Ch 12 covers aldehydes (R-CHO), ketones (R-CO-R'), and carboxylic acids (R-COOH) — preparation, nucleophilic addition reactions, special reactions, and acidity comparisons.
The C=O group undergoes nucleophilic addition (HCN, NaHSO₃, Grignard, NH₃ derivatives). Aldehydes more reactive than ketones (less steric, more +ve carbon). Aldol condensation: α-H present + dilute NaOH. Cannizzaro: no α-H + conc. NaOH (disproportionation). Tollens: Ag⁺ → Ag mirror (aldehydes only). Fehling: Cu²⁺ → Cu₂O red ppt.
Preparation: oxidation of 1° alcohols/aldehydes, hydrolysis of nitriles, Grignard + CO₂. Acidity: stabilised by resonance of carboxylate ion (two equivalent C-O bonds). EWG increase acidity (ClCH₂COOH > CH₃COOH). Reactions: esterification (Fischer), acid chloride formation (SOCl₂), decarboxylation, HVZ reaction.
Download: https://ncert.nic.in/textbook/pdf/lech203.pdf | Part II: https://ncert.nic.in/textbook/pdf/lech2ps.zip
Tollens' reagent (ammoniacal silver nitrate, [Ag(NH₃)₂]⁺) is a mild oxidising agent. Aldehydes are easily oxidised to carboxylate ions, reducing Ag⁺ to metallic silver (silver mirror). Ketones cannot be oxidised under these mild conditions, so no reaction occurs. Hence only aldehydes give a positive silver mirror test.
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