Rates of the reactions of 111-trichloroethane (methyl chloroform) and 112-trichloroethane with OH

Highly purified samples of the two chlorocarbons were reacted with OH over the temperature range 278 to 460 K in a discharge‐flow system with resonance fluorescence detection of OH. Arrhenius expressions within 95% confidence limitsnot including systematic errorsare (5.49 ± 1.40) × 10−12 exp[−(1832 ± 98)/T] cm³ s−1 for CH3CCl3 and (1.57 ± 0.20) × 10−12 exp[−(463 ± 46)/T] cm³ s−1 for CH2ClCHCl2. The important methyl chloroform reaction is slower and its temperature dependence somewhat steeper than earlier measurements had indicatedpresumably due to the presence of faster reacting olefinic impurities in prior studies. Implications for stratospheric ozone reduction by ClOx catalysis and for the tropospheric OH‐budget are discussed briefly.