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.

References

1. Hudlicky, Milos; Hudlicky, Tomas (1983). "Formation of carbon-halogen bonds". Halides, Pseudo-Halides and Azides: Part 2 (1983). pp. 1021–1172. doi:10.1002/9780470771723.ch3. ISBN 9780470771723.
2. 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)
3. DE 68918542T, "Verfahren zur Transhalogenierung einer Halogenphosphor-Verbindung mit Fluorwasserstoff", published 1989-08-30
4. Gerd Bir, Wolfgang Schacht, Dieter Kaufmann (1988-02-23), "Eine allgemeine, einfache und schonende Synthesemethode für Fluororganylborane", Journal of Organometallic Chemistry (in German), vol. 340, no. 3, pp. 267–271, doi:10.1016/0022-328X(88)80020-2, ISSN 0022-328X{{citation}}: CS1 maint: multiple names: authors list (link)
5. 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, vol. 74, no. 13, pp. 4893–4895, doi:10.1021/jo9008386, ISSN 0022-3263, PMID 19480440
6. Andy Beier, Jiri Damborsky, Zbynek Prokop (2019-04-17), "Transhalogenation Catalysed by Haloalkane Dehalogenases Engineered to Stop Natural Pathway at Intermediate", Advanced Synthesis & Catalysis, vol. 361, no. 11, pp. adsc.201900132, doi:10.1002/adsc.201900132, ISSN 1615-4150{{citation}}: CS1 maint: multiple names: authors list (link)