Name the reaction by which Freon 12 is manufactured

The correct answer is Option (2) → Swarts reaction

In the Swarts reaction, an alkyl chloride or bromide is heated with a metallic fluoride such as AgF, \( \ce{Hg2F2} \), \( \ce{CoF2} \) or \( \ce{SbF3} \), and the chlorine or bromine is replaced by fluorine. It is the usual way of making alkyl fluorides.

Freon-12 is dichlorodifluoromethane, \( \ce{CCl2F2} \). It is made from tetrachloromethane by replacing two chlorine atoms with fluorine:

    \( \displaystyle \ce{3CCl4 + 2SbF3 -> 3CCl2F2 + 2SbCl3} \)

So Freon-12 is synthesised from tetrachloromethane by the Swarts reaction.

Why the other options are incorrect

• Option (1) Wurtz-Fittig reaction — Incorrect. An alkyl halide and an aryl halide react with sodium in dry ether and join to give an alkylarene; no halogen exchange takes place.

      \( \displaystyle \ce{C6H5-X + R-X + 2Na} \xrightarrow{\text{dry ether}} \ce{C6H5-R + 2NaX} \)

• Option (3) Electrophilic substitution reaction — Incorrect. This puts a new group on an aromatic ring, as in the chlorination of benzene with \( \ce{Cl2} \)/anhydrous \( \ce{FeCl3} \). Freon-12 is a methane derivative with no ring, and its fluorine comes from a metallic fluoride.

• Option (4) Free radical halogenation — Incorrect. In light, chlorine replaces the hydrogen atoms of methane one by one through free radicals. This can give tetrachloromethane, but it cannot change its chlorine atoms into fluorine; that exchange needs a metallic fluoride.

NCERT (2026-27 edition):
Freons

Note: The same/similar question has been asked in different years by NTA as per the details given below: