TY - JOUR

T1 - Isotope Effects in the Reactions of Chloroform Isotopologues with Cl, OH and OD

AU - Nilsson, Elna Johanna Kristina

AU - Johnson, Matthew Stanley

AU - Nielsen, Claus J.

N1 - Paper id:: DOI: 10.1021/jp807233x

PY - 2009/2/10

Y1 - 2009/2/10

N2 - The kinetic isotope effects in the reactions of CHCl3, CDCl3, and 13CHCl3 with Cl, OH, and OD radicalshave been determined in relative rate experiments at 298 ( 1 K and atmospheric pressure monitored by longpath FTIR spectroscopy. The spectra were analyzed using a nonlinear least-squares spectral fitting procedureincluding line data from the HITRAN database and measured infrared spectra as references. The followingrelative 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 reactionsare opposite to the trends for CH4 and CH3Cl reported in the literature. The origin of these differences wasinvestigated using electronic structure calculations performed at the MP2/aug-cc-PVXZ (X ) D, T, Q) levelof theory and are compared with previously calculated values for the other methane derivatives. TheBorn-Oppenheimer barrier heights to H abstraction are 12.2 and 17.0 kJ mol-1 at the CCSD(T)/aug-ccpVTZlevel of theory for OH and Cl, respectively. The reaction rate coefficients of the two elementary vaporphase reactions including the 2H and 13C kinetic isotope effects were calculated using improved canonicalvariational theory with small curvature tunneling (ICVT/SCT) and the results compared with experimentaldata.

AB - The kinetic isotope effects in the reactions of CHCl3, CDCl3, and 13CHCl3 with Cl, OH, and OD radicalshave been determined in relative rate experiments at 298 ( 1 K and atmospheric pressure monitored by longpath FTIR spectroscopy. The spectra were analyzed using a nonlinear least-squares spectral fitting procedureincluding line data from the HITRAN database and measured infrared spectra as references. The followingrelative 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 reactionsare opposite to the trends for CH4 and CH3Cl reported in the literature. The origin of these differences wasinvestigated using electronic structure calculations performed at the MP2/aug-cc-PVXZ (X ) D, T, Q) levelof theory and are compared with previously calculated values for the other methane derivatives. TheBorn-Oppenheimer barrier heights to H abstraction are 12.2 and 17.0 kJ mol-1 at the CCSD(T)/aug-ccpVTZlevel of theory for OH and Cl, respectively. The reaction rate coefficients of the two elementary vaporphase reactions including the 2H and 13C kinetic isotope effects were calculated using improved canonicalvariational theory with small curvature tunneling (ICVT/SCT) and the results compared with experimentaldata.

M3 - Journal article

VL - 113

SP - 1731

EP - 1739

JO - Journal of Physical Chemistry Part A: Molecules, Spectroscopy, Kinetics, Environment and General Theory

JF - Journal of Physical Chemistry Part A: Molecules, Spectroscopy, Kinetics, Environment and General Theory

SN - 1089-5639

IS - 9

ER -