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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3:28 minutes

Problem 28f

Textbook Question

For each solvent, indicate the most likely substitution reaction to take place.
(f)

Verified step by step guidance

Step 1: Understand the two main types of substitution reactions: SN1 and SN2. SN1 reactions are unimolecular and proceed via a carbocation intermediate, while SN2 reactions are bimolecular and involve a single concerted step where the nucleophile attacks the substrate as the leaving group departs.

Step 2: Analyze the solvent provided in the problem. Solvents play a critical role in determining whether an SN1 or SN2 reaction is favored. Polar protic solvents (e.g., water, alcohols) stabilize carbocations and favor SN1 reactions, while polar aprotic solvents (e.g., acetone, DMSO) do not stabilize carbocations and favor SN2 reactions.

Step 3: Consider the substrate structure. Tertiary substrates typically favor SN1 reactions due to the stability of the carbocation intermediate, while primary substrates favor SN2 reactions due to steric hindrance being minimal. Secondary substrates can undergo either SN1 or SN2 depending on the solvent and nucleophile.

Step 4: Evaluate the nucleophile strength. Strong nucleophiles (e.g., OH⁻, CN⁻) favor SN2 reactions, while weak nucleophiles (e.g., H₂O, ROH) are more likely to participate in SN1 reactions.

Step 5: Combine the solvent type, substrate structure, and nucleophile strength to predict the most likely substitution reaction. For example, if the solvent is polar protic, the substrate is tertiary, and the nucleophile is weak, an SN1 reaction is most likely. Conversely, if the solvent is polar aprotic, the substrate is primary, and the nucleophile is strong, an SN2 reaction is most likely.

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Key Concepts

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

Nucleophilic Substitution Reactions

Nucleophilic substitution reactions involve the replacement of a leaving group in a molecule by a nucleophile. These reactions can occur via two main mechanisms: SN1, which is unimolecular and involves a carbocation intermediate, and SN2, which is bimolecular and involves a direct attack by the nucleophile. The choice of mechanism often depends on the structure of the substrate and the nature of the solvent.

Solvent Effects on Reaction Mechanisms

The solvent can significantly influence the rate and mechanism of nucleophilic substitution reactions. Polar protic solvents stabilize carbocations and can favor SN1 mechanisms, while polar aprotic solvents enhance the nucleophilicity of the nucleophile, often favoring SN2 mechanisms. Understanding the solvent's properties is crucial for predicting the outcome of substitution reactions.

Leaving Group Ability

The ability of a leaving group to depart from a substrate is a critical factor in substitution reactions. Good leaving groups, such as halides or sulfonate esters, can stabilize the transition state and facilitate the reaction. The strength of the bond between the leaving group and the substrate, as well as the stability of the leaving group after departure, are key considerations in determining the likelihood of a substitution reaction.

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