Table of contents

1. A Review of General Chemistry5h 5m
2. Molecular Representations1h 14m
3. Acids and Bases2h 46m
4. Alkanes and Cycloalkanes4h 17m
5. Chirality3h 39m
6. Thermodynamics and Kinetics1h 22m
7. Substitution Reactions1h 48m
8. Elimination Reactions2h 30m
9. Alkenes and Alkynes2h 9m
10. Addition Reactions3h 19m
11. Radical Reactions1h 58m
12. Alcohols, Ethers, Epoxides and Thiols2h 42m
13. Alcohols and Carbonyl Compounds2h 17m
14. Synthetic Techniques1h 26m
15. Analytical Techniques:IR, NMR, Mass Spect7h 3m
16. Conjugated Systems6h 13m
17. Ultraviolet Spectroscopy51m
18. Aromaticity2h 34m
19. Reactions of Aromatics: EAS and Beyond5h 1m
20. Phenols55m
21. Aldehydes and Ketones: Nucleophilic Addition4h 56m
22. Carboxylic Acid Derivatives: NAS2h 51m
23. The Chemistry of Thioesters, Phophate Ester and Phosphate Anhydrides1h 10m
24. Enolate Chemistry: Reactions at the Alpha-Carbon1h 53m
25. Condensation Chemistry2h 9m
26. Amines1h 43m
27. Heterocycles2h 0m
28. Carbohydrates5h 53m
29. Amino Acids4h 20m
30. Peptides and Proteins2h 42m
31. Catalysis in Organic Reactions1h 30m
32. Lipids 2h 50m
33. The Organic Chemistry of Metabolic Pathways2h 52m
34. Nucleic Acids1h 32m
35. Transition Metals6h 14m
36. Synthetic Polymers1h 49m

1. A Review of General Chemistry

Electronegativity

Organic Chemistry

1. A Review of General Chemistry

Electronegativity

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4:38 minutes

Problem 46g,h

Textbook Question

Which of the following molecules would you expect to have a dipole moment of zero?
g. BeCl₂
h. BF₃

Verified step by step guidance

Step 1: Understand the concept of dipole moment. A dipole moment arises when there is an uneven distribution of electron density in a molecule due to differences in electronegativity between atoms. For a molecule to have a dipole moment of zero, the individual bond dipoles must cancel each other out due to symmetry.

Step 2: Analyze the geometry of BeCl2. Beryllium chloride (BeCl2) has a linear molecular geometry because beryllium forms two bonds with chlorine atoms and has no lone pairs. The bond dipoles between Be and Cl point in opposite directions along the same axis, and due to the linear geometry, they cancel each other out, resulting in a dipole moment of zero.

Step 3: Analyze the geometry of BF3. Boron trifluoride (BF3) has a trigonal planar molecular geometry because boron forms three bonds with fluorine atoms and has no lone pairs. The bond dipoles between B and F are directed outward at 120° angles from each other. Due to the symmetrical trigonal planar geometry, the bond dipoles cancel each other out, resulting in a dipole moment of zero.

Step 4: Compare the symmetry of both molecules. Both BeCl2 and BF3 exhibit high symmetry in their molecular geometries, which is the key factor that leads to the cancellation of dipole moments.

Step 5: Conclude that both BeCl2 and BF3 have a dipole moment of zero due to their symmetrical molecular geometries, which cause the bond dipoles to cancel each other out.

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Key Concepts

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

Molecular Geometry

Molecular geometry refers to the three-dimensional arrangement of atoms within a molecule. The shape of a molecule is determined by the number of bonding pairs and lone pairs of electrons around the central atom. Understanding molecular geometry is crucial for predicting the polarity of a molecule, as symmetrical shapes often lead to nonpolar characteristics.

Dipole Moment

A dipole moment is a measure of the separation of positive and negative charges in a molecule, indicating its polarity. It arises when there is an uneven distribution of electron density, leading to partial positive and negative charges. Molecules with a dipole moment are polar, while those with a dipole moment of zero are nonpolar, often due to symmetrical arrangements of bonds.

Symmetry in Molecules

Symmetry in molecules plays a key role in determining their physical properties, including polarity. Molecules that exhibit high symmetry, such as linear or trigonal planar structures, can cancel out individual bond dipoles, resulting in a net dipole moment of zero. Recognizing the symmetry of a molecule helps predict whether it will be polar or nonpolar.

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