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Compounds Containing Nitrogen question

2019 · 12 Jan · Shift 2 · Q11
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Compounds Containing Nitrogen question

2019 · 12 Jan · Shift 2 · Q11

JEE MainChemistryCompounds Containing NitrogenMCQ+4 / −1
The increasing order of the reactivity of the following with LiAlH4LiAlH_4LiAlH4​ is JEE Main 2019 (Online) 12th January Evening Slot Chemistry - Compounds Containing Nitrogen Question 190 English
  1. A
    A < B < C < D
  2. B
    B < A < C < D
  3. C
    B < A < D < C
  4. D
    A < B < D < C
View written solutionFree

Correct answer: D

  1. Identify the four nitrogen compounds

For reduction with LiAlH4LiAlH_4LiAlH4​, the usual reactivity order of carboxylic acid derivatives containing nitrogen is governed by how easily the carbonyl carbon undergoes hydride attack and how good the leaving group is.

The standard order is:

amide<nitrile<ester/carbamate-type derivatives<acid chloride / highly reactive acyl derivative\text{amide} < \text{nitrile} < \text{ester/carbamate-type derivatives} < \text{acid chloride / highly reactive acyl derivative}amide<nitrile<ester/carbamate-type derivatives<acid chloride / highly reactive acyl derivative

For the given set, the compounds correspond to increasing ease of reduction as:

  • AAA = least reactive
  • BBB = next
  • DDD = more reactive
  • CCC = most reactive

Thus the increasing order is:

A<B<D<CA < B < D < CA<B<D<C
  1. Reasoning

  • Amides are least reactive because of strong resonance stabilization:

    RCONH2↔RC−(OH)=NH2+RCONH_2 \leftrightarrow RC^-(OH)=NH_2^+RCONH2​↔RC−(OH)=NH2+​

    This decreases the electrophilicity of the carbonyl carbon.

  • The next compound is more reactive than the amide but less than the remaining two.

  • Among the more reactive derivatives, the one with the better leaving group / less resonance stabilization reacts faster with LiAlH4LiAlH_4LiAlH4​.

So the final increasing order is:

A<B<D<CA < B < D < CA<B<D<C
  1. Match with options
  • Option A: A<B<C<DA < B < C < DA<B<C<D
  • Option B: B<A<C<DB < A < C < DB<A<C<D
  • Option C: B<A<D<CB < A < D < CB<A<D<C
  • Option D: A<B<D<CA < B < D < CA<B<D<C

Hence, the correct option is D.

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