Kinetics of Gas-Phase Reactions of CH3OCH2CF3, CH3OCH3, CH3OCH2CH3, CH3CH2OCH2CH3, and CHF2CF2OCH2CF3 with NO3 Radicals at 298 K

Rate constants for the gas-phase reactions of CH3OCH2CF3 (k(1)), CH3OCH3 (k(2)), CH3OCH2CH3 (k(3)), and CH3CH2OCH2CH3 (k(4)) with NO3 radicals were determined by means of a relative rate method at 298 K. NO3 radicals were prepared by thermal decomposition of N2O5 in a 700-750 Torr N2O5/NO2/NO3/air gas mixture in a 1-m(3) temperature-control led chamber. The measured rate constants at 298 K were k(1) = (5.3 +/- 0.9) x 10(-18), k(2) = (1.07 +/- 0.10) x 10(-16), k(3) = (7.81 +/- 0.36) x 10(-16), and k(4) = (2.80 +/- 0.10) x 10(-15) cm(3) molecule(-1) s(-1). Potential energy surfaces for the NO3 radical reactions were computationally explored, and the rate constants of k(1)-k(5) were calculated according to the transition state theory. The calculated values of rate constants k(1)-k(4) were in reasonable agreement with the experimentally determined values. The calculated value of k(5) was compared with the estimate (k(5) < 5.3 x 10(-21) cm(3) molecule(-1) s(-1)) derived from the correlation between the rate constants for reactions with NO3 radicals (k(1)-k(4)) and the corresponding rate constants for reactions with OH radicals. We estimated the tropospheric lifetimes of CH3OCH2CF3 and CHF2CF2OCH2CF3 to be 240 and >2.4 x 10(5) years, respectively, with respect to reaction with NO3 radicals. The tropospheric lifetimes of these compounds are much shorter with respect to the OH reaction. (C) 2009 Wiley Periodicals, Inc. Int J Chem Kinet 41: 490-497, 2009