Enthalpy changes corresponding to the gas phase heats of dissociation of 12 organic halides were calculated using two semiempirical methods, the Hartree-Fock method, and two DFT methods. These calculated values were compared to experimental values where possible. All five methods agreed generally with the expected empirically known trends in the dissociation of alkyl halides. Enthalpy changes were also calculated in aqueous solution and found to follow a very similar trend to the gas phase enthalpy changes. (Contains 2 tables.)