Transhalogenation is a substitution reaction in which the halide of a halide compound is exchanged for another halide.[1]
A common method is halide metathesis. An example is the conversion of alkyl chloride into alkyl fluoride:
C3H5-Cl + NaF → R-F + NaCl
This kind of reaction is called Finkelstein reaction.[2] However, it is also possible, for example, to produce phosphorus fluoride compounds by transhalogenating chlorine, bromine or iodine bound to phosphorus with a metal fluoride.[3]
As a halogen source for transhalogenation, metal halides (such as sodium fluoride or lithium fluoride) are often used, but also the use of onium halides is possible. Transhalogenation has been described as a gentle method for the synthesis of fluoroorganylboranes. It is also possible to produce aryliodides from the corresponding aryl chlorides or aryl bromides.
One investigation showed a possibility to perform transhalogenation by means of genetically modified enzymes (haloalkanes dehalogenases, HLDs).