First Principle Studies on the Atmospheric Oxidation of HFC-C1436 Initiated by OH radical
The atmospheric oxidation mechanism and kinetics of 3, 3, 4, 4, 5, 5- hexafluorocyclopentene (HFC-C1436) initiated by OH radical has been investigated by using electronic structure calculations. Canonical variation transition state theory was employed to predict the rate constant for the favourable OH-addition reaction pathway. Under atmospheric condition, the initially formed HFC-C1436-OH adduct, reacts rapidly with O2 and NO• to form the peroxy and alkoxy radical, which subsequently react with HO2 and O2 to form 2,2,3,3,4,4-Hexafluoro-5-hydroperoxy-cyclopentanol (P1), 3,3,4,4,5,5-Hexafluoro-cyclopentane-1,2-diol (P2) and 2,2,3,3,4,4-Hexafluoro-5-hydroxy-cyclopentane (P3). Two different ring opening reaction pathways of alkoxy radical were studied. In addition to the products, P1, P2 and P3, the possible end products identified from ring opening reactions are CO, CO2, COF2 and glyoxal which will induce less environmental impacts than the chloroflurocarbons (CFC). The rate constant calculated for the favourable initial reaction at 298 K is 0.842 × 10−13 cm3molecule−1s−1 and is in agreement with the available experimental value. The atmospheric lifetime, global warming potentials (GWPs) for different time horizon and photochemical ozone creation potential (POCP) were also calculated.