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 20e

Textbook Question

Would the following nucleophiles be more likely to participate in an S_N1 or S_N2 reaction?
(e) H₂O

Verified step by step guidance

Step 1: Understand the difference between SN1 and SN2 reactions. SN1 reactions are unimolecular nucleophilic substitution reactions that proceed through a carbocation intermediate, while SN2 reactions are bimolecular nucleophilic substitution reactions that occur in a single concerted step with a backside attack.

Step 2: Analyze the nucleophile, H₂O. Water (H₂O) is a weak nucleophile because it is neutral and does not have a strong negative charge to readily donate electrons. This makes it less effective in participating in SN2 reactions, which require strong nucleophiles.

Step 3: Consider the solvent effect. H₂O is also a polar protic solvent, which stabilizes carbocations and anions through hydrogen bonding. This stabilization favors the formation of a carbocation intermediate, making it more likely to participate in an SN1 reaction.

Step 4: Evaluate steric hindrance. Since H₂O is a small molecule, steric hindrance is not a significant factor. However, the weak nucleophilicity of H₂O still makes it more suited for SN1 reactions, where the rate-determining step does not depend on the nucleophile.

Step 5: Conclude that H₂O is more likely to participate in an SN1 reaction due to its weak nucleophilicity and its role as a polar protic solvent, which stabilizes the carbocation intermediate required for SN1 mechanisms.

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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 S_N1 or S_N2 mechanism.

S_N1 and S_N2 Mechanisms

S_N1 (unimolecular nucleophilic substitution) and S_N2 (bimolecular nucleophilic substitution) are two fundamental mechanisms of nucleophilic substitution reactions. S_N1 involves a two-step process where the leaving group departs first, forming a carbocation, followed by nucleophilic attack. In contrast, S_N2 is a one-step process where the nucleophile attacks the substrate simultaneously as the leaving group departs.

Carbocation Stability

Carbocation stability is crucial in determining the likelihood of an S_N1 reaction. More stable carbocations, such as tertiary carbocations, are favored in S_N1 mechanisms due to their lower energy and greater ability to stabilize the positive charge. Conversely, S_N2 reactions are favored by less sterically hindered substrates, as they require a direct attack by the nucleophile.

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Related Practice

Textbook Question

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

(f)

Textbook Question

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

(g)

Textbook Question

Predict the product of the following substitution reactions, paying close attention to the stereochemical outcome of the reactions.

(b)

Textbook Question

Predict the product of the following substitution reactions, paying close attention to the stereochemical outcome of the reactions.

(c)

Textbook Question

Fill in the squares in the following chemical equations:

Textbook Question

Fill in the squares in the following chemical equations:

Textbook Question

What substitution products are obtained when each of the following compounds is added to a solution of sodium acetate in acetic acid?

a. 2-chloro-2-methyl-3-hexene

b. 3-bromo-1-methylcyclohexene

Textbook Question

Draw the substitution products for each of the following S_N2 reactions. If the products can exist as stereoisomers, show which stereoisomers are formed:

a. (3S,4S)-3-bromo-4-methylhexane + CH₃O^-

b. (3S,4R)-3-bromo-4-methylhexane + CH₃O^-

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Would the following nucleophiles be more likely to participate in an SN1 or SN2 reaction?(e) H2O

Key Concepts

Nucleophiles

S_N1 and S_N2 Mechanisms

Carbocation Stability

Watch next

Would the following nucleophiles be more likely to participate in an S_N1 or S_N2 reaction?
(e) H₂O