Tropopause chemistry revisited: HO2*-initiated oxidation as an efficient acetone sink.
Acetone is known to be a key species in the chemistry of the Upper Troposphere and Lower Stratosphere. In this theoretical study, using amply validated methodologies, the hitherto overlooked reaction of acetone with HO2* radicals is found to lead to a fast equilibrium (CH3)2C=O + HO2* right harpoon over left harpoon (CH3)2C(OH)OO*. At room temperature, this is shifted entirely to the left and thus of no consequence. However, near the tropopause (T </= 220 K), the equilibrium is shown to shift to the right to such an extent that the subsequent reaction of (CH3)2C(OH)OO* with (partly air-traffic-generated) NO becomes an effective acetone sink. This process finally results in acetic acid, thus explaining the great abundance of this important organic acid observed near the tropopause.
Department of Chemistry, Celestijnenlaan 200F, B-3001 Heverlee, Belgium.
Ive
I
Hermans
Thanh L
TL
Nguyen
Pierre A
PA
Jacobs
Jozef
J
Peeters