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

Resonance Structures

Organic Chemistry

1. A Review of General Chemistry

Resonance Structures

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4:33 minutes

Problem 7

Textbook Question

a. Predict the relative bond lengths of the three carbon–oxygen bonds in the carbonate ion.
b. What is the charge on each oxygen?

Verified step by step guidance

Step 1: Analyze the structure of the carbonate ion (CO₃²⁻). The carbonate ion consists of one carbon atom bonded to three oxygen atoms. It has a resonance structure, meaning the electrons are delocalized across the molecule.

Step 2: Predict the relative bond lengths. Due to resonance, the three carbon–oxygen bonds in the carbonate ion are equivalent. The delocalization of electrons results in bond lengths that are intermediate between a single bond and a double bond. Therefore, all three C–O bonds have the same length.

Step 3: Determine the charge distribution. The carbonate ion has a total charge of -2. This charge is distributed across the three oxygen atoms due to resonance. Each oxygen atom carries a partial negative charge.

Step 4: Use formal charge calculations to confirm the charge on each oxygen. The formal charge on each oxygen can be calculated using the formula: Formal charge = (Valence electrons) - (Non-bonding electrons) - (Bonding electrons/2). For the carbonate ion, each oxygen atom has a formal charge of -2/3 due to the resonance structure.

Step 5: Summarize the findings. The three carbon–oxygen bonds in the carbonate ion are of equal length due to resonance, and each oxygen atom carries a partial negative charge, contributing to the overall -2 charge of the ion.

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Key Concepts

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

Resonance Structures

Resonance structures are different ways of drawing the same molecule that illustrate the delocalization of electrons. In the case of the carbonate ion (CO3^2-), there are three resonance forms, each showing a different oxygen atom with a double bond to carbon. This delocalization leads to bond lengths that are intermediate between single and double bonds, affecting the overall stability and properties of the ion.

Bond Lengths

Bond length refers to the distance between the nuclei of two bonded atoms. In the carbonate ion, the bond lengths of the carbon-oxygen bonds are influenced by the resonance structures. The C=O bond (double bond) is shorter than the C-O bond (single bond), resulting in all three C-O bonds being of equal length due to resonance, which is typically shorter than a single bond but longer than a double bond.

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 non-bonding electrons, and half the number of bonding electrons. In the carbonate ion, each oxygen atom carries a formal charge of -2/3 due to the distribution of electrons across the resonance structures, which helps to stabilize the ion and explains the overall -2 charge of the carbonate ion.

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a. Predict the relative bond lengths of the three carbon–oxygen bonds in the carbonate ion. b. What is the charge on each oxygen?

Key Concepts

Resonance Structures

Bond Lengths

Formal Charge

Watch next

a. Predict the relative bond lengths of the three carbon–oxygen bonds in the carbonate ion.
b. What is the charge on each oxygen?