Which of the following is most basic?

Options

A.
B.
C.
D.

Answer

To determine which of the given compounds is the most basic, we need to analyze the basicity of each compound based on the substituents attached to the aniline structure. The basicity of an amine is influenced by the electron-donating or electron-withdrawing nature of the substituents.

### Step-by-Step Solution:

1. **Identify the Compounds**: The compounds given are:
- Methoxyaniline (OCH3-NH2)
- Nitroaniline (NO2-NH2)
- Chloroaniline (Cl-NH2)
- Aniline (NH2)

2. **Understand Basicity**: Basicity is the ability of a compound to donate a lone pair of electrons. Electron-donating groups increase basicity, while electron-withdrawing groups decrease basicity.

3. **Analyze Methoxyaniline**:
- The methoxy group (OCH3) is an electron-donating group due to resonance (+R effect).
- This increases the electron density on the nitrogen atom, enhancing its ability to donate electrons.
- Therefore, methoxyaniline is expected to be the most basic among the options.

4. **Analyze Nitroaniline**:
- The nitro group (NO2) is an electron-withdrawing group (-I effect).
- It decreases the electron density on the nitrogen atom, making it less basic.
- Thus, nitroaniline has the lowest basicity.

5. **Analyze Chloroaniline**:
- The chloro group (Cl) is also an electron-withdrawing group, but it has a weaker -I effect compared to the nitro group.
- Chlorine does not effectively donate electrons through resonance, so chloroaniline is less basic than aniline but more basic than nitroaniline.

6. **Analyze Aniline**:
- Aniline has no substituents that significantly affect its basicity.
- It has a moderate basicity, higher than nitroaniline and chloroaniline but lower than methoxyaniline.

7. **Conclusion**:
- The order of basicity from highest to lowest is:
1. Methoxyaniline (most basic)
2. Aniline
3. Chloroaniline
4. Nitroaniline (least basic)

### Final Answer:
**Methoxyaniline is the most basic among the given options.**