See image — Aromatic Hydrocarbons Chemistry Question

💡 Solution & Explanation

Concept: The Reimer-Tiemann reaction is a named organic reaction in which phenol reacts with chloroform (CHCl3) in the presence of aqueous sodium hydroxide (NaOH) followed by acidic workup (H+) to introduce an aldehyde group (CHO) ortho to the hydroxyl group on the benzene ring, producing salicylaldehyde (2-hydroxybenzaldehyde) as the major product. Step-by-step reasoning: 1. The reactants are phenol and CHCl3 under NaOH/Heat conditions with H+ workup. 2. Under strongly basic conditions, CHCl3 loses a proton to form trichloromethyl carbanion (CCl3−), which further loses Cl− to generate dichlorocarbene (:CCl2), a highly reactive electrophilic intermediate. 3. Dichlorocarbene attacks the electron-rich aromatic ring of the phenoxide ion (formed from phenol + NaOH) preferentially at the ortho position. 4. The intermediate undergoes hydrolysis and tautomerization to give the sodium salt of salicylaldehyde, which upon acidification (H+) yields 2-hydroxybenzaldehyde (salicylaldehyde). 5. This sequence — phenol + CHCl3/NaOH/Heat → ortho-hydroxybenzaldehyde — is the defining transformation of the Reimer-Tiemann reaction. Why other options fail: - (a) Perkin reaction: involves condensation of an aromatic aldehyde with an acid anhydride in the presence of a base to form an α,β-unsaturated acid. No phenol or CHCl3 involved. - (b) Sandmeyer reaction: involves replacement of a diazonium group with CN, Cl, Br, etc., using copper salts. Completely unrelated. - (d) Cannizzaro reaction: involves disproportionation of aldehydes lacking α-hydrogens under strong base to give an alcohol and a carboxylic acid. No CHCl3 or phenol involved. Therefore, the correct answer is C.