Which of the following is the strongest base :-

Options

A. `C_(6)H_(5)NH_(2)`
B. `m-NO_(2)C_(6)H_(4)NH_(2)`
C. `p-NO_(2)C_(6)H_(4)NH_(2)`
D. `C_(6)H_(5)-CH_(2) - NH_(2)`

Answer

To determine which of the following compounds is the strongest base, we will analyze the basicity of each compound step by step.

### Step 1: Identify the Compounds
The compounds mentioned are:
1. Aniline (C6H5-NH2)
2. Meta Nitro Aniline (C6H4(NO2)-NH2)
3. Para Nitro Aniline (C6H4(NO2)-NH2)
4. Benzyl Amine (C6H5-CH2-NH2)

### Step 2: Analyze Aniline
- **Structure**: Aniline has a nitrogen atom attached to a benzene ring.
- **Effect of the Benzene Ring**: The benzene ring is an electron-withdrawing group due to resonance. The lone pair of electrons on nitrogen can participate in resonance with the benzene ring, making them less available for protonation.
- **Conclusion**: Aniline is a weak base due to the resonance effect.

### Step 3: Analyze Meta Nitro Aniline
- **Structure**: Meta Nitro Aniline has a nitro group (NO2) at the meta position relative to the amino group (NH2).
- **Effect of the Nitro Group**: The nitro group is an electron-withdrawing group through the -I (inductive) effect. However, since it is in the meta position, it does not significantly affect the resonance of the lone pair on nitrogen.
- **Conclusion**: Meta Nitro Aniline is less basic than Aniline because the nitro group still withdraws electron density from the nitrogen, but not as effectively as in the para position.

### Step 4: Analyze Para Nitro Aniline
- **Structure**: Para Nitro Aniline has the nitro group at the para position.
- **Effect of the Nitro Group**: The para nitro group exerts both -I and -R (resonance) effects. It pulls electron density away from the nitrogen atom, making the lone pair less available for donation.
- **Conclusion**: Para Nitro Aniline is less basic than both Aniline and Meta Nitro Aniline due to the strong electron-withdrawing effects of the nitro group.

### Step 5: Analyze Benzyl Amine
- **Structure**: Benzyl Amine has a nitrogen atom attached to a benzyl group (C6H5-CH2-).
- **Effect of the Methylene Group**: The methylene group (CH2) is an electron-donating group. It provides electron density to the nitrogen, making the lone pair more available for protonation.
- **Conclusion**: Benzyl Amine is the strongest base among the compounds listed because the electron-donating effect of the methylene group enhances the basicity of the amine.

### Final Conclusion
Based on the analysis:
- **Strongest Base**: Benzyl Amine
- **Weakest Base**: Para Nitro Aniline