Carboxylic acid azides

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General formula of two mesomeric boundary structures of a carboxylic acid azide with the functional group marked in blue . R is an organyl radical ( alkyl radical, aryl radical, alkylaryl radical, etc.).

Carboxylic acid azides , also called acyl azides or acid azides, are a class of organic compounds in chemistry and are reactive carboxylic acid derivatives with the general structure R-CO-N 3 .

presentation

In the most common synthesis route, a carboxylic acid 1 is reacted with thionyl chloride (SOCl 2 ) to form the carboxylic acid chloride, which by adding sodium azide (NaN 3 ) leads to a carboxylic acid azide 2 . As with carboxylic acid chlorides, mixed carboxylic acid anhydrides can also be used as educt :

Carboxylic acid azide representation 1

Alternatively, a carboxylic acid 1 can be reacted with hydrazine (H 2 N-NH 2 ) to form the carboxylic acid hydrazide . Its diazotization also gives 2 :

Carboxylic acid azide preparation 2

Carboxylic acid azides can also be prepared by reacting carboxylic acids 1 with diphenylphosphoryl azide . However, due to the low atom economy , this reaction path is only useful on a laboratory scale.

properties

Carboxylic acid azides 2 are relatively unstable, sometimes explosive and very reactive compounds. They are therefore mostly used as synthesis intermediates, e.g. B. used in the Curtius reaction or in protein chemistry. Aliphatic carboxylic acid azides 2 (R = alkyl radical ) can usually not be isolated under normal conditions.

Individual evidence

  1. ^ J Weinstock: Modified Curtius reaction . In: J. Org. Chem. . 26, 1961, p. 3511. doi : 10.1021 / jo01067a604 .
  2. ^ V. Pozsgay, HJ Jennings: Azide synthesis with stable nitrosyl salts . In: Tetrahedron Lett. . 28, 1987, pp. 5091-5092. doi : 10.1016 / s0040-4039 (00) 95598-9 .
  3. ↑ Takayuki Shioiri, Kunihiro Ninomiya, Shunichi Yamada: Diphenylphosphoryl azide. New convenient reagent for a modified Curtius reaction and for peptide synthesis. In: Journal of the American Chemical Society. 94, No. 17, 1972, pp. 6203-6205, doi : 10.1021 / ja00772a052 .
  4. ^ Hans Beyer and Wolfgang Walter : Organic Chemistry . S. Hirzel Verlag, Stuttgart 1984, p. 254, ISBN 3-7776-0406-2 .