Conversion of benzene diazonium chloride to chlorobenzene is an example of which of the following reactions?

The conversion of benzene diazonium chloride to chlorobenzene involves replacing the diazonium group (−N₂⁺Cl⁻) with a chlorine atom. The reaction is:

$$C_{6}H_{5}N_{2}Cl -> C_{6}H_{5}Cl + N_{2}$$

Now, let's examine each option:

Option A: Claisen reaction - This typically refers to condensation or rearrangement reactions involving carbonyl compounds, such as esters forming β-keto esters. It does not apply to diazonium salt conversions.

Option B: Friedel-Crafts reaction - This is an electrophilic aromatic substitution where halogens or alkyl groups are introduced using catalysts like AlCl₃. For example, benzene reacts with Cl₂/AlCl₃ to form chlorobenzene. However, here we start from benzene diazonium chloride, not benzene, so this is incorrect.

Option C: Sandmeyer reaction - This reaction specifically converts aryl diazonium salts to aryl halides using copper(I) halides. For chlorobenzene, benzene diazonium chloride reacts with CuCl:

$$C_{6}H_{5}N_{2}Cl + CuCl -> C_{6}H_{5}Cl + N_{2} + CuCl$$

This matches the given conversion exactly.

Option D: Wurtz reaction - This couples alkyl halides with sodium metal to form higher alkanes (e.g., 2CH₃Br + 2Na → CH₃CH₃ + 2NaBr). It does not involve diazonium salts.

Therefore, the conversion is a Sandmeyer reaction.

Hence, the correct answer is Option C.