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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9:47 minutes

Problem 67b

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).

Verified step by step guidance

Step 1: Understand the context of nucleophilic acyl substitution. The second slow step involves the collapse of the tetrahedral intermediate, where the leaving group departs and the carbonyl group reforms. The reactivity depends on the stability of the leaving group and the electronic effects of substituents on the ester.

Step 2: Analyze the substituents attached to the aromatic ring or alkyl group in each ester. Electron-withdrawing groups (EWGs) stabilize the negative charge on the leaving group, making the collapse of the tetrahedral intermediate faster. For example, chlorine atoms are strong EWGs.

Step 3: Compare the esters: (A) has a single chlorine substituent on the aromatic ring, (B) has no aromatic ring and is an alkyl ester, (C) has an unsubstituted aromatic ring, and (D) has two chlorine substituents on the aromatic ring. The presence of EWGs (like chlorine) on the aromatic ring increases reactivity.

Step 4: Rank the esters based on the number and position of EWGs. Ester D, with two chlorine substituents, is the most reactive due to the strong electron-withdrawing effect. Ester A, with one chlorine substituent, is next. Ester C, with an unsubstituted aromatic ring, follows. Ester B, an alkyl ester, is the least reactive as it lacks EWGs.

Step 5: Conclude the ranking: D > A > C > B. This ranking is based on the electronic effects of substituents influencing the stability of the leaving group during the collapse of the tetrahedral intermediate.

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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 intermediate can collapse, resulting in the substitution of the leaving group (often an alcohol or halide) with the nucleophile. Understanding this mechanism is crucial for predicting the reactivity of different acyl compounds, such as esters.

Reactivity of Esters

The reactivity of esters in nucleophilic acyl substitution is influenced by the nature of the substituents attached to the carbonyl carbon. 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. Thus, analyzing the substituents on the esters in the question is essential for ranking their reactivity.

Tetrahedral Intermediate Stability

The stability of the tetrahedral intermediate formed during nucleophilic acyl substitution plays a significant role in determining the overall reaction rate. Factors such as steric hindrance and electronic effects from substituents can affect the stability of this intermediate. A more stable intermediate will lead to a slower collapse and thus a slower reaction, while an unstable intermediate will collapse more readily, indicating higher reactivity.

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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?

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

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):

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.

Textbook Question

Predict the product of the following reaction sequences.

(a)

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