High Accuracy Measurements of OH Reaction Rate Constants and IR Absorption Spectra: Substituted 2-Propanols

Rate constants for the gas phase reactions of OH radicals with 2-propanol and three fluorine substituted 2-propanols, (CH₃)₂CHOH (k₀), (CF₃)₂CHOH (k₁), (CF₃)₂C(OH)CH₃ (k₂), and (CF₃)₃COH (k₃), were measured using a flash photolysis resonance-fluorescence technique over the temperature range 220−370 K. The Arrhenius plots were found to exhibit noticeable curvature for all four reactions. The temperature dependences of the rate constants can be represented by the following expressions: k₀(T) = 1.46 × 10⁻¹¹ × exp{−883/T} + 1.30 × 10⁻¹² × exp{+371/T} cm³molecule⁻¹s⁻¹; k₁(T) = 1.19 × 10⁻¹² × exp{−1207/T} + 7.85 × 10⁻¹⁶ exp{+502/T } cm³molecule⁻¹s⁻¹; k2(T) = 1.68 × 10−12 × exp{−1718/T} + 7.32 × 10−16 × exp{+371/T} cm³molecule⁻¹s⁻¹; k3(T) = 3.0 × 10−20 × (T/298)^11.3 × exp{+3060/T} cm³molecule⁻¹s⁻¹. The atmospheric lifetimes due to reactions with tropospheric OH were estimated to be 2.4 days and 1.9, 6.3, and 46 years, respectively. UV absorption cross sections were measured between 160 and 200 nm. The IR absorption cross sections of the three fluorinated compounds were measured between 450 and 1900 cm⁻¹, and their global warming potentials were estimated.