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

29. Amino Acids

Amino Acid Chart

Organic Chemistry

29. Amino Acids

Amino Acid Chart

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2:46 minutes

Problem 1d

Textbook Question

Draw three-dimensional representations of the following amino acids.
(d) L-tryptophan

Verified step by step guidance

Understand the structure of L-tryptophan: L-tryptophan is an amino acid with a chiral center. It contains an indole functional group (a bicyclic structure with a benzene ring fused to a pyrrole ring), an amino group (-NH₂), a carboxylic acid group (-COOH), and a side chain attached to the alpha carbon.

Identify the stereochemistry: The 'L' designation indicates that the amino acid is in the L-configuration, which corresponds to the S-configuration for most amino acids (except cysteine). This means the groups around the alpha carbon are arranged in a specific three-dimensional orientation.

Position the groups around the alpha carbon: In a three-dimensional representation, place the alpha carbon at the center. Attach the carboxylic acid group (-COOH) above the plane, the amino group (-NH₂) to the left, the hydrogen atom below the plane, and the indole-containing side chain to the right. This arrangement follows the CORN rule when viewed with the hydrogen atom pointing away.

Draw the indole side chain: The side chain of tryptophan consists of a methylene group (-CH₂) attached to the alpha carbon, which is then connected to the indole group. Represent the indole group as a fused bicyclic structure with alternating double bonds in the benzene ring and a nitrogen atom in the pyrrole ring.

Finalize the three-dimensional drawing: Use wedge-and-dash notation to indicate the spatial arrangement of the groups. Solid wedges represent bonds coming out of the plane toward the viewer, dashed wedges represent bonds going behind the plane, and straight lines represent bonds in the plane. Ensure the stereochemistry matches the L-configuration.

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Key Concepts

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

Amino Acid Structure

Amino acids are organic compounds composed of a central carbon atom, an amino group (-NH2), a carboxyl group (-COOH), a hydrogen atom, and a variable side chain (R group). The side chain determines the unique properties of each amino acid, influencing its role in protein structure and function.

Chirality in Amino Acids

Most amino acids, except glycine, are chiral, meaning they exist in two enantiomeric forms that are mirror images of each other. The 'L' and 'D' nomenclature refers to the configuration around the chiral carbon, with L-forms being the predominant type found in proteins. Understanding chirality is essential for accurately representing amino acids in three-dimensional structures.

Three-Dimensional Molecular Representation

Three-dimensional representations of molecules, such as amino acids, can be depicted using various models, including ball-and-stick and space-filling models. These representations help visualize the spatial arrangement of atoms, bond angles, and molecular geometry, which are crucial for understanding the interactions and functions of amino acids in biological systems.

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