Tropospheric Oxidation of 1H-Heptafluorocyclopentene (cyc-CF2CF2CF2CF=CH-) with OH Radicals: Reaction Mechanism, Kinetics, and Global Warming Potentials

Assessment of the atmospheric chemistry and environmental impact of 1H-heptafluorocyclopentene (i.e., cyc-CF2CF2CF2CF=CH) appears essential before its wide-scale applications. So, in this present work, we have investigated the (OH)-O-center dot radical-initiated oxidation of cyc-CF2CF2CF2CF=CH- using the density functional theory. We have used M11/6-311++G(d,p) level of theory for geometry optimization and frequency calculations. The energetics and rate constant calculations indicate that the pathway concerning the (OH)-O-center dot radical addition reaction with the C=C bond is more favorable than the H- and F-abstraction reactions with the (OH)-O-center dot radical. The canonical transition state theory has been employed to calculate the rate constant within the temperature range of 250-450 K and 1 atm pressure. The estimated overall rate constant value is 7.14 x 10(-14) cm(3) molecule(-1) s(-1) at 298.15 K, which agrees well with the previously reported experimental rate constant value of (5.20 +/- 0.09) x 10(-14) cm(3) molecule(-1) s(-1) at 298.15 K. Moreover, we have determined the branching ratio percentage and found that the (OH)-O-center dot radical addition reaction contributes 99.99% to the overall rate constant. The calculated atmospheric lifetime is 0.44 years. Furthermore, the radiative efficiency (RE) is determined to be 0.132 W m(-2) ppb(-1) and the photochemical ozone creation potential (POCPs) is also calculated as 0.82. Finally, global warming potentials (GWPs) for 20, 100, and 500 years are estimated as 67.77, 18.60, and 5.31, respectively.

Automated summary

The study investigated the oxidation of 1H-heptafluorocyclopentene through (OH)-O-center dot radical-initiated reactions using density functional theory, showing that the addition reaction is more favorable than abstraction reactions. The results suggest that the (OH)-O-center dot radical addition reaction contributes significantly to the overall rate constant, with atmospheric lifetime, radiative efficiency, and global warming potentials also estimated.