Which has zero dipole moment

Options

A. Cis-2-butene
B. Trans-2-butene
C. 1-butene
D. 2-methyl-1-propene

Explanation

To determine which compound has a zero dipole moment, we need to analyze the molecular structures of the given options: cis-2-butene, trans-2-butene, 1-butene, and 2-methyl-1-propene.

### Step-by-Step Solution:

1. **Understanding Dipole Moment**:
- A molecule has a dipole moment if there is an uneven distribution of electron density, leading to a positive and negative end (pole). If the dipole moments of the individual bonds in a molecule cancel each other out, the molecule will have a zero dipole moment.

2. **Analyzing Cis-2-butene**:
- Cis-2-butene has the structure where the two methyl groups (CH₃) are on the same side of the double bond. This creates a net dipole moment because the dipole moments of the C-H bonds do not cancel out completely. Therefore, cis-2-butene does not have a zero dipole moment.

3. **Analyzing Trans-2-butene**:
- Trans-2-butene has the structure where the two methyl groups are on opposite sides of the double bond. In this case, the dipole moments from the two methyl groups cancel each other out, resulting in a net dipole moment of zero. Thus, trans-2-butene has a zero dipole moment.

4. **Analyzing 1-butene**:
- 1-butene has a structure where the double bond is at the end of the carbon chain. The dipole moments from the C-H bonds do not cancel out due to the asymmetrical arrangement of the atoms, resulting in a non-zero dipole moment.

5. **Analyzing 2-methyl-1-propene**:
- 2-methyl-1-propene has a branched structure. The presence of the methyl group creates an asymmetrical distribution of electron density, leading to a non-zero dipole moment.

6. **Conclusion**:
- Among the given options, only trans-2-butene has a zero dipole moment.

### Final Answer:
**Option 2: Trans-2-butene has a zero dipole moment.**