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

2. Molecular Representations

Functional Groups

Organic Chemistry

2. Molecular Representations

Functional Groups

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5:47 minutes

Problem 65c,d

Textbook Question

Macrolide antibiotics all have large rings (macrocycle) in which an ester makes the ring; a cyclic ester is termed a lactone. One example is erythromycin A, first isolated from soil bacteria in the 1950s. Over time, some pathogenic bacteria have developed resistance to erythromycin by evolving an enzymatic mechanism to cleave the macrocycle at the ketone. To counter this resistance, chemists modified the erythromycin structure to replace the ketone with an amine that the bacteria could not detoxify. This modified antibiotic, azithromycin, trade name Zithromax®, is one of the most prescribed drugs in the world for respiratory infections.

(c) Identify the ketone in erythromycin targeted by bacteria as the site for detoxification.
(d) Identify the amine in azithromycin. What type of amine is it?

Verified step by step guidance

Examine the structure of erythromycin A. Look for a carbonyl group (C=O) within the macrocyclic ring, as this is the ketone targeted by bacteria.

In the erythromycin A structure, identify the ketone group. It is located at the top of the macrocyclic ring, where a carbon atom is double-bonded to an oxygen atom.

Now, examine the structure of azithromycin. Look for an amine group, which is a nitrogen atom bonded to one or more alkyl or aryl groups.

In the azithromycin structure, identify the amine group. It is located at the top of the macrocyclic ring, where a nitrogen atom is bonded to two methyl groups.

Determine the type of amine in azithromycin. Since the nitrogen is bonded to two carbon atoms (methyl groups) and one hydrogen atom, it is a secondary amine.

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Key Concepts

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

Macrolide Antibiotics

Macrolide antibiotics are a class of antibiotics characterized by their large macrocyclic lactone ring structure. They are effective against a variety of bacterial infections by inhibiting protein synthesis. Erythromycin is a well-known example, and its structure includes a ketone that can be targeted by bacterial resistance mechanisms.

Ketones and Amines

Ketones are organic compounds containing a carbonyl group (C=O) bonded to two carbon atoms, while amines are derivatives of ammonia (NH3) where one or more hydrogen atoms are replaced by alkyl or aryl groups. In the context of erythromycin and azithromycin, the ketone in erythromycin is the target for bacterial detoxification, while the amine in azithromycin serves as a modification to evade this resistance.

Bacterial Resistance Mechanisms

Bacterial resistance mechanisms refer to the various strategies that bacteria develop to survive exposure to antibiotics. In the case of erythromycin, bacteria evolved an enzymatic mechanism to cleave the macrocycle at the ketone, rendering the antibiotic ineffective. Understanding these mechanisms is crucial for developing new antibiotics, such as azithromycin, which incorporates structural changes to avoid being targeted.