Atmospheric Oxidation Mechanism of Methyl Propionate

Smog chamber FTIR techniques were used to study the atmospheric oxidation of methyl propionate in 740 Torr of air in the presence of NO x at 296 ± 2K. Relative rate techniques were used to measure k (OH + CH 3 CH 2 C(O)OCH 3 ) = (9.29 ± 1.13) × 10 -13, k (Cl + CH 3 CH 2 C(O)OCH 3 ) = (1.51 ± 0.22) × 10 -11, k (Cl + CH 3 CH 2 C(O)OC(O)H) = (2.89 ± 0.35) × 10 -12, k (Cl + CH 3 CH 2 C(O)OH) = (4.72 ± 0.62) × 10 -12, and k (Cl + CH 3 C(O)C(O)OCH 3 ) = (4.99 ± 0.96) × 10 -13 cm 3 molecule -1 s -1 . The products (and molar yields) formed in the Cl-atom initiated oxidation of methyl propionate were as follows: propionic formic anhydride (CH 3 CH 2 C(O)OC(O)H), 0.099 ± 0.019; propionic acid (CH 3 CH 2 C(O)OH), 0.139 ± 0.027; carbon monoxide, 0.132 ± 0.026; methyl pyruvate (CH 3 C(O)C(O)OCH 3 ), 0.289 ± 0.057; acetaldehyde, 0.077 ± 0.015; methoxy formylperoxynitrate (CH 3 OC(O)O 2 NO 2 ), 0.083 ± 0.016; methyl glyoxylate (H(O)CC(O)OCH 3 ), 0.111 ± 0.022; organic nitrates, 0.07 ± 0.02; and formaldehyde. These products account for 79 ± 16% of the loss of methyl propionate. The atmospheric oxidation mechanism of methyl propionate is presented and discussed.