The products following Cl atom initiated oxidation of methyl formate in 700−760 Torr of air in the presence and absence of NO x at 296 ± 2 K were investigated using three different FTIR smog chamber techniques. Reaction of Cl atoms with methyl formate proceeds 45 ± 7% via attack at the methyl group (forming HC(O)OCH2· radicals) and 55 ± 7% via attack at the formate group (forming ·C(O)OCH3 radicals). The sole atmospheric fate of HC(O)OCH2· and ·C(O)OCH3 radicals is addition of O2 to give the corresponding peroxy radicals (HC(O)OCH2OO· and ·OOC(O)OCH3). The peroxy radicals react with NO to give alkoxy radicals (HC(O)OCH2O· and ·OC(O)OCH3). The atmospheric fate of ·OC(O)OCH3 radicals is decomposition to give CH3O· and CO2 and was unaffected by the method used to generate the ·OC(O)OCH3 radicals (reaction of ·OOC(O)OCH3 with either NO or with other peroxy radicals). There are two competing atmospheric loss mechanisms for HC(O)OCH2O· radicals; reaction with O2 to give HC(O)OC(O)H (formic acid anhydride) and α-ester rearrangement to give HC(O)OH and HCO· radicals. It was found that α-ester rearrangement is more important when HC(O)OCH2O· radicals were produced via the HC(O)OCH2OO· + NO reaction than when they were produced via the self-reaction of peroxy radicals. We ascribe this observation to the formation of vibrationally excited HC(O)OCH2O· radicals in the HC(O)OCH2OO· + NO reaction. In 1 atm of air ([O2] = 160 Torr) containing NO at 296 K, it can be calculated that 33 ± 5% of the HC(O)OCH2O· radicals undergo α-ester rearrangement, while 67 ± 12% react with O2. The infrared spectrum of the peroxynitrate CH3OC(O)OONO2 was recorded, and absorption cross sections (base e) of (1.8 ± 0.1) × 10-18 and (4.2 ± 0.2) × 10-18 cm2 molecule-1 at 1836 and 1236 cm-1, respectively, were determined. The chain chlorination of methyl formate was studied. Relative rate techniques were used to measure k(Cl +ClC(O)OCH3) = (1.10 ± 0.23) × 10-13, k(Cl + HC(O)OCH2Cl) = (2.5 ± 0.2) × 10-13, and k(Cl + ClC(O)OCH2Cl) = (3.0 ± 0.4) × 10-14 cm3 molecule-1 s-1. IR spectra of ClC(O)OCH2Cl, ClC(O)OCHCl2, and ClC(O)OCCl3 are presented. These results are discussed with respect to the atmospheric oxidation mechanism of methyl formate and other esters.

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A FTIR kinetic and product study of the OH-radical initiated oxidation of 1,4-dioxane (DOX) has been performed in a quartz-glass photoreactor in the laboratory under different conditions and also in the outdoor EUPHORE simulation chamber in Valencia, Spain. Using the relative kinetic technique, a rate coefficient of k = (1.24 ± 0.04) × 10-11 cm3 molecule-1 s-1 was determined for the reaction at 298 K in 1000 mbar of synthetic air, which is in good agreement with other published values. The major reaction product both in the presence and absence of NO was ethylene glycol diformate (EDF). This compound has been synthesized, and authentic samples have been used for calibration. Integrated band intensities have been calculated for the three strongest bands of EDF:  (4.99 ± 0.06) × 10-17 cm molecule-1 for 1100−1225 cm-1, (3.90 ± 0.05) × 10-17 cm molecule-1 for 1670−1820 cm-1, (9.34 ± 0.11) × 10-18 cm molecule-1 for 2775−3075 cm-1. In the laboratory reactor, yields for EDF of 87 ± 9 and 95 ± 10 mol % were obtained using the photolysis of MeONO/NO/air and H2O2/NO/air as the OH radical sources, respectively. Using only the photolysis of H2O2/air as the OH source resulted in a molar yield of 55 ± 6 mol % for EDF. In the outdoor EUPHORE simulation chamber a yield of 95 ± 10 mol % was obtained from irradiation of a DOX/NO x /air mixture. The OH-radical- and Cl-atom-initiated oxidation of EDF has also been investigated. Rate coefficients of k OH = (4.72 ± 0.31) × 10-13 cm3 molecule-1 s-1 and k Cl = (3.52 ± 0.09) × 10-12 cm3 molecule-1 s-1 have been determined for the reaction of EDF with OH radicals and Cl atoms, respectively, at 298 K and 1000 mbar total pressure. The products determined in the Cl-initiated oxidation in the presence of NO x were formic acid anhydride (FAA), formic acid (FA), and carbon monoxide (CO) with yields of 173 ± 34 mol %, 45 ± 9 mol %, and 41 ± 8 mol %, respectively. Formation of a peroxy formyl nitrate was also observed. In the absence of NO x the yields of FAA, FA and CO were 144 ± 29 mol %, 39 ± 8 mol %, and 22 ± 4 mol %, respectively.

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