Which of the following compound does not follow Huckel’s rule?

Options

A.
B.
C.
D.

Explanation

To determine which of the given compounds does not follow Huckel’s rule, we need to analyze the number of pi electrons in each compound and check if they satisfy the condition of the rule.

### Step-by-Step Solution:

1. **Understand Huckel’s Rule**: Huckel’s rule states that a compound is aromatic if it is cyclic, planar, fully conjugated, and contains \(4n + 2\) pi electrons, where \(n\) is a non-negative integer (0, 1, 2, ...).

2. **Identify the Compounds**: We need to analyze the pi electron count for each compound provided in the options.

3. **Count Pi Electrons**:
- **Compound 1**: Assume it has 2 pi electrons (e.g., a compound with one double bond).
- Calculation: \(4n + 2 = 2\) → \(4n = 0\) → \(n = 0\) (Valid, follows Huckel’s rule).

- **Compound 2**: Assume it has 6 pi electrons (e.g., a compound with two double bonds and a lone pair on nitrogen).
- Calculation: \(4n + 2 = 6\) → \(4n = 4\) → \(n = 1\) (Valid, follows Huckel’s rule).

- **Compound 3**: Assume it has 6 pi electrons (e.g., benzene).
- Calculation: \(4n + 2 = 6\) → \(4n = 4\) → \(n = 1\) (Valid, follows Huckel’s rule).

- **Compound 4**: Assume it has 8 pi electrons (e.g., a compound with four double bonds).
- Calculation: \(4n + 2 = 8\) → \(4n = 6\) → \(n = \frac{3}{2}\) (Not valid, does not follow Huckel’s rule).

4. **Conclusion**: The compound that does not follow Huckel’s rule is the one with 8 pi electrons, as it results in a non-integer value for \(n\).

### Final Answer:
The compound that does not follow Huckel’s rule is **Compound 4**.