Balz-Schiemann reaction
Fluorobenzene is made by treating benzene diazonium chloride with fluoroboric acid and heating the diazonium tetrafluoroborate that separates.
Benzene diazonium chlorideC₆H₅N₂⁺Cl⁻Diazonium salt - Step 1
(i) HBF₄ (ii) heat
FluorobenzeneC₆H₅FHaloarene
How it works
- Benzene diazonium chloride reacts with HBF₄ to give insoluble benzene diazonium tetrafluoroborate.
- On heating, the salt decomposes.
- Fluorobenzene, BF₃ and N₂ are the products.
What it makes
Fluorobenzene (direct fluorination of benzene is too violent to control).
Where it fails
Needs the dry diazonium tetrafluoroborate to be isolated and heated.
Class 12, Chapter 9 Amines
Balz-Schiemann reaction: quick answers
Why is fluorobenzene not made by the Sandmeyer reaction?
Fluorine is introduced through the diazonium tetrafluoroborate salt instead, which is the NCERT method for the fluoro compound.
What are the by-products of the Balz-Schiemann reaction?
Boron trifluoride and nitrogen.
Which reagent gives the insoluble salt?
Fluoroboric acid, HBF4.