Atmospheric chemistry of dimethoxymethane (CH3OCH2OCH3): Kinetics and mechanism of its reaction with OH radicals and fate of the alkoxy radicals CH3OCHO(&middot)OCH3 and CH3OCH2OCH2O(&middot)

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 cm3 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 -CH3 end groups and 24% on the central -CH2- unit. The atmospheric fate of the alkoxy radicals CH3OCH2OCH2O(&middot) and CH3OCHO(&middot)OCH3 at 296 K in 700 Torr of air was investigated using an FTIR-smog chamber technique. The sole atmospheric fate of CH3OCHO(&middot)OCH3 radicals is reaction with O2 to give dimethyl carbonate (CH3OC(O)OCH3) and HO2 radicals. At least three loss processes were identified for CH3OCH2OCH2O(&middot) radicals. In 1 atm of air at 295 K, 84±4% of the CH3OCH2OCH2O(&middot) radicals react with O2 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 CH3OCH2OCH3 and CH3OCH2OCHO of (1.4±0.2)×10-10 and (3.6±0.6)×10-11 cm3 molecule-1 s-1, respectively. Results are discussed in the context of the atmospheric chemistry of DMM.