Kinetic isotope effects in the gas phase reactions of OH and Cl with CH₃Cl, CD₃Cl, and ¹³CH₃Cl

The kinetic isotope effects in the reactions of CH₃Cl, ¹³CH₃Cl and CD₃Cl with OH radicals and Cl atoms were studied in relative rate experiments at 298&plusmn;2 K and 1013&plusmn;10 mbar. The reactions were carried out in a smog chamber using long path FTIR detection and the spectroscopic data analyzed employing a non-linear least squares spectral fitting method using measured high-resolution infrared spectra as well as absorption cross sections from the HITRAN database. The reaction rates of ¹³CH₃Cl and CD₃Cl with OH and Cl were determined relative to CH₃Cl as: <i>k</i>_OH+CH3Cl<i>k</i>_OH+CH3Cl/<i>k</i>_OH+13CH3Cl}<i>k</i>_OH+13CH3Cl=1.059&plusmn;0.008, <i>k</i>_OH+CH3Cl<i>k</i>_OH+CH3Cl/<i>k</i>_OH+CD3Cl<i>k</i>_OH+CD3Cl=3.9&plusmn;0.4, <i>k</i>_Cl+CH3Cl<i>k</i>_Cl+CH3Cl/<i>k</i>_Cl+13CH3Cl<i>k</i>_Cl+13CH3Cl =1.070&plusmn;0.010 and <i>k</i>_Cl+CH3Cl<i>k</i>_Cl+CH3Cl/<i>k</i>_Cl+CD3Cl<i>k</i>_Cl+CD3Cl=4.91&plusmn;0.07. The uncertainties given are 2&sigma; from the statistical analyses and do not include possible systematic errors. The unexpectedly large ¹³C kinetic isotope effect in the OH reaction of CH₃Cl has important implications for the global emission inventory of CH₃Cl