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

8. Elimination Reactions

Cumulative Substitution/Elimination

Organic Chemistry

8. Elimination Reactions

Cumulative Substitution/Elimination

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Problem 106c(ii)

Textbook Question

Predict the product(s) that would result when molecules (a)–(p) are allowed to react under the following conditions: (ii) PBr₃ If no reaction occurs, write 'no reaction.'
(c)

Verified step by step guidance

Identify the functional groups in the given molecule. The structure shows a cyclohexane ring with two hydroxyl groups (OH) attached, indicating it is a diol.

Understand the role of PBr₃ in organic reactions. Phosphorus tribromide (PBr₃) is commonly used to convert alcohols into alkyl bromides by replacing the hydroxyl group with a bromine atom.

Determine which hydroxyl group will react with PBr₃. PBr₃ typically reacts with primary and secondary alcohols. In this molecule, both hydroxyl groups are secondary, so both can potentially react.

Predict the reaction mechanism. The reaction with PBr₃ involves the formation of a phosphite ester intermediate, followed by the substitution of the hydroxyl group with a bromine atom, resulting in the formation of an alkyl bromide.

Consider the stereochemistry of the reaction. The reaction with PBr₃ usually proceeds with inversion of configuration at the carbon atom bearing the hydroxyl group, due to the SN2 mechanism involved.

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Key Concepts

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

PBr₃ Reaction with Alcohols

Phosphorus tribromide (PBr₃) is commonly used to convert alcohols into alkyl bromides. The reaction involves the substitution of the hydroxyl group (OH) with a bromine atom (Br), resulting in the formation of an alkyl bromide. This reaction is typically used for primary and secondary alcohols, as it proceeds via an SN2 mechanism, which is less favorable for tertiary alcohols due to steric hindrance.

SN2 Mechanism

The SN2 mechanism is a bimolecular nucleophilic substitution reaction where the nucleophile attacks the electrophilic carbon from the opposite side of the leaving group, resulting in an inversion of configuration. This mechanism is favored in primary and secondary alcohols due to less steric hindrance, allowing the nucleophile to effectively approach the carbon atom. In the context of PBr₃ reactions, the bromide ion acts as the nucleophile, replacing the hydroxyl group.

Vicinal Diols

Vicinal diols are compounds with two hydroxyl groups attached to adjacent carbon atoms. In the given structure, the presence of vicinal diols can influence the reaction pathway, as they may undergo rearrangement or elimination under certain conditions. However, with PBr₃, each hydroxyl group can independently react to form the corresponding alkyl bromide, assuming no rearrangement occurs.

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Related Practice

Textbook Question

Predict the product(s) that would result when molecules (a)–(p) are allowed to react under the following conditions: (v) 1. TsCl, Et₃N 2. NaOt-Bu (vi) H₂SO₄ If no reaction occurs, write 'no reaction.'

(o)

Textbook Question

(k)

Textbook Question

Predict the product(s) that would result when molecules (a)–(p) are allowed to react under the following conditions: (vi) H₂SO₄. If no reaction occurs, write 'no reaction.'

(c)

Textbook Question

Predict the product(s) that would result when molecules (a)–(p) are allowed to react under the following conditions: (i) SOCl₂ ; (iii) SOCl₂, NEt₃. If no reaction occurs, write 'no reaction.'

(c)

Textbook Question

Predict the product(s) that would result when molecules (a)–(p) are allowed to react under the following conditions: (vii) HCl; (viii) HBr; If no reaction occurs, write 'no reaction.'

(c)

Textbook Question

(f)

Textbook Question

Predict the product(s) of the following substitution or elimination reactions, paying close attention to the stereochemical outcome of the reactions.

(a)

Textbook Question

Predict the product(s) of the following substitution or elimination reactions, paying close attention to the stereochemical outcome of the reactions.

(d)

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Predict the product(s) that would result when molecules (a)–(p) are allowed to react under the following conditions: (ii) PBr₃ If no reaction occurs, write 'no reaction.'(c)

Key Concepts

PBr₃ Reaction with Alcohols

SN2 Mechanism

Vicinal Diols

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Predict the product(s) that would result when molecules (a)–(p) are allowed to react under the following conditions: (ii) PBr₃ If no reaction occurs, write 'no reaction.'
(c)