Q34 / 150 · MHT CET 2023 (13 May Shift 1) · Chemistry

Identify the CORRECT decreasing order of basic strength of compounds from following.

  • A
    $\mathrm{CH}_3 \mathrm{NH}_2>\left(\mathrm{CH}_3\right)_2 \mathrm{NH}>\mathrm{C}_6 \mathrm{H}_5 \mathrm{NH}_2>\mathrm{NH}_3$
  • Correct answer
    B
    $\left(\mathrm{CH}_3\right)_2 \mathrm{NH}>\mathrm{CH}_3 \mathrm{NH}_2>\mathrm{NH}_3>\mathrm{C}_6 \mathrm{H}_5 \mathrm{NH}_2$
  • C
    $\mathrm{NH}_3>\mathrm{CH}_3\mathrm{NH}_2>\left(\mathrm{CH}_3\right)_2 \mathrm{NH}>\mathrm{C}_6 \mathrm{H}_5 \mathrm{NH}_2$
  • D
    $\mathrm{C}_6 \mathrm{H}_5 \mathrm{NH}_2>\left(\mathrm{CH}_3\right)_2 \mathrm{NH}>\mathrm{CH}_3 \mathrm{NH}_2>\mathrm{NH}_3$

Solution

Arylamines in general are weaker bases than ammonia and aliphatic amines. Aliphatic amines are stronger bases' than ammonia. Among aliphatic amines, $2^{\circ}$ amine is a stronger base than $1^{\circ}$ amine. Hence, the correct decreasing order of basic strength is: $$ \left(\mathrm{CH}_3\right)_2 \mathrm{NH}>\mathrm{CH}_3 \mathrm{NH}_2>\mathrm{NH}_3>\mathrm{C}_6 \mathrm{H}_5 \mathrm{NH}_2 $$

Hence, the correct answer is option: 'B'.

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