of the chemistry. These simplification measures are described, and their influence is demonstrated and discussed. The resultant mechanisms are believed to provide a suitable starring point for the generation of reduced chemical mechanisms. Copyright (C) AEA Technology. Published by Elsevier Science Ltd

  43. Calvert JG and Pitts JN (1966). "Photochemistry." Wiley, New York.
  44. JENKIN ME and HAYMAN GD (1995). "KINETICS OF REACTIONS OF PRIMARY, SECONDARY AND TERTIARY BETA-HYDROXY PEROXYL RADICALS - APPLICATION TO ISOPRENE DEGRADATION." JOURNAL OF THE CHEMICAL SOCIETY-FARADAY TRANSACTIONS 91(13): 1911-1922.
    ABSTRACT
    The UV absorption spectra and kinetics of reactions of the primary, secondary and tertiary beta-hydroxy peroxyl radicals HOCH2CH2O2 CH3CH(OH)CH(O-2)CH3 and (CH3)(2)C(OH)C(O-2)(CH3)(2) at or near 298 K have been studied using both the molecular modulation (MM) and the laser flash photolysis (LFP) techniques. The radicals were produced by the UV photolysis (254 or 248 nm) of mixtures containing H2O2 and one of the symmetric monoalkenes ethene, (E)-but-2-ene and 2,3-dimethylbut-2-ene, diluted in air. The spectra of CH3CH(OH)CH(O-2)CH3 and (CH3)(2)C(OH)C(O-2)(CH3)(2) were found to be very similar to that measured previously for HOCH2CH2O2, with maximum cross-sections of ca. 4 x 10(-18) cm(2) molecule(-1) at 245 nm. At high monoalkene concentrations, the observed second-order removal of the peroxyl radicals (RO(2)) provided values of k(3obs) (in units of 10(-12) cm(3) molecule(-1) s(-1)) of 3.1 +/- 0.4, 0.84 +/- 0.06 and 0.0114 +/- 0.0017 for HOCH2CH2O2, CH3CH(OH)CH(O-2)CH3 and (CH3)(2)C(OH)C(O-2)(CH3)(2), respectively, the quoted values being the mean of the MM and LFP determinations: RO(2) + RO(2) --> products The values of k(3obs) are greater than the values for the elementary rate coefficients, k(3), owing to secondary removal of the RO(2) radicals. The details of the secondary chemistry and the probable magnitude of the additional removal are discussed. At low monoalkene concentrations, simultaneous production of HO2 in the systems allowed the reactions of RO(2) with HO2 to be investigated: RO(2) + HO2 --> ROOH + O-2 Values of k(2) (in units of 10(-11) cm(3) molecule(-1) s(-1)) of 1.5 +/- 0.3, 1.5 +/- 0.4 and ca. 2 were determined for HOCH2CH2O2, CH3CH(OH)CH(O-2)CH3 and (CH3)(2)C(OH)C(O-2)(CH3)(2), respectively, using the LFP technique. The kinetic data obtained in the present work, and those obtained previously for the allyl peroxyl radical, are used to infer rate coefficients for some of the reactions of the complex peroxyl radicals formed from the OH-initiated oxidation of isoprene. A mechanism describing the degradation of isoprene to first generation products is constructed using the derived coefficients, and key parameters obtained or inferred from other sources, which gives a reasonable description of product yields measured in the laboratory in both the presence and absence of NOx.

  45. Noziere B, Barnes I, et al. (1999). "Product study and mechanisms of the reactions of alpha-pinene and of pinonaldehyde with OH radicals." JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES 104(D19): 23645-23656.
    ABSTRACT
    The reactions of alpha-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 alpha-pinene experiments in the presence of NOx, pinonaldehyde, (87 +/- 20)%; total nitrates (18 +/- 9)%; formaldehyde, (23 +/- 9)%; acetone (9 +/- 6)%; for the alpha-pinene experiments in the absence of NO,: pinonaldehyde, (37 +/- 7)%; formaldehyde, (8 +/- 1)%; acetone, (7 +/- 2)%; for the pinonaldehyde experiments in the presence of NOx 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 alpha-pinene concentrations lower than 10(13) 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 alpha-pinene with OH in the presence of NOx has been proposed, including quantitative values for all the involved branching ratios.

  46. HAYMAN GD (1997). "Effects of Pollution Control on UV Exposure." AEA Technology Final Report (Ref: AEA/RCEC/22522001/R/002 Issue 1) AEA Technology, Oxfordshire.
  47. Vereecken L and Peeters J (2000). "Theoretical study of the formation of acetone in the OH-initiated atmospheric oxidation of alpha-pinene." JOURNAL OF PHYSICAL CHEMISTRY A 104(47): 11140-11146.
    ABSTRACT
    A mechanism is proposed for the formation of acetone in the OH-initiated atmospheric oxidation of alpha -pinene. In a first step, addition of the OH radical onto the alpha -pinene double bond forms a chemically activated tertiary radical P1OH(dagger). This activated radical can then for a certain fraction break its four-membered ring, leading to a 6-hydroxymenthen-8-yl radical, which is subsequently converted to a 6-hydroxymenthen-8-oxy radical by reaction with O-2 and NO, and elimination of an NO2 molecule. Finally, the 6-hydroxymenthen-8-oxy radical forms acetone by beta C-C bond rupture. For each of these steps, competing reactions are considered, as well as the site and stereospecificity of the reaction itself. To quantify the acetone yield, quantum chemical calculations were combined with RRKM-Master Equation analyses for most of the reactions; other branching ratios were estimated from available literature data. The total yield of acetone was obtained by propagating the relevant product fractions of each step in the mechanism. We find an acetone yield of 8.5%, in good agreement with available experimental data. The uncertainty interval is estimated at 4-16%. It should be emphasized that only the nascent, chemically activated P1OH(dagger); radicals contribute to the crucial ring-breaking isomerization step.

  48. Aschmann SM, Reissell A, et al. (1998). "Products of the gas phase reactions of the OH radical with alpha- and beta-pinene in the presence of NO." JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES 103(D19): 25553-25561.
    ABSTRACT
    Products of the gas phase reactions of the OH radical with alpha- and beta-pinene in the presence of NO have been investigated using gas chromatography and in situ atmospheric pressure ionization mass spectrometry (API-MS). Acetone was identified and quantified by gas chromatography with flame ionization detection and combined gas chromatography-mass spectrometry, with formation yields of 0.110 +/- 0.027 from the ct pinene reaction and 0.085 +/- 0.018 from the beta-pinene reaction. Acetone is a first-generation product and may arise after initial H atom abstraction from the tertiary allylic C-H bond at the 1 position and/or after OH radical addition at the 2 and 3 positions. Using API-MS and API-MS/MS analyses, in addition to the formation of pinonaldehyde from alpha-pinene and nopinone from beta-pinene, we have observed the formation of hydroxynitrates, dihydroxynitrates and dihydroxycarbonyl products of molecular weights 215, 231 and 184, respectively, from both alpha- and beta-pinene. Reaction schemes leading to the formation of these multifunctional product species, consistent with our understanding of the atmospheric chemistry of organic peroxy and alkoxy radicals, are presented.

  49. Orlando JJ, Noziere B, et al. (2000). "Product studies of the OH- and ozone-initiated oxidation of some monoterpenes." JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES 105(D9): 11561-11572.
    ABSTRACT
    The OH- and O-3-initiated oxidation of five monoterpenes (myrcene, terpinolene, Delta(3)-carene, alpha-pinene, and beta-pinene) has been studied in environmental chambers equipped with either a Fourier transform infrared spectrometer or a gas chromatography/flame ionization detector system. The OH-oxidation of myrcene and terpinolene is shown to lead to substantial yields of acetone (36 and 39%, respectively), while the acetone yield from the pinene compounds is quite small (4% and similar to 2%, for alpha- and beta-pinene, respectively). Formaldehyde has been identified as a major product (yields of 20-40%) in the OH-initiated oxidation of all five species. Formic acid was also observed in the OH-initiated oxidation of all five monoterpenes, with yields of 2% from beta-pinene and 5-9% from the other species studied. The production of acetone from the reaction of monoterpenes with ozone in the presence of an OH scavenger was measured. The yields of acetone for the O-3 reactions were alpha-pinene, 0.03 +/- 0.01; beta-pinene, 0.009 + 0.009; Delta(3)-carene, 0.10 +/- 0.015; myrcene, 0.25 +/- 0.06; and terpinolene, 0.50 + 0.06. The mechanism leading to the production of these compounds is discussed, as is the atmospheric relevance of the results. In particular, an estimate of the contribution of monoterpene oxidation to observed atmospheric levels of acetone and formic acid is made.

  50. BIGGS P, CANOSAMAS CE, et al. (1994). "INVESTIGATION INTO THE KINETICS AND MECHANISM OF THE REACTION OF NO3 WITH CH3O2 AT 298-K AND 2.5-TORR - A POTENTIAL SOURCE OF OH IN THE NIGHTTIME TROPOSPHERE." JOURNAL OF THE CHEMICAL SOCIETY-FARADAY TRANSACTIONS 90(9): 1205-1210.
    ABSTRACT
    The kinetics of the reaction CH3O2 + NO3 --> CH3O + NO2 + O2 (1) have been studied at 298 K and at pressures between 2 and 3 Torr of helium using the discharge-flow technique combined with laser-induced fluorescence detection of the methoxyl radical and measurements of the NO3 radical using visible absorption. Numerical modelling of the concentration-time profile of CH3O with or without NO3 and NO as a titrant has allowed us to show that CH3O is a product of reaction (1) and to derive a rate constant k1 = (1.0 +/- 0.6) x 10(-12) cm3 molecule-1 s-1, at 95% confidence limits. A comparison of the reactivities of NO3 and NO2 towards the species R, RO and RO2, where R = H or CH3, is given. The implication of reaction (1) in the possible production of OH in the atmosphere at night is discussed.

  51. BIGGS P, CANOSAMAS CE, et al. (1995). "RATE CONSTANTS FOR THE REACTIONS OF C2H5, C2H5O AND C2H5O2 RADICALS WITH NO3 AT 298 K AND 2.2 TORR." JOURNAL OF THE CHEMICAL SOCIETY-FARADAY TRANSACTIONS 91(5): 817-825.
    ABSTRACT
    A discharge-flow system equipped with a laser-induced fluorescence cell to detect the ethoxyl radical and an optical absorption cell to detect the nitrate radical has been used to measure the rate constants for the reactions C2H5 + NO3 --> products (1) C2H5O + NO3 --> products (2) C2H5O2 + NO3 --> products (3) at T = 298 K and P = 2.2 Torr. The major products of these reactions are C2H5O and NO2 for reaction (1), C2H5O2 and NO2 for reaction (2) and C2H5O, O-2 and NO2 for reaction (3). Reactions (2) and (3) are therefore highly coupled and, in order to determine the rate constants k(2) and k(3) for these reactions, two types of experiment were performed. In the first set of experiments, C2H5O was generated in situ via reaction (1) and allowed to react with NO3 and, in the second set of experiments, C2H5O2 was generated separately and allowed to react with NO3. A numerical model was then used to derive the following rate constants: k(1) = (4.0 +/- 1.0) x 10(-11) cm(3) molecule(-1) s(-1), k(2) = (3.5 +/- 1.0) x 10(-12) cm(3) molecule(-1) s(-1) and k(3) = (2.5 +/- 1.5) x 10(-12) cm(3) molecule(-1) s(-1). The errors quoted are not statistically derived, but rather represent ranges over which the numerical simulations fit the experimental data adequately. The mechanisms for reactions (1) and (2) are discussed in terms of the QRRK treatment and the atmospheric implications of reaction (3) are considered.

  52. DAELE V, LAVERDET G, et al. (1995). "KINETICS OF THE REACTIONS CH3O+NO, CH3O+NO3, AND CH3O2+NO3." JOURNAL OF PHYSICAL CHEMISTRY 99(5): 1470-1477.
    ABSTRACT
    A discharge flow reactor coupled to laser-induced fluorescence (LIF) and mass spectrometry has been used to study the kinetics of the reactions of CH3O with NO and NO3. The value of the rate constant for the reaction CH3O + NO --> products at 298 K and at 1 Torr of He has been found to be k = (4.8 +/- 0.4) x 10(-12) cm(3) molecule(-1) s(-1), in good agreement with the literature data. From the kinetic analysis of CH3O by LIF, the reaction CH3O +/- NO3 --> CH3O2 + NO2 (1) has been found to be followed by the reaction CH3O2 + NO3 --> CH3O + NO2 + O-2 (2). Modeling calculations gave for the rate constants of these two reactions, at 298 K, k(1) = (1.8 +/- 0.5) x 10(-12) cm(3) molecule(-1) s(-1) and k(2) = (1.2 +/- 0.6) x 10(-12) cm(3) molecule(-1) s(-1). Comparison with recent Literature data is given, and the atmospheric implication for nighttime chemistry is briefly discussed.

  53. Helleis F, Moortgat GK, et al. (1996). "Kinetic investigations of the reactions of CD3O2 with NO and NO3 at 298 K." JOURNAL OF PHYSICAL CHEMISTRY 100(45): 17846-17854.
    ABSTRACT
    The reactions of methylperoxy radicals with NO3 and NO were investigated at room temperature using the method of discharge flow/mass spectrometry, For reaction with NO, data were obtained for normal and deuterated methylperoxy. k(CH3O2 + NO) = (7.5 +/- 1.0) x 10(-12) cm(3) molecule(-1) s(-1) and k(CD3O2 + NO) = (8.6 +/- 1.0) x 10(-12) cm(3) molecule(-1) s(-1). The rate constant for reaction of CD3O2 with NO3 was found to be k(CD3O2 + NO3 --> CD3O + NO2 + O-2) = (1.3 +/- 0.2) x 10(-12) cm(3) molecule(-1) s(-1). In addition, rate constants were obtained for the reaction of CD3O with NO3: k(CD3O + NO3 --> CD3O2 + NO2) = (3.7 +/- 0.8) x 10(-12) cm(3) molecule(-1) s(-1), k(CD3O + NO3 --> DCDO + DNO3) = (5.6 +/- 1.0) x 10(-13) cm(3) molecule(-1) s(-1).

  54. Ray A, Daele V, et al. (1996). "Kinetic study of the reactions of C2H5O and C2H5O2 with NO3 at 298 K." JOURNAL OF PHYSICAL CHEMISTRY 100(14): 5737-5744.
    ABSTRACT
    A discharge flow reactor coupled to laser-induced fluorescence and mass spectrometry, for the detection of ethoxy and nitrate radicals, respectively, has been used to study the kinetics of the reactions of C2H5O and C2H5O2 with NO3 at ca. 1 Torr of helium and 298 K. From the analysis of the C2H5O concentration-time profiles in two sets of experiments, the reactions C2H5O + NO3 --> C2H5O2 + NO2 (1) and C2H5O2 + NO3 --> C2H5O + NO2 + O-2 (2) were observed to be strongly coupled. The rate constants were derived from modeling calculations, k(1) = (3.3 +/- 0.9) x 10(-12) cm(3) molecule(-1) s(-1) and k(2) = (2.3 +/- 0.5) x 10(-12) cm(3) molecule(-1) s(-1). These data are compared with other very recent literature data, and their atmospheric significance for nighttime chemistry is briefly discussed.

  55. CanosaMas CE, King MD, et al. (1996). "Is the reaction between CH3C(O)O-2 and NO3 important in the night-time troposphere?" JOURNAL OF THE CHEMICAL SOCIETY-FARADAY TRANSACTIONS 92(12): 2211-2222.
    ABSTRACT
    A discharge-flow system equipped with a laser-induced fluorescence (LIF) cell to detect NO2 and a multi-pass absorption cell to detect NO3 has been used to study the reaction CH3C(O)O-2+NO3-->CH3C(O)O+NO2+O-2 (1) at T = 403-443 K and P = 2-2.4 Torr. The rate constant was found to be independent of temperature with a value of k(1) = (4+/-1) x 10(-12) cm(3) molecule(-1) s(-1). The likely mechanism for the reaction is discussed. The atmospheric implications of reaction (1) are investigated using a range of models and several case studies are presented, comparing model results with actual held measurements. It is concluded that reaction (1) participates in a cycle which can generate OH at night. This reaction cycle (see text) can operate throughout the continental boundary layer, but may even occur in remote regions.

  56. ROWLEY DM, LESCLAUX R, et al. (1992). "KINETIC AND MECHANISTIC STUDIES OF THE REACTIONS OF CYCLOPENTYLPEROXY AND CYCLOHEXYLPEROXY RADICALS WITH HO2." JOURNAL OF PHYSICAL CHEMISTRY 96(12): 4889-4894.
    ABSTRACT
    The kinetics and mechanism of the reactions c-C5H9O2 + HO2 --> c-C5H9OOH + O2 (1) and c-C6H11O2 + HO2 --> c-C6H11OOH + O2 (2 have been studied using both the flash photolysis/UV absorption and continuous photolysis/FTIR product analysis techniques. End product analysis experiments at 295 +/- 2 K demonstrated that the yield of hydroperoxide was (96 +/- 3) % and (99 +/- 3)% for reactions 1 and 2, respectively, although systematic errors could add an additional 15% uncertainty. Experiments between 248 and 364 K showed that k1 and k2 demonstrated virtually indistinguishable kinetic behavior at all temperatures, with k1/cm3 molecule-1 s-1 = (2.1 +/- 1.3) x 10(-13) exp((1323 +/-185) K/T) and k2/cm3 molecule-1 s-1 = (2.6 +/- 1.2) x 10(-13) exp((1245 +/- 124) K/T). Absolute uncertainties on kl and k2, including experimental scatter and uncertainties in the analysis parameters, are estimated to be 18%. No dependence of k1 or k2 on pressure between 200 and 760 Torr was found. The room temperature rate constants for reactions 1 and 2 are significantly greater than those measured for other alkylperoxy radicals to date. The reactions of Cl atoms with cyclopentane, Cl + c-C5H 10 --> HCl + c-C5H9 (6) and cyclohexane, Cl + c-C6H12 --> HCl + c-C6H11 (8) were measured relative to that with methanol, Cl + CH3OH --> HCl + CH2OH (4). Neither k6 nor k8 varied significantly with temperature over the range 248-364 K, with k6/cm3 molecule-1 s-1 = (2.3 +/- 0.2) x 10(-10) and k8/cm3 molecule-1 s-1 = (2.4 +/- 0.3) x 10(-10), using k4/cm3 molecules-1 s-1 = 5.7 x 10(-11). Errors are 1-sigma and represent experimental scatter only, unless stated otherwise.

  57. Boyd AA, Lesclaux R, et al. (1996). "A spectroscopic, kinetic, and product study of the (CH3)(2)C(OH)CH2O2 radical self-reaction and reaction with HO2." JOURNAL OF PHYSICAL CHEMISTRY 100(16): 6594-6603.
    ABSTRACT
    A flash photolysis technique was used to measure the UV absorption spectrum of the peroxy radical (CH3)(2)C(OH)CH2O2 formed in the (CH3)(3)COH/Cl/O-2 reaction system and to study the kinetics of its self reaction and reaction with the HO2 radical at room temperature and above: 2(CH3)(2)C(OH)CH2O2 --> 2(CH3)(2)C(OH)CH2O + O-2 (5a); 2(CH3)(2)C(OH)CH2O2 --> (CH3)(2)C(OH)CH2OH + (CH3)(2)C(OH)CHO + O-2 (5b); (CH3)(2)C(OH)CH2O2 + HO2 --> (CH3)(2)C(OH)CH2OOH + O-2 (8). The spectrum of the radical resembles that of other beta-hydroxyl substituted peroxy radicals in form and magnitude. Use of this and other known absorption cross sections in an appropriate chemical model of the system allowed k(5), the branching ratio alpha (=k(5a)/k(5)), and k(8) to be derived as a function of temperature (T = 306-398 K) by an iterative procedure involving the simulation of experimental decay traces recorded at several wavelengths: k(5) = (1.4 +/- 0.6) x 10(-14) exp[(1740 +/- 150)K/T) cm(3) molecule(-1) s(-1); alpha = 0.59 +/- 0.15 (no discernible temperature dependence over this range); k(8) = (5.6 +/- 2.0) x 10(-14) exp[(1650 +/- 130)K/T) cm(3) molecule(-1) s(-1). These expressions yield values for k(5) and k(8) of 4.8 and 14 x 10(-12) cm(3) molecule(-1) s(-1) at 298 K, confirming the phenomena both of enhanced self reaction reactivity upon beta-OH substitution and of a large rate coefficient for the reaction of all greater than or equal to C-2 peroxy radicals with HO2. Product studies of reaction 5, using an FTIR-smog chamber system, confirmed the assumed reaction mechanism in 700 Torr of air at 296 K, namely the unique formation of the peroxy radical of interest, rapid decomposition of the alkoxy radical (formed in reaction 5a) through C-C bond scission, and subsequent reaction with O-2 to yield formaldehyde and acetone (and HO2). A similar fate for the (CH3)(2)C(OH)CH2O radical is expected as part of the degradation of tert-butyl alcohol (TBA) and isobutene under tropospheric conditions. Furthermore, the product distribution results, when combined with the extrapolated k(5) and k(8) values, allow alpha be determined as 0.60 +/- 0.07 at 296 K, consistent with the value obtained from the flash photolysis study. As part of the smog chamber work, a relative rate technique was used to measure the rate coefficient for the reaction of Cl atoms with (CH3)(2)C(CH2Cl)OH as (9.2 +/- 1.1) x 10(-12) cm(3) molecule(-1) s(-1) at 296 K.

  58. Lesclaux R, Boyd AA, et al. (1998). "Reactions of peroxy and alkoxy radicals relevant to biogenic hydrocarbon oxidation." Contribution to "Structure activity relationships for the oxidation of biogenic volatile organic compounds (SARBVOC) - Final Report" REF: ENV-CT95-0031.
  59. BURROWS JP, MOORTGAT GK, et al. (1989). "INETICS AND MECHANISM OF THE PHOTOOXIDATION OF FORMALDEHYDE 2. MOLECULAR MODULATION STUDIES." JOURNAL OF PHYSICAL CHEMISTRY 93(6): 2375-2382.
  60. WALLINGTON TJ, HURLEY MD, et al. (1993). "FTIR PRODUCT STUDY OF THE REACTION OF CH3OCH2O2+HO2." CHEMICAL PHYSICS LETTERS 211(1): 41-47.
    ABSTRACT
    Fourier transform infrared spectroscopy was used to identify CH3OCHO and CH3OCH2OOH as products of the gas-phase reaction of CH3OCH2O2 radicals with HO2 radicals. At 700 Torr and 295 +/- 2K, branching ratios of k1a/k1 = 0.53 +/- 0.08 and k1b/k1 = 0.40 +/- 0.04 were established. Quoted errors are 2 standard deviations together with our estimate of systematic uncertainties. (CH3OCH2O2+HO2-->CH3OCH2OOH+O2 (1a), CH3OCH2O2+HO2-->CH3OCHO+O2+ H2O (1b).) This result is discussed with respect to previous literature data and to computer models of atmospheric chemistry. As part of this work, the rate constants for the reaction of Cl atoms with CH3OCH2OOH and CH3OCHO were determined to be (6.1 +/- 0.3) x 10(-11) and (1.4 +/- 0.1) x 10(-12) cm3 molecule-1 s-1, respectively.

  61. Lesclaux R (1997). "Combination of peroxyl radicals in the gas phase." in "Peroxyl Radicals" (Ed) Alfassi ZB John Wiley and Sons.
  62. MADRONICH S and CALVERT JG (1990). "PERMUTATION REACTIONS OF ORGANIC PEROXY-RADICALS IN THE TROPOSPHERE." JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES 95(D5): 5697-5715.
  63. Jenkin ME, Boyd AA, et al. (1998). "Peroxy radical kinetics resulting from the OH-Initiated oxidation of 1,3-butadiene, 2,3-dimethyl-1,3-butadiene and isoprene." JOURNAL OF ATMOSPHERIC CHEMISTRY 29(3): 267-298.
    ABSTRACT
    The laser flash photolysis/UV absorption spectrometry technique has been used to investigate the kinetics of the peroxy radical permutation reactions (i.e. self and cross reactions) arising from the OH-initiated oxidation of isoprene (2-methyl-1,3-butadiene), and of the simpler, but related conjugated dienes, 1,3-butadiene and 2,3-dimethyl-1,3-butadiene, The results of the two simpler systems are analysed to provide values of the rate coefficients for the 6 peroxy radical permutation reactions of the three types of isomeric peroxy radical produced in each system (T = 298 K, P = 760 Torr). The rate coefficients are all significantly larger than values estimated previously by extrapolation of structure-reactivity relationships based on the kinetics of a limited dataset of simpler radicals containing similar structural features. The results are discussed in terms of trends in self and cross reaction reactivity of primary, secondary and tertiary peroxy radicals containing combinations of allyl, beta-hydroxy and delta-hydroxy functionalities. Since the peroxy radicals formed in these systems are structurally very similar to those formed in the isoprene system, the kinetic parameters derived from the results of the simpler systems are used to assist the assignment of kinetic parameters to the 21 permutation reactions of the six types of isomeric peroxy radical generated in the isoprene system. Kinetic models describing the OH-initiated degradation of all three conjugated dienes to first generation products in the absence of NOx are recommended, which are also consistent with available end product studies. The model for isoprene is considered to be a further improvement on that suggested previously for its OH-initiated oxidation in the absence of NOx. The mechanism is further extended to include chemistry applicable to 'NOx-present' conditions, and calculated product yields are compared with those reported in the literature.

  64. BARNES I, BECKER KH, et al. (1992). "FTIR PRODUCT STUDY OF THE SELF-REACTION OF BETA-HYDROXYETHYL PEROXY-RADICALS." CHEMICAL PHYSICS LETTERS 203(2-3): 295-301.
    ABSTRACT
    Using long-path FTIR absorption spectroscopy, the products of the self-reaction of beta-hydroxyethyl peroxy radicals (HOCH2CH2O2) produced by the 254 nm photolysis of 2-iodoethanol and ethene/H2O2 have been investigated at 295 +/- 3 K for various total pressures (N2 + O2) and different 02 Partial pressures. From the observed products, glycolaldehyde, ethanediol and formaldehyde, a branching ratio alpha = k9a/(k9a + k9b) = 0.5 +/- 0.1 has been obtained for the radical-producing channel of the self-reaction. Beta-hydroxyethyl hydroperoxide (HOCH2CH2OOH) was also observed as a product and the first IR spectrum of this compound is reported. Preliminary studies on the products of the reaction of OH with 1,2-ethanediol, which results mainly in the formation of glycolaldehyde, are also presented.

  65. JENKIN ME, MURRELLS TP, et al. (1993). "KINETICS AND PRODUCT STUDY OF THE SELF-REACTIONS OF ALLYL AND ALLYL PEROXY-RADICALS AT 296-K." JOURNAL OF THE CHEMICAL SOCIETY-FARADAY TRANSACTIONS 89(3): 433-446.
    ABSTRACT
    The laser flash photolysis technique, coupled with UV absorption spectroscopy, has been used to investigate the UV spectra and kinetics of reactions of the allyl radical (CH2-CHCH2) and the allyl peroxy radical (CH2-CHCH2O2) at 296 K and total pressures near atmospheric. CH2-CHCH2 radicals were generated by the 193 nm photolysis of hexa-1,5-diene-N2 mixtures, or the 248 nm photolysis of allyl iodide-N2 mixtures. The 193 nm photolysis of hexa-1,5-diene-02-N2 mixtures was used to generate CH2-CHCH2O2. The low resolution spectrum of CH2-CHCH2 Was characterised in the range 210-232.5 nm. The absolute absorption cross-section near the maximum, sigma (220 nm) = (5.8 +/- 0.8) x 10(-17) cm2 molecule-1, calibrated relative to the loss of allyl iodide, is in good agreement with the single published determination. The observed time dependence of CH2-CHCH2 in the various chemical systems allowed measurement of rate coefficients for the following reactions 2CH2=CHCH2 (+M) --> CH2=CHCH2CH2CH=CH2 (+M) (10) CH2=CHCH2 + I (+M) --> CH2=CHCH2I (+M) (12) CH2=CHCH2 + 02 (+M) --> CH2=CHCH2O2 (+M) (7) The parameters obtained were k10 = (3.0 +/- 0.5) x 10(-11), k12 = (1.6 +/- 0.6) x 10(-10), and k7 = (6 +/- 2) x 10(-13) cm3 molecule-1 s-1. The UV absorption spectrum of CH2=CHCH2O2, characterised in the wavelength range 210-300 nm, is typical of an organic peroxy radical, with a peak cross-section of (6.2 +/- 0.9) x 10(-18) CM2 molecule-1 at 235 nm. CH2=CHCH2O2 displayed second-order kinetic behaviour indicative of its removal via the self-reaction. 2CH2=CHCH2O2 --> 2CH2=CHCH2O + O2 (13a) --> CH2=CHCHO + CH2=CHCH2OH + O2 (13b) The observed rate coefficient, k13obs = (1-1 +/- 0.2) x 10(-12) cm3 molecule-1 s-1, is greater than the elementary coefficient, k13, owing to secondary removal of CH2=CHCH2O2. The observed and elementary coefficients are related by the expression k13obs = (1 + alpha13)k13, where alpha13 = k13a/k13. Associated long pathlength Fourier transform infrared (FTIR) measurements of the products of the 253.7 nm initiated photo-oxidation of allyl iodide, allowed the product channels of reaction (13) to be identified and quantified, and a value of alpha13 = 0.61 +/- 0.07 was determined, leading to k13 = (6.8 +/- 1.3) x 10(3) CM-13 Molecule-1 s-1. The kinetic and mechanistic data obtained for CH2=CHCH2O2, and those measured previously in this laboratory for HOCH2CH2O2, are used to infer average rate coefficients for peroxy radicals (RO2) formed in the OH-initiated oxidation of isoprene. A simple box model of the planetary boundary layer is used to demonstrate the potential impact of elevated concentrations of isoprene on ambient levels of OH, HO2, RO2, O3 and NO(x).

  66. JENKIN ME, HAYMAN GD, et al. (1993). "KINETIC AND MECHANISTIC STUDY OF THE SELF-REACTION OF CH3OCH2O2 RADICALS AT ROOM-TEMPERATURE." JOURNAL OF PHYSICAL CHEMISTRY 97(45): 11712-11723.
    ABSTRACT
    The UV absorption spectrum and kinetics of the self reaction of CH3OCH2O2 at 298 K have been studied using both the modulated photolysis of Cl2/CH3OCH3/O2/N2 mixtures and the pulse radiolysis of SF6/CH3OCH3/O2 mixtures. The spectrum, characterized in the range 200-290 nm, is in good agreement with the single published determination.8 The observed second-order removal kinetics of CH3OCH2O2, k5obs, were found to be sensitive to both the variation of total pressure (17-760 Torr) and the composition of the reaction mixtures: 2CH3OCH2O2 -->2CH3OCH2O + O2 (5a); --> CH3OCHO + CH3OCH2OH + O2 (5b). The kinetic studies and a detailed product investigation using long path length FTIR spectroscopy (T = 295 K; Cl2/CH3OCH3/O2/N2 system) provide evidence to support a mechanism involving the rapid thermal decomposition of CH3-OCH2O by H atom ejection occurring in competition with the reaction with O2: CH3OCH2O(+M)-->CH3OCHO + H (+M) (6); CH3OCH2O + O2 --> CH3OCHO + HO2 (4). The complications in the measured values of k5obs in the present studies, and those reported previously,8 are believed to occur as a direct result of formation of H atoms from reaction 6. Accordingly, a pressure-independent value of k5 = (2.1 +/- 0.3) X 10(-12) cm3 molecule-1 s-1 is derived for the elementary rate coefficient at 298 K, with identical values of the branching ratio alpha = k5a/k5 = 0.7 +/- 0.1 determined independently from the FTIR product studies and the modulated photolysis experiments. As part of this work, the rate coefficient for the reaction of Cl atoms with CH3OCH2Cl was found to be (2.9 +/- 0.2) x 10(-11) cm3 molecule(-1) s-1.

  67. BRIDIER I, VEYRET B, et al. (1993). "FLASH-PHOTOLYSIS STUDY OF THE UV SPECTRUM AND KINETICS OF REACTIONS OF THE ACETONYLPEROXY RADICAL." JOURNAL OF THE CHEMICAL SOCIETY-FARADAY TRANSACTIONS 89(16): 2993-2997.
    ABSTRACT
    The flash-photolysis-UV-absorption method was used to study the UV spectrum and the kinetics of the CH3C(O)CH2O2 radical formed in the presence of oxygen via the reaction between Cl atoms and acetone. Results were analysed in the light of the results of the preceding article describing work using end-product analysis. The peroxy radical CH3C(O)CH2O2 absorbs in the UV with two maxima at around 230 and 290 nm. This peroxy radical reacts according to: 2CH3C(O)CH2O2 --> 2CH3C(O)CH2O + O2 (7a) and --> CH3C(O)CH2OH + CH3C(O)CHO + O2 (7b) with k7 = (8.0 +/- 2.0) x 10(-12) CM3 molecule-1 s-1 and k7a/k7 = (0.75 +/- 0.1). The kinetics of the reactions between CH3C(O)CH2O2 and the CH3C(O)O2, CH3O2 and HO2 radicals were determined by adding acetaldehyde, methane or methanol to the photolysis mixtures: CH3C(O)CH2O2 + CH3C(O)O2 --> O2 + CH3C(O)CH2O + CH3 + CO2 (11a); --> O2 + CH3C(O)OH + CH3C(O)CHO (11b); k11 = (5.0 +/- 2.0) x 10(-12) CM3 Molecule-1 s-1; CH3C(O)CH2O2 + CH3O2 --> O2 + CH3C(O)CH2O + CH3O (14a); --> O2 + CH3C(O)CHO + CH3OH (14b); --> O2 + CH3C(O)CH2OH + HCHO (14c); k14 = (3.8 +/- 0.4) x 10(-12) CM3 molecule-1 s-1 and k14a/k14 = 0.3 +/- 0.1 while k14b and k14c could not be distinguished; CH3C(O)CH2O2 + HO2 --> CH3C(O)CH2O2H + O2 (16), k16 = (9.0 +/- 1.0) x 10(-12) cm3 molecule-1 s-1. All experiments were performed at 298 K and 760 Torr.

  68. CATOIRE V, LESCLAUX R, et al. (1994). "KINETIC-STUDY OF THE REACTIONS OF CH2CLO2 WITH ITSELF AND WITH HO2, AND THEORETICAL-STUDY OF THE REACTIONS OF CH2CLO, BETWEEN 251-K AND 600-K." JOURNAL OF PHYSICAL CHEMISTRY 98(11): 2889-2898.
    ABSTRACT
    The UV absorption spectrum, self-reaction (2CH2ClO2 --> 2CH2ClO + O2 (1)) kinetics and the kinetics of the reaction with HO2 (CH2ClO2 + HO2 --> products (3)) of the chloromethylperoxy radical, CH2ClO2, have been studied between 251 and 600 K and at 760 Torr total pressure. Chloromethylperoxy radicals were produced by the flash photolysis of Cl2/CH3Cl/O2/N2 mixtures; for the study of reaction 3, chloromethylperoxy and hydroperoxy radicals were produced simultaneously by the flash photolysis of Cl2/CH3Cl/CH3OH/O2/N2 mixtures. Radical concentrations were monitored by UV absorption spectrometry from 205 to 290 nm. The chloromethoxy radicals formed in reaction 1 produce hydroperoxy radicals via reaction with molecular oxygen (CH2ClO + O2 --> HO2 + CHClO (2)). These hydroperoxy radicals are removed via reaction 3 and by their self-reaction (HO2 + HO2 --> H2O2 + O2 (4)). Unlike the majority of systems studied to date, the rate constant for the RO2 + HO2 reaction is not significantly faster than that for the RO2 + RO2 reaction and significant transient concentrations of HO2 are produced. Consequently, the observed second-order rate constant for radical disappearance depends strongly on the monitoring wavelength, and UV absorption cross-section and values of k1 and k3 could only be obtained by an iterative process. Sensitivity analyses with respect to all model parameters on fitted rate constants were performed. Arrhenius fits to the data on k1 and k3 gave k1 = (1.95 +/- 0.16) X 10(-13) exp[(874 +/- 26)K/7]cm3 molecule-1 s-1 and k3 = (3.26 +/- 0.61) X 10(-13) exp[(822 +/- 63)K/T] cm3 molecule-1 s-1. Average absolute uncertainties in k1 and k3 over the temperature range studied, including experimental scatter and uncertainties in the analysis parameters, were estimated to be 31 and 33%, respectively. The UV absorption spectrum of the chloromethylperoxy radical is typical of the spectra of alkylperoxy radicals, peaking at 230 nm, where sigma = (4.06 +/- 0.53) X 10(-18) cm2 molecule-1. In sharp contrast to the behavior of fully halogenated methylperoxy radicals, there was no evidence for the elimination of a chlorine atom from the chloromethoxy radical, CH2ClO, even at the highest temperature employed in this study. Semiempirical MNDO calculations and RRKM calculations were performed which suggest that unimolecular elimination of HCl from CH2ClO is important at high temperatures.

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