Can the amino group, in the aniline molecule, become meta-directing in an elecrophilic substitution reaction?

Options

A. No, it never shows meta directing properties.
B. Yes in a strongly acidic medium.
C. Yes, in a strongly alkaline medium.
D. Yes, in a non-polar solvent.

Answer

To determine whether the amino group in an aniline molecule can become meta-directing in an electrophilic substitution reaction, we will analyze the behavior of the amino group under different conditions.

### Step-by-Step Solution:

1. **Understand the Structure of Aniline:**
- Aniline consists of a benzene ring attached to an amino group (-NH2).
- The structure can be represented as:
```
NH2
|
C6H5
```

2. **Identify the Nature of the Amino Group:**
- The amino group is an electron-donating group due to the presence of a lone pair of electrons on the nitrogen atom.
- This group can donate its lone pair to the benzene ring, increasing the electron density.

3. **Resonance Structures:**
- The resonance effect of the amino group can be illustrated by drawing resonance structures. The lone pair on nitrogen can delocalize into the benzene ring, leading to increased electron density at the ortho and para positions.
- This means that the amino group activates the benzene ring towards electrophilic substitution, making it ortho- and para-directing.

4. **Effect of Acidic Medium:**
- In an acidic medium, the amino group can become protonated to form -NH3+. This protonation leads to a decrease in electron density on the benzene ring due to the -NH3+ acting as an electron-withdrawing group.
- In this case, the electron density is highest at the meta position, making the meta position more favorable for electrophilic attack.

5. **Effect of Alkaline Medium:**
- In a strongly alkaline medium, the amino group remains unprotonated and continues to donate electrons, maintaining its ortho- and para-directing properties.
- Thus, in alkaline conditions, the amino group does not show meta-directing behavior.

6. **Effect of Nonpolar Solvent:**
- In a nonpolar solvent, the polar nature of the aniline molecule (due to the amino group) will not facilitate a reaction. Therefore, no electrophilic substitution will occur in a nonpolar solvent.

### Conclusion:
- The amino group in aniline is primarily ortho- and para-directing due to its electron-donating resonance effect. However, in a strongly acidic medium, it can exhibit meta-directing properties due to the formation of a protonated species that withdraws electron density from the benzene ring.

### Final Answer:
- The amino group in aniline can become meta-directing in a strongly acidic medium.