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

22. Carboxylic Acid Derivatives: NAS

Nucleophilic Acyl Substitution

Organic Chemistry

22. Carboxylic Acid Derivatives: NAS

Nucleophilic Acyl Substitution

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5:21 minutes

Problem 67a

Textbook Question

a. Rank the following esters from most reactive to least reactive in the first slow step of a nucleophilic acyl substitution reaction (formation of the tetrahedral intermediate):

Verified step by step guidance

Step 1: Understand the reactivity of esters in nucleophilic acyl substitution reactions. The first slow step involves the attack of a nucleophile on the carbonyl carbon, forming a tetrahedral intermediate. The reactivity depends on the electronic effects of substituents attached to the ester group.

Step 2: Analyze the substituents attached to the ester oxygen in each compound. Electron-withdrawing groups (EWGs) increase the electrophilicity of the carbonyl carbon, making it more reactive. Electron-donating groups (EDGs) decrease the electrophilicity, making the ester less reactive.

Step 3: Examine compound A. It has a chlorine atom attached to a benzene ring, which is an electron-withdrawing group. This increases the reactivity of the ester by stabilizing the partial positive charge on the carbonyl carbon.

Step 4: Examine compound B. It has a cyclohexyl group, which is an electron-donating group. This decreases the reactivity of the ester by reducing the electrophilicity of the carbonyl carbon.

Step 5: Compare compound C and D. Compound C has a benzene ring, which is less electron-withdrawing than the chlorinated benzene ring in compound D. Compound D has two chlorine atoms attached to the benzene ring, making it the most electron-withdrawing and therefore the most reactive ester in the series.

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Key Concepts

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

Nucleophilic Acyl Substitution

Nucleophilic acyl substitution is a fundamental reaction in organic chemistry where a nucleophile attacks the carbonyl carbon of an acyl compound, leading to the formation of a tetrahedral intermediate. This reaction is characterized by the replacement of a leaving group (often a carboxylic acid derivative) with a nucleophile. The reactivity of the acyl compound is influenced by the nature of the leaving group and the electronic effects of substituents on the carbonyl carbon.

Reactivity of Esters

The reactivity of esters in nucleophilic acyl substitution is determined by the stability of the leaving group and the electronic environment around the carbonyl. Electron-withdrawing groups, such as halogens, increase the electrophilicity of the carbonyl carbon, making the ester more reactive. Conversely, electron-donating groups can decrease reactivity by stabilizing the carbonyl, making it less susceptible to nucleophilic attack.

Tetrahedral Intermediate

The tetrahedral intermediate is a key species formed during nucleophilic acyl substitution. It results from the nucleophile's attack on the carbonyl carbon, leading to a temporary four-coordinate structure. The stability of this intermediate is crucial for the reaction's progression; if it is stable, the reaction is more likely to proceed to completion, while an unstable intermediate may lead to a slower reaction or revert to starting materials.

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Related Practice

Textbook Question

a. Which of the following reactions does not give the carbonyl product shown?

b. Which of the reactions that do not occur can be made to occur if an acid catalyst is added to the reaction mixture?

Textbook Question

a. Which of the following reactions does not give the carbonyl product shown?

b. Which of the reactions that do not occur can be made to occur if an acid catalyst is added to the reaction mixture?

10.

Textbook Question

b. Explain why the rate of aminolysis of an ester cannot be increased by H⁺.

Textbook Question

b. Explain why the rate of aminolysis of an ester cannot be increased by HO⁻, or RO⁻.

Textbook Question

b. Rank the same esters from most reactive to least reactive in the second slow step of a nucleophilic acyl substitution reaction (collapse of the tetrahedral intermediate).

Textbook Question

In each part, rank the compounds in order of increasing rate of nucleophilic attack at C=O by a strong nucleophile like methoxide.

(a)

Textbook Question

Show how you would convert 2-methylcyclopentanol to the following products. Any of these products may be used as the reactant in any subsequent part of this problem.

(g) 2-methylcyclopentyl acetate

(h) 1-bromo-1-methylcyclopentane

Textbook Question

Predict the product of the multistep synthesis reaction shown.

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