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

7. Substitution Reactions

Substitution Comparison

Organic Chemistry

7. Substitution Reactions

Substitution Comparison

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Problem 32b

Textbook Question

Provide a mechanism for the following S_N1 reactions that feature a rearrangement.
(b)

Verified step by step guidance

Step 1: Identify the reaction type. This is an SN1 reaction, which proceeds via a two-step mechanism involving the formation of a carbocation intermediate.

Step 2: The first step is the departure of the leaving group (Cl⁻) from the substrate, forming a carbocation. The substrate is benzyl chloride, and the benzyl group stabilizes the carbocation through resonance.

Step 3: Analyze the carbocation intermediate for possible rearrangements. In this case, a hydride shift occurs to form a more stable tertiary carbocation. The hydride shift involves the migration of a hydrogen atom with its bonding electrons from an adjacent carbon to the carbocation center.

Step 4: Once the tertiary carbocation is formed, the nucleophile (acetic acid, CH₃COOH) attacks the carbocation. The oxygen atom in acetic acid donates a lone pair of electrons to form a bond with the carbocation.

Step 5: The final step involves deprotonation of the intermediate formed after nucleophilic attack, resulting in the formation of the product, which is an ester with a phenyl group and a tertiary carbon center.

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Key Concepts

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

Sₙ1 Reaction Mechanism

The Sₙ1 (substitution nucleophilic unimolecular) reaction mechanism involves a two-step process where the first step is the formation of a carbocation intermediate after the leaving group departs. This intermediate is then attacked by a nucleophile in the second step. The rate of the reaction depends only on the concentration of the substrate, making it unimolecular.

Carbocation Stability and Rearrangement

Carbocations are positively charged species that can undergo rearrangement to form more stable structures. Stability increases with the degree of substitution (tertiary > secondary > primary). Rearrangement can occur through hydride or alkyl shifts, allowing the carbocation to transition to a more stable form before the nucleophilic attack.

Nucleophilic Attack

Nucleophilic attack is the process where a nucleophile donates a pair of electrons to an electrophile, forming a new bond. In Sₙ1 reactions, this occurs after the formation of the carbocation. The nucleophile can attack from either side of the planar carbocation, leading to potential stereochemical outcomes, including racemization if the substrate is chiral.

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Textbook Question

cis-4-Bromocyclohexanol and trans-4-bromocyclohexanol form the same elimination product but a different substitution product when they react with HO⁻.

b. Explain, by showing the mechanisms, why different substitution products are obtained.

Textbook Question

When equivalent amounts of methyl bromide and sodium iodide are dissolved in methanol, the concentration of iodide ion quickly decreases and then slowly returns to its original concentration. Account for this observation.

Textbook Question

Provide an arrow-pushing mechanism that rationalizes the outcome of the reaction shown.

Textbook Question

Optically active 2-bromobutane undergoes racemization on treatment with a solution of KBr. Propose a mechanism for this racemization.

Textbook Question

Suggest a mechanism for the following substitution reactions.

(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.'

(o)

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.'

(k)

Textbook Question

What stereoisomers does the following reaction form?

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