Atmospheric chemistry of cyc–CF2CF2CX=CX– (X=H, F): Kinetics, products, and mechanism of gas–phase reactions with OH radicals, and atmospheric implication

Abstract

Rate constants for gas-phase reactions of series of hydrofluorocyclobutene including 3,3,4,4-tetrafluorocyclobutene (HFO-c1334zz), 1,3,3,4,4-pentafluorocyclobutene (HFO-c1325yz), and hexafluorocyclobutene (PFO-c1316) with OH radicals were assessed by a relative rate method. The values were determined as (8.47 ± 1.96) × 10⁻¹³ exp[(–475 ± 68)/T], (5.37 ± 0.99) × 10⁻¹³ exp[(–643 ± 53)/T] and (8.41 ± 2.24) × 10⁻¹³ exp[(–905 ± 78)/T] between 253 and 328 K; and 1.77 × 10⁻¹³, 0.644 × 10⁻¹³, and 0.402 × 10⁻¹³ cm³ molecule⁻¹ s⁻¹ at 298K, respectively. The atmospheric lifetimes were 65, 180, and 288 days, while their radiative efficiency (RE) were evaluated to be 0.088, 0.174, and 0.228 W m⁻² ppb⁻¹, respectively. The 100-year time horizon global warming potentials (GWP₁₀₀) were estimated to be 6, 31, and 65, respectively. The calculated POCP_E values of HFO-c1334zz, HFO-c1325yz, and PFO-c1316 were then obtained as 1.719 and 0.688 for North-west European and USA urban conditions, 0.579 and 0.222 for North-west European and USA urban conditions, and 0.324 and 0.124 for North-west European and USA urban conditions, respectively. Furthermore, the products and mechanism for the OH radical-initiated oxidation reactions of HFO-c1334zz, HFO-c1325yz, and PFO-c1316 were studied for the first time. COF₂, CO, and CO₂ were identified as the main carbon-containing products of HFO-c1334zz, HFO-c1325yz. Additionally, COF₂, CO₂, CO, and FC(O)OH were observed as the main products of PFO-c1316.