Transhalogenation

Transhalogenation (also: halide metathesis) is a substitution reaction in which a halogen atom of a halogen compound is exchanged for another halogen atom, for example the reaction of an alkyl chloride to an alkyl fluoride by means of sodium fluoride:

R-Cl + NaF → R-F + NaCl

If the halogen compound is an organic compound, this is called Finkelstein reaction.[1] 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.[2]

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.[1] Transhalogenation has been described as a gentle method for the synthesis of fluoroorganylboranes.[3] It is also possible to produce aryliodides from the corresponding aryl chlorides or aryl bromides.[4]

One investigation showed a possibility to perform transhalogenation by means of genetically modified enzymes (haloalkanes dehalogenases, HLDs).[5]

Literature
  • Yoel Sasson (2009-12-15). "Formation of Carbon-Halogen Bonds (Cl, Br, I)". PATai's Chemistry of Functional Groups. 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.
  • "transhalogenation - Wiktionary".

References
  1. Yoel Sasson (2009-12-15). "Formation of Carbon-Halogen Bonds (Cl, Br, I)". PATai's Chemistry of Functional Groups. 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.
  2. DE 68918542T, "Verfahren zur Transhalogenierung einer Halogenphosphor-Verbindung mit Fluorwasserstoff", published 1989-08-30
  3. Gerd Bir, Wolfgang Schacht, Dieter Kaufmann (1988-02-23), "Eine allgemeine, einfache und schonende Synthesemethode für Fluororganylborane", Journal of Organometallic Chemistry (in German), 340 (3), pp. 267–271, doi:10.1016/0022-328X(88)80020-2, ISSN 0022-328XCS1 maint: multiple names: authors list (link)
  4. Alex C. Bissember, Martin G. Banwell (2009-07-03), "Microwave-Assisted Trans-Halogenation Reactions of Various Chloro-, Bromo-, Trifluoromethanesulfonyloxy- and Nonafluorobutanesulfonyloxy-Substituted Quinolines, Isoquinolines, and Pyridines Leading to the Corresponding Iodinated Heterocycles†", The Journal of Organic Chemistry, 74 (13), pp. 4893–4895, doi:10.1021/jo9008386, ISSN 0022-3263, PMID 19480440
  5. Andy Beier, Jiri Damborsky, Zbynek Prokop (2019-04-17), "Transhalogenation Catalysed by Haloalkane Dehalogenases Engineered to Stop Natural Pathway at Intermediate", Advanced Synthesis & Catalysis, pp. adsc.201900132, doi:10.1002/adsc.201900132, ISSN 1615-4150CS1 maint: multiple names: authors list (link)
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