Question

The correct increasing order of basic strength for the following compounds is ______.

• A. $II<III<I$
• B. $III<II<I$
• C. $III<I<II$
• D. $II<I<III$

Answer 1

The correct option is D $II<I<III$

Comparing the Basic strength
The electron donating group increases the basic strength of aniline and electron withdrawing group decreases the basic strength of aniline.


Increasing order of the basic strength of the compounds is:
$\left(ii\right)<\left(i\right)<\left(iii\right)$
Compound $\left(iii\right)$ will be most basic among these compounds due to the presence of the electron donating group (alkyl group) which increases the electron density on nitrogen atom. Moreover it shows hypercojugation effect as well which also increases electron density and hence basic strength.

Compound $\left(ii\right)$ will be least basic among these compounds due to the presence of electron withdrawing group $\left(N{O}_2\right)$. which decreases the electron density on nitrogen atom via mesomeric $(-M/-R)$ effect thus making it less available for protonation.
Hence, the correct answer is option $\left(D\right)$.