Textbook Question
Write the mechanism for the reaction of an amino acid with di-tert-butyl dicarbonate.
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Ch. 21 - Amino Acids, Peptides, and Proteins
Bruice8th EditionOrganic ChemistryISBN: 9780135213711
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Table of contents
- Ch. 1 - Remembering General Chemistry: Electronic Structure and Bonding (Part 1)31
- Ch. 1 - Remembering General Chemistry: Electronic Structure and Bonding (Part 2)65
- Ch. 2 - Acids and Bases: Central to Understanding Organic Chemistry84
- Ch. 3 - An Introduction to Organic Compounds:Nomenclature, Physical Properties, and Structure183
- Ch. 4 - Isomers: The Arrangement of Atoms in Space121
- Ch. 5 - Alkenes: Structure, Nomenclature, and an Introduction to Reactivity • Thermodynamics and Kinetics83
- Ch. 6 - The Reactions of Alkenes • The Stereochemistry of Addition Reactions175
- Ch. 7 - The Reactions of Alkynes • An Introduction to Multistep Synthesis119
- Ch. 8 - Delocalized Electrons: Their Effect on Stability, pKa, and the Products of a Reaction • Aromaticity and Electronic Effects: An Introduction to the Reactions of Benzene148
- Ch. 9 - Substitution and Elimination Reactions of Alkyl Halides212
- Ch. 10 - Reactions of Alcohols, Ethers, Epoxides, Amines, and Sulfur-Containing Compounds131
- Ch. 11 - Organometallic Compounds60
- Ch. 12 - Radicals90
- Ch. 13 - Mass Spectrometry; Infrared Spectroscopy; UV/Vis Spectroscopy62
- Ch. 14 - NMR Spectroscopy95
- Ch. 15 - Reactions of Carboxylic Acids and Carboxylic Acid Derivatives123
- Ch. 16 - Reactions of Aldehydes and Ketones • More Reactions of Carboxylic Acid Derivatives141
- Ch. 17 - Reactions at the Alpha-Carbon101
- Ch. 18 - Reactions of Benzene and Substituted Benzenes144
- Ch. 19 - More About Amines • Reactions of Heterocyclic Compounds49
- Ch. 20 - The Organic Chemistry of Carbohydrates80
- Ch. 21 - Amino Acids, Peptides, and Proteins57
- Ch. 22 - Catalysis in Organic Reactions and in Enzymatic Reactions35
- Ch. 23 - The Organic Chemistry of the Coenzymes—Compounds Derived from Vitamins1
- Ch. 28 - Pericyclic Reactions58
Chapter 22, Problem 68b,c
α-Amino acids can be prepared by treating an aldehyde with ammonia/trace acid, followed by hydrogen cyanide, followed by acid-catalyzed hydrolysis.
b. What amino acid is formed when the aldehyde that is used is 3-methylbutanal?
c. What aldehyde is needed to prepare isoleucine?
Verified step by step guidance1
Step 1: Understand the Strecker synthesis process. In this method, an aldehyde reacts with ammonia and trace acid to form an imine intermediate. Hydrogen cyanide then reacts with the imine to form an aminonitrile, which is hydrolyzed under acidic conditions to yield an α-amino acid.
Step 2: For part (b), identify the aldehyde used: 3-methylbutanal. This aldehyde has a branched structure with a methyl group on the third carbon of a butanal chain. The Strecker synthesis will add an amino group (-NH2) and a carboxylic acid group (-COOH) to the α-carbon of the aldehyde, forming the corresponding α-amino acid.
Step 3: Analyze the structure of 3-methylbutanal. The α-carbon of the aldehyde is adjacent to the carbonyl group. After the Strecker synthesis, the α-carbon will have an amino group and a carboxylic acid group, resulting in the formation of leucine, an α-amino acid with a branched side chain.
Step 4: For part (c), determine the aldehyde needed to prepare isoleucine. Isoleucine is an α-amino acid with a specific branched structure. To synthesize isoleucine via the Strecker synthesis, the aldehyde must have a structure that, after the addition of the amino and carboxylic acid groups, matches the side chain of isoleucine. The required aldehyde is 2-methylbutanal.
Step 5: Summarize the process. For part (b), 3-methylbutanal leads to leucine. For part (c), 2-methylbutanal is the aldehyde needed to prepare isoleucine. Both follow the Strecker synthesis mechanism, which involves imine formation, aminonitrile formation, and acid-catalyzed hydrolysis.
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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 characterized by the presence of an amino group (-NH2), a carboxyl group (-COOH), and a unique side chain (R group) that determines the properties of the amino acid. The general structure allows for the formation of proteins through peptide bonds, where the carboxyl group of one amino acid reacts with the amino group of another.
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Charged Amino Acids
Aldehyde Reactivity
Aldehydes are reactive carbonyl compounds that can undergo nucleophilic addition reactions. In the synthesis of amino acids, aldehydes react with ammonia to form imines, which can then be further processed with hydrogen cyanide and hydrolysis to yield amino acids. The specific aldehyde used influences the structure of the resulting amino acid.
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Synthesis of Isoleucine
Isoleucine is an essential amino acid that can be synthesized from specific aldehydes through a series of reactions. To prepare isoleucine, the appropriate aldehyde is 2-methylbutanal, which, when treated with ammonia and followed by hydrogen cyanide and hydrolysis, leads to the formation of isoleucine. Understanding the correct precursor is crucial for successful synthesis.
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1:16Synthesis of Amino Acids: Strecker Synthesis Example 1
Related Practice
Textbook Question
α-Amino acids can be prepared by treating an aldehyde with ammonia/trace acid, followed by hydrogen cyanide, followed by acid-catalyzed hydrolysis.
a. Draw the structures of the two intermediates formed in this reaction.
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Textbook Question
Glycine has pKa values of 2.3 and 9.6. Do you expect the pKa values of glycylglycine to be higher or lower than these values?
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Textbook Question
After the polypeptide shown below was treated with maleic anhydride, it was hydrolyzed by trypsin. (After a polypeptide is treated with maleic anhy- dride, trypsin will cleave the polypeptide only on the C-side of arginine.)
Gly-Ala-Asp-Ala-Leu-Pro-Gly-Ile-Leu-Val-Arg-Asp-Val-Gly-Lys-Val-Glu-Val-Phe-Glu-Ala-Gly- Arg-Ala-Glu-Phe-Lys-Glu-Pro-Arg-Leu-Val-Met-Lys-Val-Glu-Gly-Arg-Pro-Val-Gly-Ala-Gly-Leu-Trp
a. After a polypeptide is treated with maleic anhydride, why does trypsin no longer cleave it on the C-side of lysine?
b. How many fragments are obtained from the polypeptide?
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Textbook Question
Reaction of a polypeptide with carboxypeptidase A releases Met. The polypeptide undergoes partial hydrolysis to give the following peptides. What is the sequence of the polypeptide?
1. Ser, Lys, Trp
2. Gly, His, Ala
3. Glu, Val, Ser
4. Leu, Glu, Ser
5. Met, Ala, Gly
6. Ser, Lys, Val
7. Glu, His
8. Leu, Lys, Trp
9. Lys, Ser
10. Glu, His, Val
11. Trp, Leu, Glu
12. Ala, Met
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Textbook Question
Draw the product obtained when a lysine side chain in a polypeptide reacts with maleic anhydride.
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