Four structures are given in options (a) to (d) . Examine them and select the aromatic structures.

Options

A.
B.
C.
D.

Explanation

To determine which of the given structures are aromatic, we need to follow a systematic approach based on the criteria for aromaticity. Here’s a step-by-step solution:

### Step 1: Understand the Criteria for Aromaticity
A compound is considered aromatic if it meets the following criteria:
1. It must be cyclic (ring structure).
2. It must be planar (all atoms in the ring must lie in the same plane).
3. It must have a continuous overlap of p-orbitals (conjugated π-bonds).
4. It must follow Huckel's rule, which states that there should be \(4n + 2\) π electrons, where \(n\) is a non-negative integer (0, 1, 2, ...).

### Step 2: Analyze Each Structure

#### Structure A:
- **Cyclic**: Yes, it is a ring.
- **Planar**: Yes, all carbon atoms are sp² hybridized, making them planar.
- **Conjugated π-bonds**: Yes, there are π-bonds that can delocalize.
- **Count π electrons**: There are 2 π electrons.
- Applying Huckel's rule: \(4n + 2 = 2\) (where \(n = 0\)).
- This satisfies Huckel's rule.

**Conclusion**: Structure A is aromatic.

#### Structure B:
- **Cyclic**: Yes, it is a ring.
- **Planar**: Yes, all carbon atoms are sp² hybridized.
- **Conjugated π-bonds**: Yes, there are π-bonds.
- **Count π electrons**: There are 8 π electrons.
- Applying Huckel's rule: \(4n + 2 = 8\) (no integer \(n\) satisfies this).

**Conclusion**: Structure B is not aromatic.

#### Structure C:
- **Cyclic**: Yes, it is a ring.
- **Planar**: Yes, all carbon atoms are sp² hybridized.
- **Conjugated π-bonds**: Yes, there are π-bonds.
- **Count π electrons**: There are 12 π electrons.
- Applying Huckel's rule: \(4n + 2 = 12\) (no integer \(n\) satisfies this).

However, if we consider the individual rings, one of the rings may still be aromatic.
- The first ring has 6 π electrons (satisfies Huckel's rule).

**Conclusion**: Structure C is aromatic because at least one of its rings is aromatic.

#### Structure D:
- **Cyclic**: Yes, it is a ring.
- **Planar**: Yes, all atoms are in the same plane.
- **Conjugated π-bonds**: Yes, there are π-bonds.
- **Count π electrons**: There are 4 π electrons.
- Applying Huckel's rule: \(4n + 2 = 4\) (no integer \(n\) satisfies this).

**Conclusion**: Structure D is not aromatic.

### Final Answer:
The aromatic structures are **A and C**.

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