An example of a antiaromatic species is

Options

A.
B.
C.
D.

Answer

To determine an example of an antiaromatic species from the given options, we need to follow a systematic approach. Here’s a step-by-step solution:

### Step 1: Understand the Criteria for Antiaromaticity
Antiaromatic compounds must satisfy the following conditions:
1. The molecule must be **planar**.
2. The molecule must be **cyclic**.
3. There must be **conjugation** (the presence of overlapping p-orbitals).
4. The molecule must contain **4n pi electrons** (where n is a non-negative integer).

### Step 2: Analyze Each Option
Let’s evaluate each of the provided options based on the criteria for antiaromaticity.

#### Option 1:
- **Structure**: Contains a cyclic structure with conjugation.
- **Hybridization**: All carbon atoms are sp² hybridized, making it planar.
- **Pi Electrons**: It has 6 pi electrons (from 3 pi bonds and a lone pair).
- **Conclusion**: It follows Huckel's rule (4n + 2), so it is **aromatic**, not antiaromatic.

#### Option 2:
- **Structure**: Another cyclic structure with conjugation.
- **Hybridization**: All carbon atoms are sp² hybridized, making it planar.
- **Pi Electrons**: It has 6 pi electrons (from 3 pi bonds).
- **Conclusion**: It follows Huckel's rule (4n + 2), so it is **aromatic**, not antiaromatic.

#### Option 3:
- **Structure**: Contains two rings, cyclic and conjugated.
- **Hybridization**: All carbon atoms are sp² hybridized, making it planar.
- **Pi Electrons**: It has 10 pi electrons (from 5 pi bonds).
- **Conclusion**: It follows Huckel's rule (4n + 2), so it is **aromatic**, not antiaromatic.

#### Option 4:
- **Structure**: A cyclic structure with conjugation.
- **Hybridization**: All carbon atoms are sp² hybridized, making it planar.
- **Pi Electrons**: It has 4 pi electrons (from 2 pi bonds).
- **Conclusion**: It follows the 4n rule (where n=1), so it is **antiaromatic**.

### Step 3: Final Answer
Based on the analysis, the example of an antiaromatic species is **Option 4**.

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