Which of the following is the strongest base?

Options

A.
B.
C.
D.

Answer

To determine which of the given options is the strongest base, we will analyze each option based on the presence of electron-donating groups and their effects on the basicity of the compounds.

### Step-by-Step Solution:

1. **Identify the Compounds**: We have four options, each representing a different compound. We need to analyze the structure and substituents of each compound to determine their basicity.

2. **Analyze Option 1**:
- This compound is a 1,5-di-substituted aniline with two methyl groups attached to the ortho positions of the benzene ring.
- Methyl groups are electron-donating through the +I effect, which increases the electron density on the benzene ring and enhances the basicity of aniline.
- Therefore, this compound has increased basicity due to the presence of two methyl groups.

3. **Analyze Option 2**:
- This compound also has a nitrogen atom with a lone pair and two substituents: a methyl group and another group (assumed to be electron-withdrawing).
- The lone pair on nitrogen can participate in resonance with the benzene ring, but the presence of the electron-withdrawing group can decrease the overall electron density on the nitrogen.
- Thus, while this compound is basic, it is less basic than Option 1 due to the electron-withdrawing effect.

4. **Analyze Option 3**:
- This compound has two methyl groups on the nitrogen and is also ortho to the benzene ring.
- The presence of two electron-donating groups (methyl) increases the electron density on the nitrogen significantly.
- This compound has the highest electron density on the nitrogen due to both resonance and the +I effect from the methyl groups, making it the strongest base among the options.

5. **Analyze Option 4**:
- This is a simple aniline without any substituents.
- While aniline is basic, it lacks any electron-donating groups to enhance its basicity further.
- Therefore, this compound is the least basic among the four options.

6. **Conclusion**:
- After analyzing all four options, we conclude that Option 3, with the highest electron density due to the presence of two methyl groups, is the strongest base.

### Final Answer:
**Option 3 is the strongest base.**

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