Question

Consider the following four compounds I, II, III, and IV.


Choose the correct statement(s).

• A. The order of basicity is $II>I>III>IV$
• B. The magnitude of $p{K}_b$ difference between $I$ and $II$ is more than that between $III$ and $IV$
• C. Resonance effect is more in $III$ than in $IV$
• D. Steric effect makes compound $IV$ more basic than $III$

Answer 1

Answer: (C), (D)

Steric effect makes compound $IV$ more basic than $III$

a) Correct basic strength order of given compound is:
$\left(IV\right)>\left(II\right)>\left(I\right)>\left(III\right)$

c) In compound $IV$ due to SIR (steric inhibition due to resonance), $-N(C{H}_3{)}_2$ group becomes out of plane of the ring. It restricts delocalisation of lone pair of $N$ in the ring and make the compound more basic.