Question

Complete the following reaction: \[ \text{C}_6\text{H}_5\text{N}_2^+Cl^- \xrightarrow{\text{(i) HBF}_4} \xrightarrow{\text{(ii) NaNO}_2/\text{Cu}, \Delta} \quad ? \]

Hint:

- The Balz-Schiemann reaction is used to introduce fluorine into the benzene ring. - The Sandmeyer reaction is used to introduce nitro (-NO\(_2\)) and other functional groups.

Answer 1

The given reaction follows the Sandmeyer and Balz-Schiemann reactions, leading to the formation of fluorobenzene and nitrobenzene.
Step 1: Balz-Schiemann Reaction (Fluorination) The first step involves treating benzene diazonium chloride with HBF\(_4\), forming benzene diazonium tetrafluoroborate. \[ \text{C}_6\text{H}_5\text{N}_2^+Cl^- + HBF_4 \rightarrow \text{C}_6\text{H}_5\text{N}_2^+BF_4^- \] On heating, it decomposes to form fluorobenzene: \[ \text{C}_6\text{H}_5\text{N}_2^+BF_4^- \xrightarrow{\Delta} \text{C}_6\text{H}_5F + N_2 + BF_3 \] Step 2: Sandmeyer Reaction (Nitration) The second step involves treating benzene diazonium chloride with NaNO\(_2\)/Cu, which replaces diazonium with a nitro (-NO\(_2\)) group, forming nitrobenzene. \[ \text{C}_6\text{H}_5\text{N}_2^+Cl^- + NaNO_2/Cu, \Delta \rightarrow \text{C}_6\text{H}_5NO_2 + N_2 \]