Finkelstein reaction

[6] Alkyl halides differ greatly in the ease with which they undergo the Finkelstein reaction.

Vinyl, aryl and tertiary alkyl halides are unreactive; as a result, the reaction of NaI in acetone can be used as a qualitative test to determine which of the aforementioned classes an unknown alkyl halide belongs to, with the exception of alkyl iodides, as they yield the same product upon substitution.

Below some relative rates of reaction (NaI in acetone at 60 °C):[7][8] The aromatic chlorides and bromides are not easily substituted by iodide, though they may occur when appropriately catalyzed.

The so-called "aromatic Finkelstein reaction" is catalyzed by copper(I) iodide in combination with diamine ligands.

[9] Nickel bromide and tri-n-butylphosphine have been found to be suitable catalysts as well.