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

Kinetics and mechanism for the gas-phase reaction of (CF3)(2)C = CH2 and OH radicals in the absence and presence of O-2/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)(2)C = CH2 molecule, and formed stable intermediates IM4 [(CF3)(2)C(OH)CH2)] and IM9[(CF3)(2)CC(OH)H-2)]. Other accessible products in the absence of O-2/NO were (CF3)(2)C = CH and H2O via the H-extraction reaction. In the atmosphere, IM4 and IM9 could further react with O-2/NO to form the likely main products (CF3)(2)CO, HCHO, (CF3)(2)C = CH, HO2 and (CF3)(2)C(OH)COH, in which (CF3)(2)CO and HCHO had been observed by experiment. The sole oxygen atom in (CF3)(2)CO or (CF3)(2)COCH2 was supplied by O-2 in atmosphere rather than OH radical. The rate constants for the feasible channels were in good agreement with the experimental datum. At 298 K, the atmospheric lifetime of similar to 50 days for (CF3)(2)C = CH2 demonstrates that (CF3)(2)C = CH2 has atmospherically persistent.

Automated summary

The gas-phase reaction of (CF3)(2)C = CH2 and OH radicals in the presence or absence of O-2/NO was investigated, revealing that OH radicals preferentially attack the C=C bond in (CF3)(2)C = CH2 molecule, forming stable intermediates. In the atmosphere, these intermediates further react with O-2/NO to produce main products observed in experiments.