Balz–Schiemann reaction

The Schiemann reaction, also called the Balz- Schiemann reaction, named after the German chemist Günther Schiemann, allows in a simple way, the introduction of fluorine substituents in an aromatic. These aryl diazonium tetrafluoroborate are heated in the solid, dry state or in an inert solvent to its decomposition. The Schiemann reaction replaces the outgoing and the diazonium salt Sandmeyer reaction, which is good for chlorination and bromination, but rather ill-suited for the fluorination.

General reaction equation

The synthesis is usually on a normal diazotization of the aromatic amine ( arylamine, in the simplest case of aniline: Ar = phenyl ) to Aryldiazoniumchlorid. By adding a sodium tetrafluoroborate solution ( Na [ BF4] ), the diazonium salt is precipitated as tetrafluoroborate, the precipitate is washed, dried, and heated gently for implementation. Aryl diazonium tetrafluoroborates are compared to the corresponding chlorides, which are highly explosive, relatively stable.