Which of the given statement is correct?

Options

A. Boiling point of cis-But-2-ene gt trans-But-2-ene
B. Boiling point of trans-But-2-ene gt cis-But-2-ene
C. Boiling point of cis-But-2-ene = trans-But-2-ene
D. Boiling point cannot be predicted

Answer

To determine which statement about the boiling points of cis-2-butene and trans-2-butene is correct, we can analyze the molecular structures and their properties.

### Step-by-Step Solution:

1. **Identify the Structures**:
- Draw the structures of cis-2-butene and trans-2-butene.
- **Cis-2-butene**: The two methyl (CH₃) groups are on the same side of the double bond.
- **Trans-2-butene**: The two methyl groups are on opposite sides of the double bond.

2. **Analyze Steric Repulsion**:
- In cis-2-butene, the bulky methyl groups are on the same side, which leads to steric repulsion between them. This repulsion can affect the stability and physical properties of the molecule.
- In trans-2-butene, the bulky groups are positioned on opposite sides, reducing steric hindrance.

3. **Consider Dipole Moments**:
- **Cis-2-butene** has a net dipole moment because the two methyl groups create a polar molecule. The dipole moment does not cancel out.
- **Trans-2-butene** has a net dipole moment of zero because the dipole moments of the two methyl groups cancel each other out, making it a nonpolar molecule.

4. **Relate Dipole Moment to Boiling Point**:
- Molecules with higher dipole moments tend to have higher boiling points due to stronger intermolecular forces (like dipole-dipole interactions).
- Since cis-2-butene is polar and has a significant dipole moment, it is expected to have a higher boiling point than trans-2-butene, which is nonpolar.

5. **Compare Boiling Points**:
- The boiling point of cis-2-butene is reported to be 276.7 K.
- The boiling point of trans-2-butene is reported to be 273.9 K.
- Therefore, cis-2-butene has a greater boiling point than trans-2-butene.

6. **Conclusion**:
- Based on the analysis, the correct statement is: **The boiling point of cis-2-butene is greater than that of trans-2-butene**.

### Final Answer:
The correct statement is (a): Boiling point of cis-2-butene is greater than that of trans-2-butene.