To obtain more accurate electronic energies, the lowest energy conformer is re-calculated with the Gaussian 4 (G4) compound method 41 in Gaussian 16. The G4 method was selected because it is an economical composite scheme that is accurate for halogenated hydrocarbons. Lastly, to obtain thermochemistry in NASA polynomial form, the G4 energies and harmonic frequencies and the DFT rotor scans are passed to RMG's statistical mechanics calculator Arkane, 44 a tool which uses quantum chemistry calculation results to compute thermochemical or kinetic parameters. For species with internal rotors, Arkane's best fit algorithm is used to determine whether a cosine function or a Fourier series better fits the energy profile of the rotor scan.