A study of the kinetics and products obtained from the reactions of 3-methylfuran with the main atmospheric oxidants has been performed. The rate coefficients for the gas-phase reaction of 3-methylfuran with OH and NO₃ radicals have been determined at room temperature and atmospheric pressure (air and N₂ as bath gases), using a relative method with different experimental techniques. The rate coefficients obtained for these reactions were (in units cm³ molecule⁻¹ s⁻¹) <i>k</i>_OH = (1.13 &plusmn; 0.22) &times; 10⁻¹⁰ and <i>k</i>_NO₃ = (1.26 &plusmn; 0.18) &times; 10⁻¹¹. Products from the reaction of 3-methylfuran with OH, NO₃ and Cl atoms in the absence and in the presence of NO have also been determined. The main reaction products obtained were chlorinated methylfuranones and hydroxy-methylfuranones in the reaction of 3-methylfuran with Cl atoms, 2-methylbutenedial, 3-methyl-2,5-furanodione and hydroxy-methylfuranones in the reaction of 3-methylfuran with OH and NO₃ radicals and also nitrated compounds in the reaction with NO₃ radicals. The results indicate that, in all cases, the main reaction path is the addition to the double bond of the aromatic ring followed by ring opening in the case of OH and NO₃ radicals. The formation of 3-furaldehyde and hydroxy-methylfuranones (in the reactions of 3-methylfuran with Cl atoms and NO₃ radicals) confirmed the H-atom abstraction from the methyl group and from the aromatic ring, respectively. This study represents the first product determination for Cl atoms and NO₃ radicals in reactions with 3-methylfuran. The reaction mechanisms and atmospheric implications of the reactions under consideration are also discussed

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The rate constants for the gas-phase reactions of the NO3 radical with a series of unsaturated aldehydes (acrolein, crotonaldehyde, trans-2-pentenal, trans-2-hexenal, trans-2-heptenal, and cis-4-heptenal) have been measured directly using a flow tube system coupled to a laser-induced fluorescence (LIF) detection system where the NO3 radical was monitored. The kinetic study was conducted in the temperature range from 298 to 433 K to investigate the temperature dependence of these reactions. This work is the first temperature-dependence study for the reactions of the nitrate radical with the above-mentioned aldehydes. The measured room-temperature rate constants for the reaction of NO3 with such unsaturated compounds (in units of 10-14 cm3 molecule-1 s-1) are as follows:  acrolein, 0.25 ± 0.04; crotonaldehyde, 1.61 ± 0.19; trans-2-pentenal, 2.88 ± 0.29; trans-2-hexenal, 5.49 ± 0.95; trans-2-heptenal, 9.59 ± 0.19; cis-4-heptenal, 26.40 ± 0.40. The proposed Arrhenius expressions for such reactions of NO3 are, respectively, k 1 = (1.7 ± 3.2) × 10-11 exp[−(3232 ± 355)/T] (cm3 molecule-1 s-1), k 2 = (5.52 ± 0.82) × 10-11 exp[−(2418 ± 57)/T] (cm3 molecule-1 s-1), k 3 = (5.4 ± 0.3) × 10-12 exp[−(1540 ± 200)/T] (cm3 molecule-1 s-1), k 4 = (1.20 ± 0.3) × 10-11 exp[−(926 ± 85)/T] (cm3 molecule-1 s-1), k 5 = (0.8 ± 0.2) × 10-12 exp[−(632 ± 47)/T] (cm3 molecule-1 s-1), and k 6 = (0.2 ± 0.1) × 10-11 exp[−(657± 6.0)/T] (cm3 molecule-1 s-1). Tropospheric lifetimes for these aldehydes have been calculated at night and during the daytime for typical NO3 and OH concentrations showing that both radicals provide an effective tropospheric sink for these compounds and that the night-time reaction with NO3 radical can be an important loss process for these emitted organics and for the NO3 radicals. The present work aims to evaluate the importance of these reactions in the atmosphere and to contribute new data to the study of NO3 reactivity.

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The absolute rate coefficients for the tropospheric reactions of hydroxyl radical (OH) with a series of linear aliphatic ketones (2-butanone (k1), 2-pentanone (k2), 2-hexanone (k3), and 2-heptanone (k4)) were measured as a function of temperature (228-405 K) and pressure (45-600 Torr of He) by the pulsed laser photolysis/laser induced fluorescence technique. These studies are essential to model the atmospheric chemistry of these ketones and their impact in the air quality. No pressure dependence of the rate coefficients was observed in the range studied. Thus, k1(298 K) (x10(-12) cm3 molecule(-1) s(-1)) were averaged over the pressure range studied yielding the following: (1.04+/-0.74), (3.14+/-0.40), (6.37+/-1.40), and (8.22+/-1.10), for 2-butanone (k1), 2-pentanone (k2), 2-hexanone (k3), and 2-heptanone (k4), respectively. k1 exhibits a slightly positive temperature dependence over the temperature range studied. A conventional Arrhenius expression describes the observed behavior. In contrast, the temperature dependence of k2-k4 shows a distinct deviation from the Arrhenius behavior. The best fit to our data was found to be described by the three-parameter expression: k(T) = A + B exp(-C/T) in cm3 molecule(-1) s(-1). This work constitutes the first determination of the temperature dependence of k2-k4. Our results are compared with previous studies, when possible, and are discussed in terms of the H-abstraction by OH radicals. The atmospheric implications of these reactions are also discussed.