Atmospheric Chemistry of Dimethoxymethane (CH₃OCH₂OCH₃):  Kinetics and Mechanism of Its Reaction with OH Radicals and Fate of the Alkoxy Radicals CH₃OCHO(•)OCH₃ and CH₃OCH₂OCH₂O(•)

The rate constant for the reaction of dimethoxymethane (DMM) with OH radicals was determined to be (4.6 ± 1.6) × 10 -12 at 346 ± 3 K using a pulse radiolysis/transient UV absorption absolute rate technique and (5.3 ± 1.0) × 10 -12 cm 3 molecule -1 s -1 at 295 ± 2 K using an FTIR-smog chamber relative rate technique. The reaction of OH radicals with DMM occurs via an H-atom abstraction mechanism with 76% of the attack occurring on the −CH 3 end groups and 24% on the central −CH 2 − unit. The atmospheric fate of the alkoxy radicals CH 3 OCH 2 OCH 2 O(•) and CH 3 OCHO(•)OCH 3 at 296 K in 700 Torr of air was investigated using an FTIR-smog chamber technique. The sole atmospheric fate of CH 3 OCHO(•)OCH 3 radicals is reaction with O 2 to give dimethyl carbonate (CH 3 OC(O)OCH 3 ) and HO 2 radicals. At least three loss processes were identified for CH 3 OCH 2 OCH 2 O(•) radicals. In 1 atm of air at 295 K, 84 ± 4% of the CH 3 OCH 2 OCH 2 O(•) radicals react with O 2 while 7 ± 3% undergo H-atom elimination; the fate of the remaining 9% is unclear. OH radical-initiated oxidation of DMM in 1 atm of air at 296 K results in a yield of 24% dimethyl carbonate and 69% methoxymethyl formate; the oxidation mechanism of the remaining 7% of DMM is unclear. Relative rate techniques were used to measure rate constants for the reaction of Cl atoms with CH 3 OCH 2 OCH 3 and CH 3 OCH 2 OCHO of (1.4 ± 0.2) × 10 -10 and (3.6 ± 0.6) × 10 -11 cm 3 molecule -1 s -1, respectively. Results are discussed in the context of the atmospheric chemistry of DMM.