JEE Main · 2026 · 28 Jan 2026 · Shift 2 · Aldehydes Ketones and Carboxylic Acids

Each route gives a carboxylic acid: route A gives benzoic acid (via the nitrile from the diazonium salt), route B gives propanoic acid (oxidation of propanal by Tollens' reagent), route C gives formic acid (methane to methanal, then dichromate oxidation), and route D gives phenylacetic acid (carbonation of the Grignard reagent). Formic acid, with no electron-donating group to destabilise its conjugate base, is the strongest; benzoic acid, whose ring withdraws by resonance directly from the carboxyl, is stronger than phenylacetic acid, whose $\mathrm{C}{\mathrm{H}}_2$ spacer insulates the ring; propanoic acid is the weakest. The decreasing order of acidic strength is formic acid $>$ benzoic acid $>$ phenylacetic acid $>$ propanoic acid, that is C $>$ A $>$ D $>$ B.