The correct decreasing order of $\mathrm{p} K_b$ is

The correct decreasing order of $\mathrm{p} K_b$ is
  1. I $>$ II $>$ III $>$ IV
  2. III $>$ IV $>$ II $>$ I
  3. II $>$ III $>$ IV $>$ I
  4. IV $>$ II $>$ I $>$ III

Solution

Substituent with strong $+R$ effect, $+I$ effect and weaker $-I$ effect increases the basicity. Hence $\mathrm{p} K_b$ decreases. Also, alkylamines are stronger bases than arylamines. So, the order is (4).

Asked in: NEET 2008 (Screening)

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