To determine the basic strength of aniline derivatives, we consider the effect of substituents on the benzene ring. Nitro groups (-NO2) are electron-withdrawing groups, which decrease the electron density on the benzene ring, making the amino group less available for donation of a proton, hence decreasing its basicity. The position of the nitro group relative to the amino group also plays a significant role.
In general, the closer the electron-withdrawing group is to the amino group, the lower the basicity of the compound. So, the correct order of basic strength for the given anilines is:
(D) o-nitroaniline > m-nitroaniline > p-nitroaniline
Here's why:
o-nitroaniline has the nitro group at the ortho position relative to the amino group. This position is closest to the amino group, resulting in the most significant decrease in basicity.
m-nitroaniline has the nitro group at the meta position, which is not as close to the amino group as the ortho position, so it's less electron-withdrawing and hence less basic than o-nitroaniline.
p-nitroaniline has the nitro group at the para position, which is farthest from the amino group among the three positions. Hence, it has the least effect on the basicity of the amino group, making it the most basic among the three.
