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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2:17 minutes

Problem 20a

Textbook Question

Would the following nucleophiles be more likely to participate in an S_N1 or S_N2 reaction?
(a)

Verified step by step guidance

Step 1: Analyze the structure of the nucleophile provided in the image. The nucleophile is tert-butanol (tert-butyl alcohol), which has a bulky tertiary structure with an -OH group attached to a central carbon atom surrounded by three methyl groups.

Step 2: Recall the key differences between SN1 and SN2 mechanisms. SN1 reactions involve a two-step process with the formation of a carbocation intermediate, and they are favored by tertiary substrates due to carbocation stability. SN2 reactions involve a one-step process where the nucleophile attacks the substrate directly, and they are hindered by steric bulk.

Step 3: Consider the steric hindrance of the nucleophile. The bulky tert-butyl group makes it difficult for the nucleophile to approach the electrophilic carbon in an SN2 reaction, as steric hindrance significantly slows down the direct backside attack required for SN2.

Step 4: Evaluate the stability of the carbocation intermediate. In an SN1 reaction, the tertiary structure of tert-butanol would lead to a highly stable carbocation intermediate, which favors the SN1 mechanism.

Step 5: Conclude that due to the steric hindrance and the stability of the carbocation intermediate, the nucleophile (tert-butanol) is more likely to participate in an SN1 reaction rather than an SN2 reaction.

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Key Concepts

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

Nucleophiles

Nucleophiles are species that donate an electron pair to form a chemical bond in a reaction. They are typically negatively charged or neutral molecules with lone pairs of electrons. The strength and reactivity of a nucleophile can influence whether a reaction proceeds via an Sₙ1 or Sₙ2 mechanism, with stronger nucleophiles favoring Sₙ2 reactions due to their ability to attack the electrophile directly.

Sₙ1 Mechanism

The Sₙ1 (substitution nucleophilic unimolecular) mechanism involves a two-step process where the leaving group departs first, forming a carbocation intermediate. This mechanism is favored in polar protic solvents and with tertiary substrates, as the stability of the carbocation is crucial. The nucleophile then attacks the carbocation in the second step, leading to the final product.

Sₙ2 Mechanism

The Sₙ2 (substitution nucleophilic bimolecular) mechanism is a one-step process where the nucleophile attacks the substrate simultaneously as the leaving group departs. This concerted mechanism requires strong nucleophiles and is favored by primary or secondary substrates in polar aprotic solvents. The reaction rate depends on both the nucleophile and the substrate, making it bimolecular.

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