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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2:08 minutes

Problem 12c

Textbook Question

Show how you would use a Strecker synthesis to make
(c) aspartic acid.

Verified step by step guidance

Identify the starting materials for the Strecker synthesis. Strecker synthesis involves the reaction of an aldehyde (or ketone), ammonia (NH₃), and hydrogen cyanide (HCN) to form an α-amino nitrile, which is then hydrolyzed to produce an α-amino acid. For aspartic acid, the aldehyde should have a structure that leads to the desired amino acid upon synthesis.

Choose the appropriate aldehyde. Aspartic acid has a carboxylic acid group on both the α and β carbons. Therefore, the starting aldehyde should be oxaloacetaldehyde (CHO-CH₂-COOH), which contains the necessary carbon skeleton.

React the aldehyde with ammonia (NH₃) and hydrogen cyanide (HCN). This step forms an α-amino nitrile intermediate. The reaction mechanism involves the nucleophilic addition of HCN to the aldehyde, followed by the reaction of the resulting imine with NH₃ to form the α-amino nitrile.

Hydrolyze the α-amino nitrile. Treat the α-amino nitrile with aqueous acid (H₃O⁺) or base (OH⁻) to hydrolyze the nitrile group (-C≡N) into a carboxylic acid (-COOH). This step converts the intermediate into aspartic acid.

Verify the structure of the product. Ensure that the final product has the correct structure of aspartic acid, which is HOOC-CH(NH₂)-CH₂-COOH, with both carboxylic acid groups and the amino group in the correct positions.

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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 through the reaction of an aldehyde with ammonia and potassium cyanide. This process involves the formation of an α-amino nitrile intermediate, which can be hydrolyzed to yield the corresponding amino acid. It is particularly useful for producing α-amino acids, such as aspartic acid, from simple starting materials.

Amino Acids

Amino acids are organic compounds that serve as the building blocks of proteins. They contain an amino group (-NH2), a carboxyl group (-COOH), and a unique side chain (R group) that determines the properties of each amino acid. Aspartic acid is a non-essential amino acid that plays a critical role in the biosynthesis of proteins and is involved in various metabolic processes.

Hydrolysis

Hydrolysis is a chemical reaction that involves the breaking of a bond in a molecule using water. In the context of Strecker synthesis, hydrolysis converts the α-amino nitrile intermediate into the corresponding amino acid by adding water, which cleaves the nitrile group and forms the carboxylic acid and amino group. This step is essential for obtaining the final product, aspartic acid, from the initial reaction.

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Textbook Question

Show the peptides that would result from cleavage by the indicated reagent:

a. Val-Arg-Gly-Met-Arg-Ala-Ser by carboxypeptidase A

b. Ser-Phe-Lys-Met-Pro-Ser-Ala-Asp by cyanogen bromide

c. Arg-Ser-Pro-Lys-Lys-Ser-Glu-Gly by trypsin

Textbook Question

Show how valine can be prepared by

d. a N-phthalimidomalonic ester synthesis.

Textbook Question

Provide a synthesis of the following amino acids using a combination of the HVZ and amination reactions.

b. Leu

Textbook Question

Show how you would synthesize the following amino acids using the Strecker amino acid synthesis.

a. Ala

Textbook Question

Show how you would use the Strecker synthesis to make tryptophan. What stereochemistry would you expect in your synthetic product?

Textbook Question

Erwin Chargaff’s discovery that DNA contains equimolar amounts of guanine and cytosine and also equimolar amounts of adenine and thymine has come to be known as Chargaff’s rule:

G = C and A = T

(a) Does Chargaff’s rule imply that equal amounts of guanine and adenine are present in DNA? That is, does G = A?

(b) Does Chargaff’s rule imply that the sum of the purine residues equals the sum of the pyrimidine residues? That is, does A + G = C + T?

(c) Does Chargaff’s rule apply only to double-stranded DNA, or would it also apply to each individual strand if the double helical strand were separated into its two complementary strands?

Textbook Question

Show how you would use a Strecker synthesis to make phenylalanine.

Textbook Question

Propose a mechanism for each step in the synthesis in part (a).

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