Which of the following meet the requirements of the Huckel rule for aromatic compound

Options

A. Naphthalene
B. Cyclohexane
C. 1, 3, 5, 7 - Cyclooctatetraene
D. 1, 3 - Cyclobutadiene

Explanation

To determine which of the given compounds meets the requirements of Huckel's rule for aromatic compounds, we need to follow a systematic approach based on the criteria for aromaticity. Let's break it down step by step.

### Step 1: Understand Huckel's Rule
Huckel's rule states that for a compound to be aromatic, it must satisfy two main conditions:
1. The compound must be cyclic and planar.
2. The compound must have a conjugated π-electron system with a total number of π-electrons equal to \(4n + 2\), where \(n\) is a non-negative integer (0, 1, 2, ...).

### Step 2: Analyze Each Compound
Let’s analyze the options provided in the question.

**Option A: Naphthalene**
- Structure: Naphthalene consists of two fused benzene rings.
- Hybridization: All carbon atoms in naphthalene are sp² hybridized, which means they are in the same plane.
- π-electrons: Naphthalene has 5 π bonds, contributing 10 π-electrons (5 π bonds × 2 electrons per bond).
- Check Huckel's Rule: \(n = 2\) gives \(4(2) + 2 = 10\). Thus, naphthalene is aromatic.

**Option B: Cyclohexane**
- Structure: Cyclohexane is a saturated cyclic compound.
- Hybridization: All carbon atoms are sp³ hybridized, meaning they are not planar.
- Conclusion: Cyclohexane does not meet the criteria for aromaticity.

**Option C: Cyclotetraene**
- Structure: Cyclotetraene has alternating double bonds.
- Hybridization: The hybridization of the carbon atoms is sp², but the compound is not planar due to its puckered conformation.
- π-electrons: Cyclotetraene has 4 π bonds, contributing 8 π-electrons.
- Check Huckel's Rule: \(n = 1\) gives \(4(1) + 2 = 6\). Since it has 8 π-electrons, it is anti-aromatic.

**Option D: 1,3-Cyclobutadiene**
- Structure: Cyclobutadiene has two double bonds.
- Hybridization: All carbon atoms are sp² hybridized, so they are in the same plane.
- π-electrons: It has 4 π-electrons (2 double bonds).
- Check Huckel's Rule: \(n = 0\) gives \(4(0) + 2 = 2\). Since it has 4 π-electrons, it is anti-aromatic.

### Step 3: Conclusion
Based on the analysis, the only compound that meets the requirements of Huckel's rule for aromatic compounds is **Option A: Naphthalene**.