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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2:38 minutes

Problem 12b

Textbook Question

Show how you would use a Strecker synthesis to make
(b) valine.

Verified step by step guidance

Step 1: Understand the Strecker synthesis process. Strecker synthesis is a method for synthesizing α-amino acids by reacting an aldehyde (or ketone), ammonia (or ammonium chloride), and hydrogen cyanide (HCN). The reaction proceeds through the formation of an imine intermediate followed by cyanohydrin formation and hydrolysis.

Step 2: Identify the target amino acid structure. Valine is an α-amino acid with the structure: (CH3)2CH-CH(NH3+)-COO−. This indicates that the starting aldehyde should have a branched alkyl group to match the valine side chain.

Step 3: Choose the appropriate aldehyde. To synthesize valine, the aldehyde used should be isobutyraldehyde ((CH3)2CHCHO), as it provides the correct branched alkyl group for the valine side chain.

Step 4: Perform the Strecker synthesis. React isobutyraldehyde with ammonia (NH3) and hydrogen cyanide (HCN). First, the aldehyde reacts with ammonia to form an imine intermediate. Then, the imine reacts with HCN to form an α-aminonitrile intermediate.

Step 5: Hydrolyze the α-aminonitrile. The α-aminonitrile is hydrolyzed under acidic conditions to yield the α-amino acid, valine. This step converts the nitrile group (-CN) into a carboxylic acid (-COOH), completing the synthesis.

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Key Concepts

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

Strecker Synthesis

Strecker synthesis is a method for synthesizing amino acids from aldehydes or ketones. It involves the reaction of an aldehyde with ammonia and hydrogen cyanide, leading to the formation of an α-amino nitrile, which can be hydrolyzed to yield the corresponding amino acid. This process is significant in organic chemistry for constructing amino acids, which are the building blocks of proteins.

Amino Acid Structure

Amino acids are organic compounds characterized by the presence of both an amino group (-NH2) and a carboxyl group (-COOH), along with a unique side chain (R group) that determines the properties of the amino acid. In the case of valine, the side chain is isopropyl, making it a branched-chain amino acid. Understanding the structure of amino acids is crucial for grasping their roles in biochemistry and protein synthesis.

Hydrolysis

Hydrolysis is a chemical reaction involving the breaking of a bond in a molecule using water. In the context of Strecker synthesis, hydrolysis is used to convert the α-amino nitrile intermediate into the corresponding amino acid. This step is essential for completing the synthesis process and obtaining the desired amino acid product, such as valine, from the initial reactants.