Kochi reaction

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The Kochi reaction - named after the US chemist Jay Kochi (1927–2008) - is used to prepare secondary and tertiary hydrocarbon chlorides ( halogenated hydrocarbons ) from monocarboxylic acids . Therefore it is also rarely referred to as halodecarboxylation . The reaction takes place in the presence of lead tetraacetate as an oxidizing agent and calcium chloride or lithium chloride in boiling benzene . The carboxylic acid is oxidatively decarboxylated and reacted with the lithium chloride present to form the end product. By splitting off CO 2 ( decarboxylation ), the molecule is shortened by one carbon atom.

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Another variant is the Hunsdiecker reaction , in which some reaction steps follow a radical mechanism.

In another variant of the Kochi reaction according to Cyril A. Grob , the carboxylic acid is reacted with lead tetraacetate and N -chlorosuccinimide as chlorine donor in a mixture of dimethylformamide and glacial acetic acid . In particular, tertiary chlorides can be produced in this way with good yields and fewer by-products.

Practical meaning

The Kochi reaction is a purely laboratory process. Because of the formation of stoichiometric amounts of several waste materials - including a toxic lead salt - the atomic economy of the Kochi reaction is so bad that no industrial synthesis for secondary or tertiary halogenated hydrocarbons based on this reaction is realized industrially.

Individual evidence

  1. ↑ Hans Peter Latscha, Uli Kazmaier and Helmut Alfons Klein: Organic Chemistry: Basic Chemistry II . Springer Verlag Berlin; 5th edition 2002; ISBN 3-540-42941-7 ; P. 257.
  2. ↑ K. Becker, M. Geisel, C. Grob, F. Kuhnen: Improved Preparation of Tertiary Chlorides by Halodecarboxylation . In: Synthesis . tape 1973 , no. 08 , March 18, 2002, p. 493 , doi : 10.1055 / s-1973-22243 .

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