We present variational transition state calculations of the rate constants for the CH2F2 + OH hydrogen abstraction reaction in the temperature range from 200 to 500 K. We have employed a dual-level approach to direct dynamics using the interpolated optimized corrections methodology. In the variational transition state calculations, tunneling has been included within the microcanonical optimized multidimensional scheme employing the recently developed LCG4 (large-curvature ground-state, version 4) approximation to evaluate the large curvature tunneling effects. At the QCISD(T)/6-311++G(2df,p)//QCISD/6-311G(d,p)[QCISD/631G(d)]///PM3 and the CCSD(T)//MP2/cc-pVTZ///PM3 levels, the classical energy barriers turn out to be, respectively, 5.8 and 5.1 kcal/mol. These calculations show significant variational effects at all temperatures. These direct dynamics approaches reproduce quite well the experimental rate constants from 500 to 250 K, and slightly overestimate them from 250 to 210 K. The disagreement at the low-temperature range needs of further analysis.
González-Lafont, A., Lluch, J. M., & Espinosa-García, J. (2001). Variational transition state calculations of the CH2F2 + OH hydrogen abstraction reaction. Journal of Physical Chemistry A, 105(46), 10553-10561. https://doi.org/10.1021/jp012648j