Which of the following has maximum number of two-fold axis of symmetry.

Options

A. Ethylene
B. Cyclopropane
C. Cyclobutane
D. Benzene

Explanation

To determine which of the given compounds has the maximum number of two-fold axes of symmetry, we will analyze each compound step by step.

### Step 1: Understand Two-Fold Axis of Symmetry
A two-fold axis of symmetry is an imaginary line through a molecule such that if you rotate the molecule 180 degrees around this line, the molecule appears the same as it did before the rotation.

### Step 2: Analyze Benzene
- Benzene (C6H6) is a planar molecule with a hexagonal ring structure.
- It has two-fold axes of symmetry:
1. One axis passes through two opposite carbon atoms.
2. Another axis passes through the center of the ring and bisects the angle between two adjacent carbon atoms.
- Therefore, benzene has **2 two-fold axes of symmetry**.

### Step 3: Analyze Ethylene
- Ethylene (C2H4) is a planar molecule with a double bond between two carbon atoms.
- It has only **1 two-fold axis of symmetry**, which is the axis that passes through the two carbon atoms.

### Step 4: Analyze Cyclobutane
- Cyclobutane (C4H8) is a cyclic molecule with four carbon atoms.
- It has **1 two-fold axis of symmetry**, which goes through two opposite carbon atoms.

### Step 5: Analyze Cyclopropane
- Cyclopropane (C3H6) is a cyclic molecule with three carbon atoms.
- It also has **1 two-fold axis of symmetry**, which goes through one carbon atom and the midpoint of the opposite side.

### Step 6: Compare the Results
- Benzene: 2 two-fold axes of symmetry
- Ethylene: 1 two-fold axis of symmetry
- Cyclobutane: 1 two-fold axis of symmetry
- Cyclopropane: 1 two-fold axis of symmetry

### Conclusion
Benzene has the maximum number of two-fold axes of symmetry among the given options.

The correct answer is **Benzene**.

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