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

SN1 Reaction

Organic Chemistry

7. Substitution Reactions

SN1 Reaction

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6:32 minutes

Problem 1

Textbook Question

Rank the ability of the following compounds to undergo an S_N1 reaction ( 1 = fastest, 5 = slowest ).

Verified step by step guidance

Step 1: Recall the key factors that influence the rate of an S_N1 reaction. The S_N1 mechanism involves the formation of a carbocation intermediate, so the stability of the carbocation is the most critical factor. More stable carbocations lead to faster S_N1 reactions.

Step 2: Analyze the structure of each compound provided in the problem. Identify the leaving group and the carbon atom to which it is attached. Consider the type of carbocation that would form if the leaving group departs (e.g., primary, secondary, tertiary, allylic, or benzylic).

Step 3: Rank the stability of the carbocations that would form. Tertiary carbocations are more stable than secondary carbocations, which are more stable than primary carbocations. Additionally, carbocations stabilized by resonance (e.g., allylic or benzylic) are more stable than those without resonance stabilization.

Step 4: Consider any additional factors that might influence the reaction rate, such as the quality of the leaving group (better leaving groups facilitate faster reactions) and the solvent (polar protic solvents stabilize the carbocation and favor S_N1 reactions).

Step 5: Based on the analysis of carbocation stability and other factors, rank the compounds from fastest to slowest in their ability to undergo an S_N1 reaction. Assign 1 to the compound with the fastest reaction rate and 5 to the compound with the slowest reaction rate.

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Key Concepts

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

S_N1 Mechanism

The S_N1 (substitution nucleophilic unimolecular) mechanism involves a two-step process where the rate-determining step is the formation of a carbocation intermediate. The reaction rate depends solely on the concentration of the substrate, not the nucleophile. This mechanism is favored by tertiary substrates due to their ability to stabilize the carbocation through hyperconjugation and inductive effects.

Carbocation Stability

Carbocation stability is crucial in S_N1 reactions, as more stable carbocations form more readily and lead to faster reactions. Stability increases in the order of primary < secondary < tertiary, with resonance also playing a significant role. Compounds that can delocalize the positive charge through resonance structures will have enhanced stability and thus a higher likelihood of undergoing S_N1 reactions.

Solvent Effects

The choice of solvent significantly influences the rate of S_N1 reactions. Polar protic solvents stabilize the carbocation and the leaving group, facilitating the reaction. These solvents can also solvate the nucleophile, affecting its reactivity. Therefore, understanding solvent interactions is essential for predicting the reaction rate and ranking the compounds in an S_N1 context.

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Related Practice

Textbook Question

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

(a)

Textbook Question

Which of the following S_N1 reactions should proceed at a faster rate? Justify your answer on a reaction coordinate diagram.

Textbook Question

Practice your electron-pushing skills by drawing a mechanism for the following S_N1 reactions.

(a)

Textbook Question

The allylic bromide below gives two S_N1 products. Justify the formation of each.

Textbook Question

Propose a mechanism for each reaction, showing explicitly how the observed mixtures of products are formed.

(b) 2-methylbut-3-en-2-ol + HBr → 1-bromo-3-methylbut-2-ene + 3-bromo-3-methylbut-1-ene

Textbook Question

Treatment of an alkyl halide with AgNO₃ in alcohol often promotes ionization.

Ag⁺ + R–Cl → AgCl + R⁺

When 4-chloro-2-methylhex-2-ene reacts with AgNO₃ in ethanol, two isomeric ethers are formed. Suggest structures, and propose a mechanism for their formation

Textbook Question

When 3-bromo-1-methylcyclohexene undergoes solvolysis in hot ethanol, two products are formed. Propose a mechanism that accounts for both of these products.

Textbook Question

Which haloalkane would you expect to undergo the fastest S_N1 reaction? Why?

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