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 pK_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

pK_b different between I and II is 0.53 and that of III and IV is 4.6. 

So option (B) is incorrect 

Correct Statement (C), (D) 

The most basic compound in the given option is (II) and least basic compound is (III)

In 2,4,6-trinitro aniline (III) due to strong –R effect of –NO₂ groups, the \(\ell\).p. of –NH₂ is more involved with benzene ring hence it has least basic strength. 

Whereas (IV) N,N-Dimethyl 2,4,6-trinitro aniline, due to steric inhibition to resonance (SIR) effect; the lone pair of nitrogen is not in the plane of benzene, hence make it (\(\ell\).p.) more free to protonate