ATMOSPHERIC CHEMISTRY OF DIMETHOXYMETHANE (CH3OCH2OCH3) - KINETICS AND MECHANISM OF ITS REACTION WITH OH RADICALS AND FATE OF THE ALKOXY RADICALS CH3OCHO(CENTER-DOT)OCH3 AND CH3OCH2OCH2O(CENTER-DOT)

The rate constant for the reaction of dimethoxymethane (DMM) with OH r adicals was determined to be (4.6 +/- 1.6) x 10(-12) at 346 +/- 3 K us ing a pulse radiolysis/transient UV absorption absolute rate technique and (5.3 +/- 1.0) x 10(-12) cm(3) molecule(-1) s(-1) at 295 +/- 2 K u sing 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(. ) and CH3OCHO(.)OCH3 at 296 K in 700 Torr of air was investigated usin g an FTIR-smog chamber technique. The sole atmospheric fate of CH3OCHO (.)OCH3 radicals is reaction with O-2 to give dimethyl carbonate (CH3O C(O)OCH3) and HO2 radicals. At least three loss processes were identif ied for CH3OCH2OCH2O(.) radicals. In 1 atm of air at 295 K, 84 +/- 4% of the CH3OCH2OCH2O(.) radicals react with O-2 while 7 +/- 3% undergo H-atom elimination; the fate of the remaining 9% is unclear. OH radica l-initiated oxidation of DMM in 1 atm of air at 296 K results in a yie ld of 24% dimethyl carbonate and 69% methoxymethyl formate; the oxidat ion mechanism of the remaining 7% of DMM is unclear. Relative rate tec hniques were used to measure rate constants for the reaction of Cl ato ms with CH3OCH2OCH3 and CH3OCH2OCHO of (1.4 +/- 0.2) x 10(-10) and (3. 6 +/- 0.6) x 10(-11) cm(3) molecule(-1) s(-1), respectively. Results a re discussed in the context of the atmospheric chemistry of DMM.