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High-Accuracy Measurements of OH• Reaction Rate Constants and IR and UV...

Orkin, V. L., V. G. Khamaganov, L. E. Martynova, and M. J. Kurylo (2011), High-Accuracy Measurements of OH• Reaction Rate Constants and IR and UV Absorption Spectra: Ethanol and Partially Fluorinated Ethyl Alcohols, J. Phys. Chem. A, 115, 8656-8668, doi:10.1021/jp202099t.

Rate constants for the gas phase reactions of OH• radicals with ethanol and three fluorinated ethyl alcohols, CH3CH2OH (k0), CH2FCH2OH (k1), CHF2CH2OH (k2), and CF3CH2OH (k3) were measured using a flash photolysis resonance-fluorescence technique over the temperature range 220 to 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 over the indicated temperature intervals: k0(220-370 K) = 5.98 × 10-13 × (T/298)1.99 × exp(+515/T) cm3molecule−1s−1, k0(220-298 K) = (3.35 ± 0.06) × 10-12 cm3molecule−1s−1 [for atmospheric modeling purposes, k0(T) is essentially temperature-independent below room temperature], k1(230-370 K) = 3.47 × 10-14 ×(T/298)4.49 × exp(+977/T) cm3molecule−1s−1, k2(220-370 K) = 3.87 × 10-14 × (T/298)4.25 × exp(+578/T) cm3molecule−1s−1, and k3(220-370 K) = 2.48 × 10-14 × (T/298)4.03 × exp(+418/T) cm3molecule−1s−1. The atmospheric lifetimes due to reactions with tropospheric OH• were estimated to be 4, 16, 62, and 171 days, respectively, under the assumption of a well-mixed atmosphere. UV absorption cross sections of all four ethanols were measured between 160 and 215 nm. The IR absorption cross sections of the three fluorinated ethanols were measured between 400 and 1900 cm-1, and their global warming potentials were estimated.

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Upper Atmosphere Research Program (UARP)