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

13. Alcohols and Carbonyl Compounds

Oxidizing and Reducing Agents

Organic Chemistry

13. Alcohols and Carbonyl Compounds

Oxidizing and Reducing Agents

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Problem 5c

Textbook Question

Calculate the oxidation numbers for the indicated atoms.
(c)

Verified step by step guidance

Identify the structure: The compound shown is a Grignard reagent, specifically phenylmagnesium bromide, where the phenyl group (C6H5) is bonded to a magnesium bromide (MgBr). The arrow points to the carbon atom in the phenyl group that is directly bonded to the magnesium.

Understand the Grignard reagent: In Grignard reagents, the carbon atom bonded to the magnesium is considered to have a partial negative charge due to the polar covalent bond between carbon and magnesium. This is because magnesium is less electronegative than carbon.

Assign oxidation numbers: In organic compounds, carbon typically has an oxidation number of -4 to +4. For the carbon in the Grignard reagent, it is more electronegative than magnesium, so it 'takes' the electrons from the Mg-C bond, giving it an oxidation number of -1.

Consider the aromatic ring: The carbon atom in the phenyl group is part of an aromatic ring, which does not affect the oxidation number of the carbon directly bonded to magnesium. The aromaticity is maintained, and the oxidation number calculation focuses on the direct bond with magnesium.

Summarize the oxidation number: The oxidation number of the carbon atom indicated by the arrow in the Grignard reagent is -1, due to its bond with the less electronegative magnesium.

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Key Concepts

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

Oxidation Number

The oxidation number is a theoretical charge assigned to an atom in a molecule, representing the number of electrons lost or gained by the atom. It helps in determining the electron distribution in compounds and is crucial for redox reactions. In organic chemistry, it aids in understanding the electron flow in reactions involving organometallic compounds like Grignard reagents.

Grignard Reagent

Grignard reagents are organomagnesium compounds typically represented as R-MgX, where R is an organic group and X is a halogen. They are highly reactive and used in forming carbon-carbon bonds. The magnesium atom in Grignard reagents often has a positive oxidation state, which is essential for understanding its reactivity and interaction with other molecules.

Electronegativity

Electronegativity is the tendency of an atom to attract electrons towards itself in a chemical bond. It influences the oxidation number by affecting electron distribution in a molecule. In the context of the image, understanding the electronegativity difference between magnesium and bromine helps determine the oxidation state of magnesium in the MgBr group attached to the benzene ring.

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