Identify the correct statement

Options

A. cis-2-butene has zero dipole moment
B. cis-2-butene has higher melting point than trans counterpart
C. trans-2-pentene has zero dipole moment
D. trans isomers have higher melting point than cis

Answer

To identify the correct statement among the options provided, we will analyze each statement one by one.

### Step-by-Step Solution:

1. **Statement 1: "Cis-2-butene has zero dipole moment."**
- **Analysis:** The structure of cis-2-butene has both methyl groups (CH3) on the same side of the double bond. This results in a net dipole moment because the dipoles from the C-H bonds do not cancel out. Therefore, this statement is **incorrect**.

2. **Statement 2: "Cis-2-butene has a higher melting point than the trans counterpart."**
- **Analysis:** The cis isomer has a bent structure, which leads to poorer packing in the crystal lattice compared to the trans isomer, which has a more linear structure allowing for better packing. As a result, trans-2-butene has a higher melting point than cis-2-butene. Thus, this statement is **incorrect**.

3. **Statement 3: "Trans-2-pentene has zero dipole moment."**
- **Analysis:** In trans-2-pentene, the two different groups (methyl and ethyl) are on opposite sides of the double bond. The dipole moments from these groups do not cancel out completely because they are not equal in magnitude. Therefore, this statement is also **incorrect**.

4. **Statement 4: "Trans isomers have a higher melting point than cis."**
- **Analysis:** As previously discussed, trans isomers pack better in the solid state due to their linear structure, leading to a higher melting point compared to their cis counterparts. This statement is **correct**.

### Conclusion:
The correct statement is **Statement 4: "Trans isomers have a higher melting point than cis."**

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