Question

Which of the following has zero dipole moment?

• A. 1-Butene
• B. 2-Methyl- 1-propene
• C. cis-2-Butene
• D. trans-2-Butene

Hint:

It is visible that both the methyl groups are canceling each other out

Answer 1

The Correct Option is D

The question asks which compound among the given options has a zero dipole moment. Let us explore each option and understand the concepts of molecular symmetry and dipole moments to arrive at the correct answer.

Concept of Dipole Moment: A dipole moment is a measure of the separation of positive and negative charges in a molecule. It is a vector quantity, meaning that both magnitude and direction are important. If a molecule is symmetrical, the individual bond dipoles cancel each other out, resulting in a net dipole moment of zero.

Analysis of Each Compound:

1. 1-Butene: This molecule is not symmetrical due to the presence of a double bond between the first and second carbons. The asymmetry leads to a non-zero dipole moment.
2. 2-Methyl-1-propene: This molecule is also asymmetrical due to the branching caused by the methyl group and the position of the double bond. Thus, it has a non-zero dipole moment.
3. cis-2-Butene: In this molecule, similar groups are on the same side of the double bond. This creates a net dipole moment as the molecular symmetry is disrupted.
4. trans-2-Butene: The molecule is symmetrical as the similar groups are on opposite sides of the double bond. This symmetry causes the dipole moments to cancel each other out, resulting in a net dipole moment of zero.

Conclusion: Based on the analysis, trans-2-Butene is the compound with a zero dipole moment due to its symmetrical structure. The correct option is trans-2-Butene.