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Compounds Containing Nitrogen question

2021 · 16 Mar · Shift 2 · Q7
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Compounds Containing Nitrogen question

2021 · 16 Mar · Shift 2 · Q7

JEE MainChemistryCompounds Containing NitrogenMCQ+4 / −1
Ammonolysis of Alkyl halides followed by the treatment with NaOH solution can be used to prepare primary, secondary and tertiary amines. The purpose of NaOH in the reaction is :
  1. A
    to remove acidic impurities
  2. B
    to remove basic impurities
  3. C
    to activate NH3NH_3NH3​ used in the reaction
  4. D
    to increase the reactivity of alkyl halide
View written solutionFree

Correct answer: A

  1. Ammonolysis of alkyl halides

    Alkyl halides react with ammonia to give amines. For example: R−X+NH3→R−NH2+HXR-X + NH_3 \rightarrow R-NH_2 + HXR−X+NH3​→R−NH2​+HX

    The hydrogen halide formed does not remain free for long; it reacts with excess ammonia: NH3+HX→NH4XNH_3 + HX \rightarrow NH_4XNH3​+HX→NH4​X

    So, after the reaction, the reaction mixture contains ammonium salt such as NH4ClNH_4ClNH4​Cl, NH4BrNH_4BrNH4​Br, etc.

  2. Why is NaOH treatment needed?

    On treating the reaction mixture with aqueous NaOH, the ammonium salt is decomposed: NH4X+NaOH→NH3+NaX+H2ONH_4X + NaOH \rightarrow NH_3 + NaX + H_2ONH4​X+NaOH→NH3​+NaX+H2​O

    Also, any amine hydrochloride-like salts are converted into free amines by NaOH.

  3. Main purpose of NaOH

    The ammonium salts and related salts formed are acidic in nature (they arise due to neutralization by HXHXHX). NaOH, being a strong base, neutralizes/removes these acidic species and liberates the free amine.

  4. Check each option

    • A: to remove acidic impurities
      Correct. NaOH neutralizes acidic salts/impurities formed during the reaction.

    • B: to remove basic impurities
      Incorrect. NaOH is itself a base; it does not remove basic impurities.

    • C: to activate NH3NH_3NH3​ used in the reaction
      Incorrect. NaOH is added after ammonolysis, not for activating ammonia.

    • D: to increase the reactivity of alkyl halide
      Incorrect. NaOH is not used for this purpose here.

  5. Conclusion

    Therefore, the purpose of NaOH is: to remove acidic impurities\boxed{\text{to remove acidic impurities}}to remove acidic impurities​

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