Atmospheric oxidation chemistry of hexafluoroisobutylene initiated by OH radical: Kinetics and mechanism

Abstract

Abstract Kinetics and mechanism for the gas-phase reaction of (CF3)2C\xa0=\xa0CH2 and OH radicals in the absence and presence of O2/NO have been investigated by G3(MP2)//B3PW91/6-311++G(d,p) method. The results showed the OH radical favored to attack the C C bond in (CF3)2C\xa0=\xa0CH2 molecule, and formed stable intermediates IM4[(CF3)2C(OH)CH2)] and IM9[(CF3)2CC(OH)H2)]. Other accessible products in the absence of O2/NO were (CF3)2C\xa0=\xa0CH and H2O via the H-extraction reaction. In the atmosphere, IM4 and IM9 could further react with O2/NO to form the likely main products (CF3)2CO, HCHO, (CF3)2C\xa0=\xa0CH, HO2 and (CF3)2C(OH)COH, in which (CF3)2CO and HCHO had been observed by experiment. The sole oxygen atom in (CF3)2CO or (CF3)2COCH2 was supplied by O2 in atmosphere rather than OH radical. The rate constants for the feasible channels were in good agreement with the experimental datum. At 298\xa0K, the atmospheric lifetime of ~50\xa0days for (CF3)2C\xa0=\xa0CH2 demonstrates that (CF3)2C\xa0=\xa0CH2 has atmospherically persistent.