Which one of the following is least basic in character?

Options

A.
B.
C.
D.

Answer

To determine which of the given compounds is least basic in character, we need to analyze the availability of the lone pair of electrons on the nitrogen atom in each compound. The basicity of a compound is influenced by how readily it can accept protons (H+ ions), which is largely dependent on the availability of lone pair electrons.

### Step-by-Step Solution:

1. **Identify the Compounds**: Let's denote the four options as A, B, C, and D. We need to evaluate the basicity of each based on the lone pair of nitrogen.

2. **Understand Basicity**: Basicity is defined by the ability of a compound to accept protons (H+). The more available the lone pair of electrons, the stronger the base.

3. **Analyze Option A**: In option A, the nitrogen lone pair is involved in aromaticity. This means that the lone pair is delocalized and not available for protonation. Therefore, option A is likely to be less basic.

4. **Analyze Option B**: In option B, there is resonance, but it is not aromatic. The lone pair is somewhat delocalized, which reduces its availability compared to a free lone pair, but it is still more available than in option A.

5. **Analyze Option C**: Option C also has resonance, which means the lone pair is partially delocalized. However, it may still be more available than in option A.

6. **Analyze Option D**: In option D, the lone pair on nitrogen is completely free and not involved in any resonance or aromaticity. This makes option D the most basic.

7. **Conclusion**: Since option A has the lone pair completely delocalized due to aromaticity, it is the least basic among the four options. Therefore, the answer is option A.

### Final Answer:
The least basic character is found in **Option A**.

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