Diazonium salts

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Diazonium salts (selection)
Structural formula of phenyldiazonium chloride
Phenyldiazonium chloride
( aromatic diazonium salt) is
somewhat stable in water at 0 ° C
Structural formula of methanediazonium chloride
Methanediazonium chloride
( aliphatic diazonium salt)
very unstable

Diazonium salts are a class of organic-chemical compounds with the general structural formula Ar – N 2 + X - . Ar stands for an organic , aromatic aryl group and X - stands for an unspecified anion . The simplest representatives of this group of substances are the phenyldiazonium salts, which are reasonably stable at low temperatures. Aliphatic diazonium salts are unstable. When heated ( thermolysis ) or when irradiated ( photolysis ), carbenes are formed with the elimination of nitrogen (N 2 ) .


Aromatic diazonium salts can be prepared by diazotizing primary aromatic amines with nitrite in an acidic medium at low temperature.


Pure diazonium salts are unstable, sometimes explosive and can only be handled in an aqueous solution (at temperatures <5 ° C). When trying to keep the salts anhydrous, they break down explosively, but can be stabilized with sterically demanding anions and then isolated.

Aromatic diazonium salts (here the phenyldiazonium cation) are significantly more stable than aliphatic diazonium salts because of the possible mesomeric stabilization of the positive charge:

Selection of mesomeric boundary structures of the phenyldiazonium cation.


Individual evidence

  1. ^ Siegfried Hauptmann : Organische Chemie , Verlag Harri Deutsch, 1985, p. 531, ISBN 3-87144-902-4 .