Computationally Efficient Methodology to Calculate C−H and C−X (X = F, Cl, and Br) Bond Dissociation Energies in Haloalkanes

A computationally efficient method for calculating C−H and C−X (X = F, Cl, and Br) bond dissociation energies in haloalkanes has been developed by determining correction factors to MP2/cc-pVtz energies. Corrections for basis set effects were determined by the difference in bond dissociation energies calculated at the MP2/cc-pVtz and MP2/cc-pV5z levels, and correlation effects were corrected by calculating the difference in energies at the MP2/cc-pVtz and CCSD(T)/cc-pVtz levels. Subsequent corrections for the spin−orbit energy of the atomic fragment and zero-point energy were applied to give a final bond dissociation energy. The correction factors were determined using CH 4, CH 3 F, CH 3 Cl, and CH 3 Br and are found to yield bond dissociation energies in excellent agreement with experimental results. This correction may also be broadly applied to multihalogen compounds, as shown in calculations of the C−H and C−X bond dissociation energies of CH 2 X 2 and CHX 3 (X = F, Cl, and Br) compounds, which accurately reproduce experimental values.