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

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  • Timothy J. Wallington
  • Michael D. Hurley
  • James C. Ball
  • Ann M. Straccia
  • Jesper Platz
  • Lene Krogh Christensen
  • Jens Sehested
  • Nielsen, Ole John

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(•) and CH3OCHO(•)OCH3 at 296 K in 700 Torr of air was investigated using an FTIR-smog chamber technique. The sole atmospheric fate of CH3OCHO(•)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(•) radicals. In 1 atm of air at 295 K, 84 ± 4% of the CH3OCH2OCH2O(•) 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.

OriginalsprogEngelsk
TidsskriftJournal of Physical Chemistry A
Vol/bind101
Udgave nummer29
Sider (fra-til)5302-5308
Antal sider7
ISSN1089-5639
StatusUdgivet - 17 jul. 1997

ID: 227487009