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.
Hermans
Ive
I
Department of Chemistry, Celestijnenlaan 200F, B-3001 Heverlee, Belgium.
Nguyen
Thanh L
TL
Jacobs
Pierre A
PA
Peeters
Jozef
J