JEE Advanced 2022 Paper 1 · Q18 · GOC: Inductive & Resonance Effects
Match the compounds in LIST-I with the observations in LIST-II, and choose the correct option.
LIST-I: (I) Aniline (II) o-Cresol (III) Cysteine (IV) Caprolactam
LIST-II: (P) Sodium fusion extract of the compound on boiling with FeSO$_4$, followed by acidification with conc. H$_2$SO$_4$, gives Prussian blue color. (Q) Sodium fusion extract of the compound on treatment with sodium nitroprusside gives blood red color. (R) Addition of the compound to a saturated solution of NaHCO$_3$ results in effervescence. (S) The compound reacts with bromine water to give a white precipitate. (T) Treating the compound with neutral FeCl$_3$ solution produces violet color.
Reveal answer + step-by-step solution
Correct answer:D
Solution
Apply functional-group qualitative tests to each compound.
(I) Aniline (C$_6$H$_5$NH$_2$) contains C and N (no S). Lassaigne's sodium fusion gives NaCN; boiling with FeSO$_4$ then acidifying with conc. H$_2$SO$_4$ produces Prussian blue (Fe$_4$[Fe(CN)$_6$]$_3$): TEST P is positive. Aniline also undergoes facile electrophilic bromination — Br$_2$/H$_2$O immediately yields 2,4,6-tribromoaniline (a white precipitate): TEST S is positive. Aniline does NOT contain S (no Q), does NOT have -COOH (no R), and -NH$_2$ does not give the violet FeCl$_3$ colour reserved for phenols (no T). Match: P, S.
(II) o-Cresol (2-methylphenol) — phenols give a characteristic violet/blue colour with neutral FeCl$_3$: TEST T is positive. o-Cresol is not strongly acidic enough to liberate CO$_2$ from NaHCO$_3$ (phenols typically do not — only the more acidic 2,4,6-trinitrophenol does). It does not contain N or S (no P, Q). Br$_2$/H$_2$O on phenol gives 2,4,6-tribromophenol white precipitate, but for o-cresol the methyl substituent reduces the reactivity at one ortho position — FIITJEE does NOT mark S for o-cresol. Match: T.
(III) Cysteine (HS-CH$_2$-CH(NH$_2$)-COOH) contains C, N, S, a … [truncated]
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