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Ch. 4 - Isomers: The Arrangement of Atoms in Space
Bruice - Organic Chemistry 8th Edition
Bruice8th EditionOrganic ChemistryISBN: 9780135213711Not the one you use?Change textbook
Chapter 5, Problem 6

Which of the following compounds have a dipole moment of zero?

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Step 1: Understand the concept of dipole moment. Dipole moment arises due to the difference in electronegativity between atoms in a molecule and the asymmetry in the molecular geometry. A molecule will have a dipole moment of zero if the individual bond dipoles cancel each other out due to symmetry.
Step 2: Analyze compound A. The molecule has two chlorine atoms and two hydrogen atoms symmetrically arranged around the double bond. The molecule is symmetrical, and the bond dipoles cancel each other out, resulting in a dipole moment of zero.
Step 3: Analyze compound B. The molecule has one chlorine atom and one hydrogen atom on each carbon of the double bond. The arrangement is not symmetrical, and the bond dipoles do not cancel each other out, resulting in a nonzero dipole moment.
Step 4: Analyze compound C. The molecule has two chlorine atoms on one carbon and two hydrogen atoms on the other carbon of the double bond. This arrangement is asymmetrical, and the bond dipoles do not cancel each other out, resulting in a nonzero dipole moment.
Step 5: Analyze compound D. The molecule has one chlorine atom and one hydrogen atom on each carbon of the double bond, but the arrangement is symmetrical. The bond dipoles cancel each other out, resulting in a dipole moment of zero.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Dipole Moment

A dipole moment is a measure of the separation of positive and negative charges in a molecule. It occurs when there is an uneven distribution of electron density, leading to a polar bond. The dipole moment is a vector quantity, having both magnitude and direction, and is crucial for understanding molecular polarity and interactions.
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Molecular Symmetry

Molecular symmetry refers to the balanced arrangement of atoms in a molecule. Symmetrical molecules, such as those with a uniform distribution of charge, often have a dipole moment of zero. Understanding symmetry helps predict the physical properties of molecules, including their polarity and reactivity.
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Polar vs. Nonpolar Molecules

Polar molecules have a significant dipole moment due to the presence of polar bonds and an asymmetrical shape, while nonpolar molecules have no net dipole moment. Nonpolar molecules can arise from symmetrical arrangements of identical atoms or from the cancellation of dipole moments in larger molecules, making it essential to analyze molecular structure to determine polarity.
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