Abstract
The kinetic isotope effects in the reactions of CHCl3, CDCl3, and 13CHCl3 with Cl, OH, and OD radicals
have been determined in relative rate experiments at 298 ( 1 K and atmospheric pressure monitored by long
path FTIR spectroscopy. The spectra were analyzed using a nonlinear least-squares spectral fitting procedure
including line data from the HITRAN database and measured infrared spectra as references. The following
relative reaction rates were determined: kCHCl3+Cl/kCDCl3+Cl ) 3.28 ( 0.01, kCHCl3+Cl/k13CHCl3+Cl ) 1.000 ( 0.003,
kCHCl3+OH/kCDCl3+OH ) 3.73 ( 0.02, kCHCl3+OH/k13CHCl3+OH ) 1.023 ( 0.002, kCHCl3+OD/kCDCl3+OD ) 3.95 ( 0.03,
and kCHCl3+OD/k13CHCl3+OD ) 1.032 ( 0.004. Larger isotope effects in the OH reactions than in the Cl reactions
are opposite to the trends for CH4 and CH3Cl reported in the literature. The origin of these differences was
investigated using electronic structure calculations performed at the MP2/aug-cc-PVXZ (X ) D, T, Q) level
of theory and are compared with previously calculated values for the other methane derivatives. The
Born-Oppenheimer barrier heights to H abstraction are 12.2 and 17.0 kJ mol-1 at the CCSD(T)/aug-ccpVTZ
level of theory for OH and Cl, respectively. The reaction rate coefficients of the two elementary vapor
phase reactions including the 2H and 13C kinetic isotope effects were calculated using improved canonical
variational theory with small curvature tunneling (ICVT/SCT) and the results compared with experimental
data.
have been determined in relative rate experiments at 298 ( 1 K and atmospheric pressure monitored by long
path FTIR spectroscopy. The spectra were analyzed using a nonlinear least-squares spectral fitting procedure
including line data from the HITRAN database and measured infrared spectra as references. The following
relative reaction rates were determined: kCHCl3+Cl/kCDCl3+Cl ) 3.28 ( 0.01, kCHCl3+Cl/k13CHCl3+Cl ) 1.000 ( 0.003,
kCHCl3+OH/kCDCl3+OH ) 3.73 ( 0.02, kCHCl3+OH/k13CHCl3+OH ) 1.023 ( 0.002, kCHCl3+OD/kCDCl3+OD ) 3.95 ( 0.03,
and kCHCl3+OD/k13CHCl3+OD ) 1.032 ( 0.004. Larger isotope effects in the OH reactions than in the Cl reactions
are opposite to the trends for CH4 and CH3Cl reported in the literature. The origin of these differences was
investigated using electronic structure calculations performed at the MP2/aug-cc-PVXZ (X ) D, T, Q) level
of theory and are compared with previously calculated values for the other methane derivatives. The
Born-Oppenheimer barrier heights to H abstraction are 12.2 and 17.0 kJ mol-1 at the CCSD(T)/aug-ccpVTZ
level of theory for OH and Cl, respectively. The reaction rate coefficients of the two elementary vapor
phase reactions including the 2H and 13C kinetic isotope effects were calculated using improved canonical
variational theory with small curvature tunneling (ICVT/SCT) and the results compared with experimental
data.
| Original language | English |
|---|---|
| Journal | Journal of Physical Chemistry A |
| Volume | 113 |
| Issue number | 9 |
| Pages (from-to) | 1731-1739 |
| Number of pages | 9 |
| ISSN | 1089-5639 |
| Publication status | Published - 10 Feb 2009 |