Kinetics of gas-phase reactions of CH3OCH2CF3, CH3OCH3, CH3OCH2CH3, CH3CH2OCH2CH3, and CHF2CF2OCH2CF3 with NO3 radicals at 298 K

✍ Scribed by L. Chen; T. Uchimaru; S. Kutsuna; K. Tokuhashi; A. Sekiya; H. Okamoto

• Publisher: John Wiley and Sons
• Year: 2009
• Tongue: English
• Weight: 215 KB
• Volume: 41
• Category: Article
• ISSN: 0538-8066
• DOI: 10.1002/kin.20425

✦ Synopsis

Abstract

Rate constants for the gas‐phase reactions of CH~3~OCH~2~CF~3~ (k~1~), CH~3~OCH~3~ (k~2~), CH~3~OCH~2~CH~3~ (k~3~), and CH~3~CH~2~OCH~2~CH~3~ (k~4~) with NO~3~ radicals were determined by means of a relative rate method at 298 K. NO~3~ radicals were prepared by thermal decomposition of N~2~O~5~ in a 700–750 Torr N~2~O~5~/NO~2~/NO~3~/air gas mixture in a 1‐m^3^ temperature‐controlled chamber. The measured rate constants at 298 K were k~1~ = (5.3 ± 0.9) × 10^−18^, k~2~ = (1.07 ± 0.10) × 10^−16^, k~3~ = (7.81 ± 0.36) × 10^−16^, and k~4~ = (2.80 ± 0.10) × 10^−15^ cm^3^ molecule^−1^ s^−1^. Potential energy surfaces for the NO~3~ 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 × 10^−21^ cm^3^ molecule^−1^ s^−1^) derived from the correlation between the rate constants for reactions with NO~3~ radicals (k~1~–k~4~) and the corresponding rate constants for reactions with OH radicals. We estimated the tropospheric lifetimes of CH~3~OCH~2~CF~3~ and CHF~2~CF~2~OCH~2~CF~3~ to be 240 and >2.4 × 10^5^ years, respectively, with respect to reaction with NO~3~ radicals. The tropospheric lifetimes of these compounds are much shorter with respect to the OH reaction. © 2009 Wiley Periodicals, Inc. Int J Chem Kinet 41: 490–497, 2009