How many of the following compounds can be obtained from benzenediazo…

The correct answer is Option (2) → 3

All six compounds can be made from benzenediazonium chloride, because the diazonium group can be replaced by –F, –Cl, –Br, –I, –CN or –OH. The diazonium route is needed only for the compounds that cannot be made in the two usual ways: direct halogenation of benzene, or replacing the chlorine of chlorobenzene by a nucleophile.

Prepared neither way:

• Fluorobenzene (fluorine is highly reactive; made by heating benzenediazonium fluoroborate)

• Iodobenzene (iodine is not easily put into the ring directly; made with KI)

• Cyanobenzene (not from chlorobenzene; made with CuCN/KCN)

Can be prepared another way:

• Chlorobenzene — direct chlorination of benzene with anhydrous FeCl₃.

• Phenol — chlorobenzene fused with NaOH at 623 K and 320 atm, then acidified.

• Bromobenzene — direct bromination of benzene with iron or iron(III) bromide.

Prepared neither way: 3 compounds.

NCERT (2026-27 edition):
9.10 Importance of Diazonium Salts in Synthesis of Aromatic Compounds – “Aryl fluorides and iodides cannot be prepared by direct halogenation. The cyano group cannot be introduced by nucleophilic substitution of chlorine in chlorobenzene but cyanobenzene can be easily obtained from diazonium salt.”

6.5 Preparation of Haloarenes – “Aryl chlorides and bromides can be easily prepared by electrophilic substitution of arenes with chlorine and bromine respectively in the presence of Lewis acid catalysts like iron or iron(III) chloride.” … “Fluoro compounds are not prepared by this method due to high reactivity of fluorine.”

7.4.2 Preparation of Phenols – “Chlorobenzene is fused with NaOH at 623K and 320 atmospheric pressure. Phenol is obtained by acidification of sodium phenoxide so produced…”