Which of the following molecules has the highest value of carbon-carbon bond energy?

Options

A. `C_2H_4`
B. `C_3H_8`
C. `C_2H_2`
D. `C_2H_6`

Explanation

To determine which of the given molecules has the highest carbon-carbon bond energy, we need to analyze the bond order of each molecule. The bond energy is directly related to the bond order; the higher the bond order, the greater the bond energy.

### Step-by-Step Solution:

1. **Identify the Molecules**: The molecules provided are:
- C2H4 (Ethylene)
- C3H8 (Propane)
- C2H2 (Acetylene)
- C2H6 (Ethane)

2. **Determine the Structure and Bond Order**:
- **C2H4 (Ethylene)**:
- Structure: H2C=CH2 (double bond between the two carbon atoms)
- Bond Order: 2 (one double bond)

- **C3H8 (Propane)**:
- Structure: CH3-CH2-CH3 (single bonds between carbon atoms)
- Bond Order: 1 (single bonds)

- **C2H2 (Acetylene)**:
- Structure: HC≡CH (triple bond between the two carbon atoms)
- Bond Order: 3 (one triple bond)

- **C2H6 (Ethane)**:
- Structure: H3C-CH3 (single bond between the two carbon atoms)
- Bond Order: 1 (single bond)

3. **Compare the Bond Orders**:
- C2H4: Bond Order = 2
- C3H8: Bond Order = 1
- C2H2: Bond Order = 3
- C2H6: Bond Order = 1

4. **Identify the Highest Bond Order**:
- The highest bond order is found in C2H2 (Acetylene) with a bond order of 3.

5. **Conclusion**:
- Therefore, the molecule with the highest carbon-carbon bond energy is C2H2 (Acetylene).

### Final Answer:
The molecule with the highest value of carbon-carbon bond energy is **C2H2 (Acetylene)**.