Amongst the following the most basic compound is

Options

A.
B.
C.
D.

Answer

To determine the most basic compound among the given options (aniline, para amino aniline, para nitro aniline, and para amino benzaldehyde), we can analyze the effects of substituents on the basicity of the aniline structure.

### Step-by-Step Solution:

1. **Identify the Compounds**:
- Aniline (C6H5NH2)
- Para amino aniline (C6H4(NH2)2)
- Para nitro aniline (C6H4(NH2)(NO2))
- Para amino benzaldehyde (C6H4(NH2)(CHO))

2. **Understand Basicity**:
Basicity is the ability of a compound to donate a pair of electrons. In the context of amines, the presence of electron-donating or electron-withdrawing groups can significantly affect this ability.

3. **Analyze Each Compound**:
- **Aniline**: The amino group (-NH2) is an electron-donating group, which increases the electron density on the nitrogen, making it more basic.
- **Para Amino Aniline**: This compound has two amino groups. The presence of an additional amino group further increases the electron density, enhancing its basicity.
- **Para Nitro Aniline**: The nitro group (-NO2) is a strong electron-withdrawing group. This decreases the electron density on the nitrogen of the amino group, making it less basic.
- **Para Amino Benzaldehyde**: The aldehyde group (-CHO) is also electron-withdrawing, which reduces the basicity compared to aniline.

4. **Compare Basicities**:
- Aniline has moderate basicity due to one electron-donating group.
- Para amino aniline has the highest basicity due to two electron-donating amino groups.
- Para nitro aniline has the lowest basicity due to the strong electron-withdrawing nitro group.
- Para amino benzaldehyde has reduced basicity due to the electron-withdrawing aldehyde group.

5. **Conclusion**:
Among the four compounds, **para amino aniline** is the most basic compound due to the presence of two amino groups that significantly increase the electron density on the nitrogen atom.

### Final Answer:
The most basic compound is **para amino aniline**.