An ab Initio Study of the Kinetics of the Reactions of Halomethanes with the Hydroxyl Radical. 2. A Comparison between Theoretical and Experimental Values of the Kinetic Parameters for 12 Partially Halogenated Methanes

Ab initio calculations have been performed for the H-atom abstraction reactions from a series of 12 halogenated methanes by the hydroxyl radical. Geometry optimization and vibrational frequency calculations were performed for reactants, transition states, and products at the MP2/6-311G(2d,2p) level of theory. Single-point energy calculations were carried out at the PMP4(SDTQ) level with both 6-311G(3df,2p) and 6-311++G(3df,3pd) basis sets. Canonical transition state theory with Wigner's tunneling correction was used to predict the rate constants as function of the temperature (250−400 K). It is found that the treatment of the kinetics of these reactions with the lower level of theory, PMP4(SDTQ)/6-311G(3df,2p)//MP2/6-311G(2d,2p), leads to results in good agreement with experimental values and suggests the possibility of using this methodology in the implementation of a theoretical tool that properly describes the kinetics of reactions such as hydrogen abstractions by OH radicals from partially halogenated organic compounds.