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

Formal Charges

Organic Chemistry

1. A Review of General Chemistry

Formal Charges

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5:26 minutes

Problem 16c,d

Textbook Question

Give each atom the appropriate formal charge:
c.
d.

Verified step by step guidance

Step 1: Recall the formula for calculating formal charge: Formal charge = (Valence electrons) - (Non-bonding electrons) - (1/2 × Bonding electrons). This formula will be applied to each atom in the given structures.

Step 2: For the first structure (tetramethylammonium ion), focus on the nitrogen atom. Nitrogen typically has 5 valence electrons. In this structure, nitrogen is bonded to four methyl groups, forming four single bonds. Since nitrogen has no lone pairs and is sharing 8 bonding electrons, calculate its formal charge using the formula.

Step 3: For the first structure, examine the carbon atoms in the methyl groups. Carbon typically has 4 valence electrons. Each carbon is bonded to three hydrogens and one nitrogen, forming four single bonds. Since there are no lone pairs on these carbons, calculate their formal charges.

Step 4: For the second structure (ammonia-borane complex), focus on the nitrogen atom. Nitrogen has 5 valence electrons. In this structure, nitrogen is bonded to three hydrogens and one boron atom. Nitrogen also has a lone pair of electrons. Use the formal charge formula to determine its charge.

Step 5: For the second structure, examine the boron atom. Boron typically has 3 valence electrons. In this structure, boron is bonded to three hydrogens and one nitrogen atom. Boron has no lone pairs, and it is sharing 8 bonding electrons. Use the formal charge formula to determine its charge.

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Key Concepts

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

Formal Charge

Formal charge is a theoretical charge assigned to an atom in a molecule, calculated based on the number of valence electrons, the number of bonds, and the number of non-bonding electrons. It helps in determining the most stable structure of a molecule by indicating how electrons are distributed among atoms. The formula for calculating formal charge is: Formal Charge = Valence Electrons - (Non-bonding Electrons + 1/2 Bonding Electrons).

Lewis Structures

Lewis structures are diagrams that represent the bonding between atoms in a molecule and the lone pairs of electrons that may exist. They provide a visual representation of the molecule's structure, allowing for the identification of formal charges and the overall electron distribution. Understanding how to draw and interpret Lewis structures is essential for predicting molecular geometry and reactivity.

Hybridization

Hybridization is the concept of mixing atomic orbitals to form new hybrid orbitals that can accommodate the bonding requirements of a molecule. In the case of nitrogen in the given structure, it typically undergoes sp³ hybridization, resulting in four equivalent hybrid orbitals that form sigma bonds with surrounding atoms. Recognizing hybridization is crucial for understanding molecular shape and bond angles.

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Textbook Question

Looking ahead in Chapter 3, we describe how the formal charge on an atom can be used to predict the number of lone pairs. Given the charge, or lack of charge, on each atom, fill in the electron pairs.

(a)