Textbook Question
Show how you would use a Strecker synthesis to make
(b) valine.
1
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Ch. 24 - Amino Acids, Peptides, and Proteins
Wade9th EditionOrganic ChemistryISBN: 9780135213728
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Table of contents
- Ch.1 - Structure and Bonding107
- Ch. 2 - Acids and Bases; Functional Groups115
- Ch.3 - Structure and Stereochemistry of Alkanes100
- Ch.4 - The Study of Chemical Reactions99
- Ch.5 - Stereochemistry93
- Ch.6 - Alkyl Halides; Nucleophilic Substitution118
- Ch. 7 - Structure and Synthesis of Alkenes; Elimination158
- Ch.8 - Reactions of Alkenes171
- Ch.9 - Alkynes91
- Ch.10 - Structure and Synthesis of Alcohols143
- Ch.11 - Reactions of Alcohols104
- Ch. 12 - Infrared Spectroscopy and Mass Spectrometry22
- Ch. 13 - Nuclear Magnetic Resonance Spectroscopy45
- Ch. 14 - Ethers, Epoxides, and Thioethers72
- Ch. 15 - Conjugated Systems, Orbital Symmetry, and Ultraviolet Spectroscopy89
- Ch. 16 - Aromatic Compounds74
- Ch. 17 - Reactions of Aromatic Compounds126
- Ch. 18 - Ketones and Aldehydes193
- Ch. 19 - Amines129
- Ch. 20 - Carboxylic Acids77
- Ch. 21 - Carboxylic Acid Derivatives141
- Ch. 22 - Condensations and Alpha Substitutions of Carbonyl Compounds175
- Ch. 23 - Carbohydrates and Nucleic Acids93
- Ch. 24 - Amino Acids, Peptides, and Proteins54
Chapter 24, Problem 11a
Show how you would use a Strecker synthesis to make phenylalanine.
Verified step by step guidance1
Identify the starting materials for Strecker synthesis: Strecker synthesis involves the reaction of an aldehyde (or ketone), ammonia (NH₃), and hydrogen cyanide (HCN) to form an α-amino acid. For phenylalanine, the aldehyde needed is benzaldehyde (C₆H₅CHO).
React benzaldehyde with ammonia and hydrogen cyanide: In the first step, benzaldehyde reacts with ammonia (NH₃) to form an imine intermediate. Then, hydrogen cyanide (HCN) adds to the imine to produce an α-aminonitrile intermediate. The reaction can be represented as: .
Hydrolyze the α-aminonitrile: The α-aminonitrile is then hydrolyzed under acidic conditions (e.g., H₃O⁺) to convert the nitrile group (-CN) into a carboxylic acid (-COOH). This step produces phenylalanine. The reaction can be represented as: .
Verify the stereochemistry: Strecker synthesis typically produces a racemic mixture of the amino acid (both D- and L-forms). If a specific enantiomer of phenylalanine is required, additional steps such as chiral resolution or asymmetric synthesis may be necessary.
Summarize the overall process: The Strecker synthesis of phenylalanine involves starting with benzaldehyde, reacting it with ammonia and hydrogen cyanide to form an α-aminonitrile, and then hydrolyzing the nitrile group to yield phenylalanine.
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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 hydrogen cyanide. This process involves the formation of an α-amino nitrile intermediate, which can be hydrolyzed to yield the corresponding amino acid. Understanding this reaction is crucial for constructing amino acids like phenylalanine from simpler organic compounds.
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Synthesis of Amino Acids: Strecker Synthesis Concept 1
Amino Acids
Amino acids are organic compounds that serve as the building blocks of proteins. Each amino acid contains an amino group, a carboxyl group, and a distinctive side chain (R group) that determines its properties. Phenylalanine, specifically, is an essential amino acid with a benzyl side chain, making it important for protein synthesis and various metabolic processes.
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Functional Groups
Functional groups are specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules. In the context of Strecker synthesis, the aldehyde, amino, and nitrile groups play critical roles in the formation of phenylalanine. Recognizing how these functional groups interact is essential for predicting the outcomes of organic reactions.
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Related Practice
Textbook Question
Propose a mechanism for each step in the synthesis in part (a).
Textbook Question
Draw the electrophoretic separation of Trp, Cys, and His at pH 6.0.
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Textbook Question
Show how you would use bromination followed by amination to synthesize the following amino acids.
(b) leucine
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Textbook Question
Show how the following amino acids might be formed in the laboratory by reductive amination of the appropriate α-ketoacid.
(a) alanine
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Textbook Question
Propose a mechanism for each step in the synthesis in part (a).
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