Match List-I with List-II.
| List-I (Reaction / test) | List-II (Reagents used) |
|---|---|
| (A) Kolbe’s reaction | (I) Concentrated HCl and ZnCl2 |
| (B) Reimer-Tiemann reaction | (II) CHCl3 and aqueous NaOH |
| (C) Williamson synthesis | (III) NaOH, then CO2 and H+ |
| (D) Lucas test | (IV) Alkyl halide and sodium alkoxide |
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → A-III, B-II, C-IV, D-I
Kolbe’s and Reimer-Tiemann reactions both start from phenol in the presence of NaOH, but they bring in different groups: CO2 gives –COOH, and CHCl3 gives –CHO at the ortho position.
(A) Kolbe’s reaction — This matches (III) NaOH, then CO2 and H+. NaOH turns phenol into the more reactive phenoxide ion, which undergoes substitution with carbon dioxide, a weak electrophile; acidification gives salicylic acid (2-hydroxybenzoic acid).
(B) Reimer-Tiemann reaction — This matches (II) CHCl3 and aqueous NaOH. Chloroform in the presence of sodium hydroxide puts a –CHO group at the ortho position, giving salicylaldehyde.
(C) Williamson synthesis — This matches (IV) Alkyl halide and sodium alkoxide. The alkoxide ion displaces the halide ion and an ether is formed: R–X + R′–O−Na+ → R–O–R′ + NaX.
(D) Lucas test — This matches (I) Concentrated HCl and ZnCl2. The three classes of alcohols react with this reagent at different rates, so the time taken for turbidity tells them apart.
NCERT (2026-27 edition):
7.4.4 Chemical Reactions – “2. Kolbe’s reaction”
“Phenoxide ion generated by treating phenol with sodium hydroxide is even more reactive than phenol towards electrophilic aromatic substitution. Hence, it undergoes electrophilic substitution with carbon dioxide, a weak electrophile. Ortho hydroxybenzoic acid is formed as the main reaction product.”
“3. Reimer-Tiemann reaction”
“On treating phenol with chloroform in the presence of sodium hydroxide, a –CHO group is introduced at ortho position of benzene ring. This reaction is known as Reimer - Tiemann reaction.”
“The difference in reactivity of three classes of alcohols with HCl distinguishes them from one another (Lucas test). Alcohols are soluble in Lucas reagent (conc. HCl and ZnCl2) while their halides are immiscible and produce turbidity in solution.”
7.6.1 Preparation of Ethers – “2. Williamson synthesis”
“It is an important laboratory method for the preparation of symmetrical and unsymmetrical ethers. In this method, an alkyl halide is allowed to react with sodium alkoxide.”