Hunsdiecker reaction
The Hunsdiecker reaction (also called Borodin reaction after the discoverer Alexander Borodin and Hunsdiecker-Borodin reaction ) is a name reaction in organic chemistry that was further developed by Heinz and Claire Hunsdiecker.
The Hunsdiecker reaction is a decarboxylation of carboxylic acid salts by treatment with halogens , with halogenated hydrocarbons being formed. Suitable metal salts of carboxylic acids can silver -, mercury - or thallium can be used (I) salts, and as halogen can chlorine , bromine or iodine are used.
mechanism
The silver salt is reacted with a halogen, silver halide being split off and hypohalite being formed. The halogen-oxygen bond is split homolytically into a halogen radical and a carboxyl radical which, after the release of CO 2, reacts further with a free halogen radical to form the halogenated hydrocarbon. By splitting off CO 2 ( decarboxylation ), the molecule is shortened by one carbon atom. Carbon tetrachloride is often used as a solvent. Some of the reaction steps proceed according to a radical mechanism. Its mechanism is thus similar to that of Kolbe electrolysis . In principle, both aliphatic and aromatic carboxylic acids can be used.
The silver salts required for this reaction can be obtained by reacting the corresponding carboxylic acids with silver oxide. Another variant of this reaction is halodecarboxylation , in which the carboxylic acid is reacted with lead (IV) acetate and calcium chloride or lithium chloride in boiling benzene ( Kochi reaction ).
Practical meaning
The Hunsdiecker reaction is a purely laboratory process. Because of the formation of stoichiometric amounts of several waste materials - including a heavy metal salt (e.g. silver salt) - the atomic economy of the Hunsdiecker reaction is so bad that no industrial synthesis for halogenated hydrocarbons based on this reaction is possible.
Individual evidence
- ^ A b c T. Laue, A. Plagens: Name and catchword reactions of organic chemistry . Teubner Verlag, 2006, ISBN 3-8351-0091-2 , p. 190-193 .
- ↑ L. Kürti, B. Czakó: Strategic Applications Of Named Reactions In Organic Synthesis . Elsevier Academic Press, USA 2005, pp. 218 .
- ↑ Latscha u. a .: Organic chemistry: Basic chemistry knowledge II. p. 125.
- ↑ Hans Peter Latscha, Uli Kazmaier, Helmut Alfons Klein: Organic Chemistry: Chemistry Basics II . 5th edition. Springer Verlag, Berlin 2002, ISBN 3-540-42941-7 , p. 257.