Transhalogenation

Transhalogenation is a substitution reaction in which the halide of a halide compound is exchanged for another halide.^[1]

Finkelstein reaction

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]

Details and biological use

An enzyme-catalyzed transhalogenation.

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.^[2] Transhalogenation has been described as a gentle method for the synthesis of fluoroorganylboranes.^[4] It is also possible to produce aryliodides from the corresponding aryl chlorides or aryl bromides.^[5]

One investigation showed a possibility to perform transhalogenation by means of genetically modified enzymes (haloalkanes dehalogenases, HLDs).^[6]

Literature

• Yoel Sasson (2009-12-15). "Formation of Carbon-Halogen Bonds (Cl, Br, I)". PATai's Chemistry of Functional Groups. Chichester, UK: John Wiley & Sons, Ltd. pp. pat0011. doi:10.1002/9780470682531.pat0011. ISBN 978-0-470-68253-1. {{cite book}}: |periodical= ignored (help)
• "transhalogenation - Wiktionary". 27 October 2018.