A liquid phase process is disclosed for producing halogenated alkane adducts of the formula CAR1R2CBR3R4 (where A, B, R1, R2, R3, and R4 are as defined in the specification) which involves contacting a corresponding halogenated alkane, AB, with a corresponding olefin, CR1R2═CR3R4 in a dinitrile or cyclic carbonate ester solvent which divides the reaction mixture into two liquid phases and in the presence of a catalyst system containing (i) at least one catalyst selected from monovalent and divalent copper; and optionally (ii) a promoter selected from aromatic or aliphatic heterocyclic compounds which contain at least one carbon-nitrogen double bond in the heterocyclic ring. When hydrochlorofluorocarbons are formed, the chlorine content may be reduced by reacting the hydrochlorofluorocarbons with HF.Azeotropes of CClF2CH2CF3 with HF and azeotropes of CF3CH2CHF2 with HF are also disclosed; as are process for producing such azeotropes.