A process is disclosed for reducing the mole ratio of (1) compounds of the formula Y1Y2C═CF2 wherein Y1 and Y2 are each independently H, F, Cl, Br, C1-C6 alkyl or C1-C6 haloalkyl containing no more than 3 chlorine substituents, 2 bromine substituents and 1 iodo substituent to (2) saturated compounds of the formula CdHeFfClgBrhIk wherein d is an integer from 1 to 10, and e+f+g+h+k is equal to 2d+2, provided that g is 0, 1, 2 or 3, h is 0, 1 or 2 and k is 0 or 1 and/or unsaturated compounds of the formula Y3Y4C═CY5Y6, wherein Y3, Y5 and Y6 are each independently H, F, Cl, Br, C1-C6 alkyl or C1-C6 haloalkyl containing no more than 3 chlorine substituents, 2 bromine substituents and 1 iodo substituent, provided that Y5 and Y6 are not both F, and Y4 is C1-C6 alkyl or C1-C6 haloalkyl containing no more than 3 chlorine substituents, 2 bromine substituents and 1 iodo substituent, in a mixture. The process involves contacting the mixture with at least one selective removal agent selected from the group consisting of SO3 and RSO3H, wherein R is selected from the group consisting of F, Cl, OH, C1-C8 alkyl, C1-C8 fluoroalkyl, and C1-C8 fluoroalkoxyalkyl containing no more than two ether oxygens to selectively react the formula Y1Y2C═CF2 compounds.