pKb of aniline is lower than the m-nitroaniline.

Question 18:pKb of aniline is lower than the m-nitroaniline.

The correct answer is – The basicity of an amine is often measured by its pKb value, which is the negative logarithm of its base dissociation constant (Kb). A lower pKb value indicates stronger basicity, i.e., the ability of the amine to accept a proton (H+) and form a conjugate acid. In the case of aniline and m-nitroaniline, aniline has a lower pKb value than m-nitroaniline. This means that aniline is a stronger base than m-nitroaniline, i.e., it has a greater ability to accept a proton and form a conjugate acid. The reason for this is that the amino group (-NH2) in aniline is more available to accept a proton than the nitro group (-NO2) in m-nitroaniline due to the electron-donating nature of the amino group. The presence of the electron-withdrawing nitro group in m-nitroaniline reduces the basicity of the molecule, resulting in a higher pKb value compared to aniline.