MHTCET 17 Apr 2026 Shift 2 Paper

Concept:Homologous series differ by repeated $-\mathrm{CH}_{2}-$ units, so moving to lower homologues reduces the carbon chain by one carbon each time.Explanation:The given acid is $\mathrm{CH}_{3}\left(\mathrm{CH}_{2}\right)_{2}\mathrm{COOH}$, which contains 4 carbon atoms and is known as butanoic acid.Each lower homologue has one carbon atom less, i.e. one less $-\mathrm{CH}_{2}-$ group.First lower homologue: 3 carbon atoms, $\mathrm{CH}_{3}\mathrm{CH}_{2}\mathrm{COOH}$ — propanoic acid.Second lower homologue: 2 carbon atoms, $\mathrm{CH}_{3}\mathrm{COOH}$ — ethanoic acid.Therefore, the second lower homologue of butanoic acid is ethanoic acid.Answer:Option B: Ethanoic acid.