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Ch.1 - Structure and Bonding
Wade - Organic Chemistry 9th Edition
Wade9th EditionOrganic ChemistryISBN: 9780135213728Not the one you use?Change textbook
Chapter 1, Problem 39a-e

1. From what you remember of electronegativities, show the direction of the dipole moments of the following bonds.
2. In each case, predict whether the dipole moment is relatively large (electronegativity difference >0.5) or small.
a. C—Cl
b. C—H
c. C—Li
d. C—N
e. C—O

Verified step by step guidance
1
Step 1: Understand the concept of electronegativity. Electronegativity is a measure of an atom's ability to attract and hold onto electrons. In a bond, the atom with higher electronegativity will attract the shared electrons more strongly, creating a dipole moment.
Step 2: Determine the electronegativity values for the elements involved in each bond. For example, typical values are: Carbon (C) = 2.55, Chlorine (Cl) = 3.16, Hydrogen (H) = 2.20, Lithium (Li) = 0.98, Nitrogen (N) = 3.04, Oxygen (O) = 3.44.
Step 3: Calculate the electronegativity difference for each bond. Use the formula: |EA-EB|, where EA and EB are the electronegativities of atoms A and B respectively.
Step 4: Predict the direction of the dipole moment for each bond. The dipole moment points from the less electronegative atom to the more electronegative atom. For example, in the C—Cl bond, the dipole moment points towards Cl because Cl is more electronegative than C.
Step 5: Assess the magnitude of the dipole moment based on the electronegativity difference. If the difference is greater than 0.5, the dipole moment is relatively large; if less, it is relatively small. Apply this criterion to each bond to determine the relative size of the dipole moment.

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Key Concepts

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

Electronegativity

Electronegativity is a measure of an atom's ability to attract and hold onto electrons within a chemical bond. It varies across the periodic table, generally increasing from left to right and decreasing down a group. Understanding electronegativity differences between bonded atoms helps predict the direction and magnitude of dipole moments in molecules.
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Dipole Moment

A dipole moment arises in a molecule when there is a separation of charge due to differences in electronegativity between bonded atoms. It is a vector quantity, with both magnitude and direction, pointing from the less electronegative atom to the more electronegative atom. The size of the dipole moment is influenced by the electronegativity difference and the distance between the atoms.
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How dipole-dipole forces work.

Electronegativity Difference

The electronegativity difference between two bonded atoms determines the polarity of the bond. A difference greater than 0.5 typically indicates a polar bond with a significant dipole moment, while a smaller difference suggests a less polar bond. This concept is crucial for predicting whether a bond will have a large or small dipole moment, as seen in the examples provided.
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