JEE Main 2021 · 26 February · evening · Single correct · +4 / −1

Ceric ammonium nitrate and CHCl₃/alc. KOH are used for the identification of functional groups present in __________ and _______ respectively.

  1. (a) amine, alcohol
  2. (b) alcohol, phenol
  3. (c) alcohol, amine
  4. (d) amine, phenol
Answer and solution

Answer (c) alcohol, amine

Solution

Chemistry ma’am · 3 steps

Match each reagent to its colour or smell test: CAN turns red with alcohols, carbylamine smells of amines.

  1. Ceric ammonium nitrate. Yellow ceric ammonium nitrate solution turns red with an alcohol. The -OH group replaces a nitrate ligand on cerium and forms a red alkoxy cerium complex: (NH₄)₂[Ce(NO₃)₆] + ROH → (NH₄)₂[Ce(OR)(NO₃)₅] + HNO₃.
  2. Chloroform and alc. KOH. Warming chloroform and alcoholic KOH with a primary amine gives an isocyanide, which has a strong, very unpleasant smell. This is the carbylamine test.

    RNH₂ + CHCl₃ + 3KOH →(Δ) RNC + 3KCl + 3H₂O

  3. So. Ceric ammonium nitrate detects the alcohol group and CHCl₃/alc. KOH detects the amine group, in that order. That is option (c).

The idea to keep. Learn each test as reagent, group and sign together: CAN gives red with -OH of alcohols, and CHCl₃ with alc. KOH gives a foul-smelling isocyanide only with primary amines.

Answer from the NTA final answer key. Solution by PrepWiser.

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Asked about 40 times in JEE Main since 2020. This question is from 2021.