Choose the strongest base among the following :

Options

A. `C_6H_5NH_2`
B. p - `NO_2C_6H_4NH_2`
C. p- `CNC_6H_4NH_2`
D. `C_6H_5CH_2NH_2`

Explanation

To determine the strongest base among the given compounds, we need to analyze the structures and the electronic effects that influence the availability of the lone pair of electrons on the nitrogen atom in the amine group (NH2).

### Step-by-Step Solution:

1. **Identify the Compounds**:
- Option A: Aniline (C6H5NH2)
- Option B: Para-Nitroaniline (C6H4(NO2)NH2)
- Option C: Para-Anisidine (C6H4(OCH3)NH2)
- Option D: Benzylamine (C6H5CH2NH2)

2. **Draw the Structures**:
- Aniline: A benzene ring with an NH2 group.
- Para-Nitroaniline: A benzene ring with an NH2 group and a nitro (NO2) group at the para position.
- Para-Anisidine: A benzene ring with an NH2 group and a methoxy (OCH3) group at the para position.
- Benzylamine: A benzene ring with a CH2 group attached to the NH2 group.

3. **Analyze Resonance Effects**:
- In Aniline, the lone pair on nitrogen can participate in resonance with the benzene ring, reducing its availability for donation.
- In Para-Nitroaniline, the nitro group is a strong electron-withdrawing group (due to -I and -R effects), which further decreases the electron density on the nitrogen, making it less basic.
- In Para-Anisidine, the methoxy group has a +R effect (donating electrons) but also a -I effect (withdrawing electrons). However, the +R effect is stronger, allowing for some availability of the lone pair on nitrogen, making it more basic than aniline.

4. **Evaluate Benzylamine**:
- In Benzylamine, the NH2 group is attached to a CH2 group, which is not in resonance with the benzene ring. Therefore, the lone pair on nitrogen is free and available for donation, making it the most basic among the four compounds.

5. **Conclusion**:
- Based on the analysis, Benzylamine (Option D) has the highest availability of the lone pair on nitrogen for donation, making it the strongest base among the given options.

### Final Answer:
The strongest base among the following is **Option D: Benzylamine (C6H5CH2NH2)**.