CBSE Class 12 Chemistry — Aldehydes, Ketones and Carboxylic Acids

Give reasons for the following: (3 × 1) (a) Carboxylic acids have higher boiling point than alcohols of comparable molecular masses. (b) Alpha (α) hydrogens of aldehydes and ketones are acidic in nature. (c) Nucleophilic addition of ammonia and its derivatives does not occur with carbonyl group in strongly acidic medium.

(a) (i) An organic compound (X) has the molecular formula $C_5H_{10}O$. Draw structures for (X) if it: (3 + 2) (I) does not give Tollen's test but gives a positive iodoform test. (II) does not give Tollen's test and iodoform test but undergoes Aldol condensation. (III) undergoes Cannizzaro's reaction. (ii) Show how each of the following compounds can be converted to benzoic acid: (I) Acetophenone (II) Ethyl benzene OR (b) Answer the following questions: $(5 \times 1)$ (i) Draw structure of the 2, 4-dinitrophenyl hydrazone derivative of benzaldehyde. (ii) Arrange the following in increasing order of their reactivity towards HCN: Di-tert. butyl ketone, Acetaldehyde, Acetone (iii) Give a simple chemical test to distinguish between benzoic acid and ethyl benzoate. (iv) Write the name of the reagent to convert Ethanenitrile to Ethanal. (v) Draw the structure of 'X' in the following reaction: Cyclohexanol —($CrO_3$)→ 'X'