Most basic compound amongst the given options: Benzylamine (option A)

Explanation:

Introduction:
In organic chemistry, basicity refers to the ability of a compound or molecule to accept a proton (H+) or donate a pair of electrons. The basicity of a compound depends on the availability of lone pairs of electrons on the atom or group of atoms.

Benzylamine (option A):
- Benzylamine is an organic compound with the formula C6H5CH2NH2.
- It consists of a benzene ring (C6H5) attached to an amino group (-NH2) through a methylene group (CH2).
- The lone pair of electrons on the nitrogen atom in the amino group can act as a Lewis base and readily accept a proton (H+).
- The lone pair of electrons is available for donation due to the electron-withdrawing nature of the benzene ring, which increases the basicity.

Aniline (option B):
- Aniline is an organic compound with the formula C6H5NH2.
- It consists of a benzene ring (C6H5) attached to an amino group (-NH2).
- The lone pair of electrons on the nitrogen atom in the amino group can also act as a Lewis base and accept a proton (H+).
- However, compared to benzylamine, aniline is less basic due to the electron-donating nature of the benzene ring. The lone pair of electrons is less available for donation.

Acetanilide (option C):
- Acetanilide is an organic compound with the formula C6H5NH(C2H3O).
- It consists of a benzene ring (C6H5) attached to an acetyl group (-C2H3O) through an amino group (-NH).
- The lone pair of electrons on the nitrogen atom in the amino group can also act as a Lewis base and accept a proton (H+).
- However, the presence of the acetyl group decreases the basicity compared to aniline. The electron-withdrawing nature of the acetyl group decreases the availability of the lone pair of electrons.

p-Nitroaniline (option D):
- p-Nitroaniline is an organic compound with the formula C6H6N2O2.
- It consists of a benzene ring (C6H6) attached to an amino group (-NH2) and a nitro group (-NO2) at the para position (opposite to the amino group).
- The lone pair of electrons on the nitrogen atom in the amino group can also act as a Lewis base and accept a proton (H+).
- However, the presence of the nitro group decreases the basicity compared to aniline. The electron-withdrawing nature of the nitro group decreases the availability of the lone pair of electrons.

Conclusion:
Amongst the given options, benzylamine (option A) is the most basic compound. The electron-withdrawing nature of the benzene ring increases the availability of the lone pair of electrons on the nitrogen atom, making benzylamine more basic compared to aniline, acetanilide, and p-nitroaniline.