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

Proteins and Amino Acids

Organic Chemistry

29. Amino Acids

Proteins and Amino Acids

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2:45 minutes

Problem 9a

Textbook Question

Show how the following amino acids might be formed in the laboratory by reductive amination of the appropriate α-ketoacid.
(a) alanine

Verified step by step guidance

Identify the structure of alanine. Alanine is an amino acid with the structure CH₃-CH(NH₂)-COOH. This means the α-ketoacid precursor must have a similar structure but with a keto group (C=O) instead of the amino group (NH₂).

Determine the α-ketoacid precursor. Replace the amino group (-NH₂) in alanine with a keto group (-C=O) to get the α-ketoacid. The resulting structure is pyruvic acid (CH₃-CO-COOH).

Understand the process of reductive amination. Reductive amination involves the reaction of an α-ketoacid with ammonia (NH₃) in the presence of a reducing agent, such as sodium cyanoborohydride (NaBH₃CN) or hydrogen gas (H₂) with a metal catalyst, to form an amino acid.

Write the reaction mechanism. In the first step, the α-ketoacid (pyruvic acid) reacts with ammonia to form an imine intermediate (CH₃-C=NH-COOH). This is a condensation reaction where water is eliminated.

Explain the reduction step. The imine intermediate is then reduced by the reducing agent (e.g., NaBH₃CN) to form alanine (CH₃-CH(NH₂)-COOH). This step adds hydrogen to the imine, converting the C=N bond into a C-NH₂ bond.

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Key Concepts

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

Reductive Amination

Reductive amination is a chemical reaction that involves the conversion of a carbonyl compound, such as an α-ketoacid, into an amine. This process typically involves the addition of an amine to the carbonyl group, followed by reduction, often using a reducing agent like sodium cyanoborohydride. This reaction is crucial for synthesizing amino acids from their corresponding keto acids.

α-Ketoacids

α-Ketoacids are organic compounds that contain a ketone functional group adjacent to a carboxylic acid group. They serve as important intermediates in various metabolic pathways and can be converted into amino acids through reductive amination. For alanine, the relevant α-ketoacid is pyruvate, which can be transformed into alanine by adding an amine group and reducing the carbonyl.

Amino Acid Structure

Amino acids are organic molecules that serve as the building blocks of proteins. Each amino acid has a central carbon atom bonded to an amino group, a carboxyl group, a hydrogen atom, and a variable R group that determines its unique properties. Understanding the structure of amino acids is essential for grasping how they are synthesized from α-ketoacids through reactions like reductive amination.

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Related Practice

Textbook Question

Show how valine can be prepared by

a. a Hell–Volhard–Zelinski reaction.

Textbook Question

Show how valine can be prepared by

c. a reductive amination.

Textbook Question

Which of the following C-terminal peptide bonds is more readily cleaved by carboxypeptidase A? Explain your choice.

Ser-Ala-Leu or Ser-Ala-Asp

Textbook Question

Show how you would synthesize any of the standard amino acids from each starting material. You may use any necessary reagents.

(a)

Textbook Question

Show how you would synthesize any of the standard amino acids from each starting material. You may use any necessary reagents.

(b)

Textbook Question

Show how you would use bromination followed by amination to synthesize the following amino acids.

(b) leucine

Textbook Question

The herbicide glyphosate (Roundup®) kills plants by inhibiting an enzyme needed for synthesis of phenylalanine. Deprived of phenylalanine, the plant cannot make the proteins it needs, and it gradually weakens and dies. Although a small amount of glyphosate is deadly to a plant, its human toxicity is quite low. Suggest why this powerful herbicide has little effect on humans.

Textbook Question

Give equations for the formation and hydrogenolysis of N-benzyloxycarbonyl methionine.

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Show how the following amino acids might be formed in the laboratory by reductive amination of the appropriate α-ketoacid. (a) alanine

Key Concepts

Reductive Amination

α-Ketoacids

Amino Acid Structure

Watch next

Show how the following amino acids might be formed in the laboratory by reductive amination of the appropriate α-ketoacid.
(a) alanine