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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5:27 minutes

Problem 6b

Textbook Question

Propose a mechanism for the reaction of benzoic acid with acetyl chloride to give acetic benzoic anhydride.

Verified step by step guidance

Step 1: Identify the reactants and the product. The reactants are benzoic acid (C₆H₅COOH) and acetyl chloride (CH₃COCl), and the product is acetic benzoic anhydride (C₆H₅COOCOCH₃). This is an acylation reaction where an acid chloride reacts with a carboxylic acid to form an anhydride.

Step 2: Recognize the role of acetyl chloride as an electrophile. The carbonyl carbon in acetyl chloride is highly electrophilic due to the electron-withdrawing effect of the chlorine atom. Benzoic acid acts as a nucleophile, with the oxygen atom of the hydroxyl group attacking the electrophilic carbonyl carbon of acetyl chloride.

Step 3: Describe the nucleophilic attack. The lone pair of electrons on the oxygen atom of the hydroxyl group in benzoic acid attacks the carbonyl carbon of acetyl chloride, forming a tetrahedral intermediate. This intermediate is unstable and will collapse to eliminate a leaving group.

Step 4: Explain the elimination of the leaving group. The tetrahedral intermediate collapses, expelling the chloride ion (Cl⁻) as the leaving group. This results in the formation of a mixed anhydride intermediate, where the benzoic acid and acetyl groups are connected.

Step 5: Finalize the mechanism. The mixed anhydride intermediate stabilizes to form acetic benzoic anhydride, completing the reaction. The product contains two carbonyl groups connected by an oxygen atom, characteristic of an anhydride.

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Key Concepts

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

Acid-Base Reactions

In organic chemistry, acid-base reactions involve the transfer of protons (H+) between molecules. In the context of the reaction between benzoic acid and acetyl chloride, benzoic acid acts as a Brønsted acid, donating a proton to the acetyl chloride, which is a reactive acyl chloride. This step is crucial for initiating the formation of the anhydride product.

Nucleophilic Acyl Substitution

Nucleophilic acyl substitution is a fundamental reaction mechanism in organic chemistry where a nucleophile attacks an acyl compound, leading to the substitution of a leaving group. In this case, the hydroxyl group from benzoic acid acts as a nucleophile, attacking the carbonyl carbon of acetyl chloride, facilitating the formation of the acetic benzoic anhydride.

Formation of Anhydrides

Anhydrides are formed through the condensation of two carboxylic acids or a carboxylic acid and an acyl chloride, resulting in the loss of water. The reaction between benzoic acid and acetyl chloride exemplifies this process, where the hydroxyl group from benzoic acid and the chloride from acetyl chloride are eliminated, yielding acetic benzoic anhydride as the product.

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Related Practice

Textbook Question

Show how you would use appropriate acyl chlorides and amines to synthesize the following amides.

(d)

Textbook Question

Show how you would synthesize the following esters from appropriate acyl chlorides and alcohols.

(a) ethyl propionate

(b) phenyl 3-methylhexanoate

Textbook Question

Which of the following proposed reactions would take place quickly under mild conditions?

(a)

(b)

(c)

(d)

(e)

Textbook Question

Propose a mechanism for the reaction of aniline with acetic anhydride to give acetanilide.

Textbook Question

Propose a mechanism for the reaction of benzyl alcohol with acetyl chloride to give benzyl acetate.

Textbook Question

Show how you would accomplish the following synthetic conversions efficiently and in good yield. You may use any necessary additional reagents and solvents.

(g)

Textbook Question

Show how you would use an acid chloride as an intermediate to synthesize.

(a) N-phenylbenzamide (PhCONHPh) from benzoic acid and aniline.

Textbook Question

Show how you would convert the following starting materials to the indicated nitriles:

(a) phenylacetic acid → phenylacetonitrile

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