The atmospheric oxidation of ethyl formate and ethyl acetate over a range of temperatures and oxygen partial pressures

In both cases, Cl-atom attack at the CH₂ group is most important, leading in part to the formation of radicals of the type RC(O)OCH(O•)CH₃ [R = H, CH₃].

The atmospheric fate of these radicals involves competition between reaction with O2 to produce an anhydride compound, RC(O)OC(O)CH3, and the so-called α-ester rearrangement that produces an organic acid, RC(O)OH, and an acetyl radical, CH₃C(O). For both species studied, the α-ester rearrangement is found to dominate in air at 1 atm and 298 K. Barriers to the rearrangement of 7.7 ± 1.5 and 8.4 ± 1.5 kcal/mole are estimated for CH₃C(O)OCH(O•)CH₃ and HC(O)OCH(O•)CH₃, respectively, leading to increased occurrence of the O₂ reaction at reduced temperature.