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 react ions from a series of 12 halogenated methanes by the hydroxyl radical. Geom etry 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(SD TQ) level with both 6-311G(3df,2p) and 6-311++G(3df,3pd) basis sets. Canoni cal transition state theory with Wigner's tunneling correction was used to predict the rate constants as function of the temperature (250-400 K). It i s found that the treatment of the kinetics of these reactions with the lowe r level of theory, PMP4(SDTQ)/6-911G(3df,2p)//MP2/6-311G(2d,2p), leads to r esults in good agreement with experimental values and suggests the possibil ity of using this methodology in the implementation of a theoretical tool t hat properly describes the kinetics of reactions such as hydrogen abstracti ons by OH radicals from partially halogenated organic compounds.