Q25 / 170 · Manipal (MET) 2017 · Chemistry

Which of the following is most basic ?

  • Correct answer
    A
    $\mathrm{CH}_3 \mathrm{CH}_2 \mathrm{NH}_2$
  • B
    $\mathrm{CH}_3 \mathrm{CONH}_2$
  • C
    $\mathrm{C}_6 \mathrm{H}_5 \mathrm{CONCH}_3$
  • D
    $\mathrm{NH}_2 \mathrm{NH}_2$

Solution

Due to $-R$ effect of the $\mathrm{C}=\mathrm{O}$ group the electron density on the N -atom decreases, hence amides are weaker base than $\mathrm{NH}_3$ and aliphatic amines. Further due to $-I$ effect of $\mathrm{NH}_2$ group, the electron density on the other N -atom decreases. As a result, $\mathrm{NH}_2 \mathrm{NH}_2$ is a much weaker base than $\mathrm{NH}_3$ and aliphatic amines. Therefore, ethylamine is most basic among these.

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

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