Esterase is an enzyme that catalyzes the hydrolysis of esters. It hydrolyzes esters of l-amino acids more rapidly than esters of D-amino acids. How can this enzyme be used to separate a racemic mixture of amino acids?
Ch. 21 - Amino Acids, Peptides, and Proteins
Chapter 22, Problem 23b
What alkyl halide is used in the acetamidomalonic ester synthesis to prepare
b. phenylalanine?
Verified step by step guidance1
Understand the acetamidomalonic ester synthesis: This is a method used to synthesize α-amino acids. It involves the alkylation of the acetamidomalonic ester, followed by hydrolysis and decarboxylation.
Identify the target amino acid: Phenylalanine is an α-amino acid with a benzyl side chain (C6H5-CH2-). This means the alkyl halide used must introduce this benzyl group.
Determine the structure of the required alkyl halide: To introduce the benzyl group, the alkyl halide should be benzyl bromide (C6H5-CH2-Br) or benzyl chloride (C6H5-CH2-Cl). These are common alkyl halides used for this purpose.
Outline the reaction mechanism: The acetamidomalonic ester undergoes deprotonation at the α-carbon (between the two ester groups) using a strong base, forming a carbanion. This carbanion then performs an SN2 nucleophilic substitution on the alkyl halide, replacing the halide group with the benzyl group.
Conclude the synthesis: After the alkylation step, the product undergoes hydrolysis to remove the ester groups and the amide group, followed by decarboxylation to yield phenylalanine.

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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Acetamidomalonic Ester Synthesis
Acetamidomalonic ester synthesis is a method used to create amino acids, particularly phenylalanine. This reaction involves the use of acetamidomalonic ester, which undergoes alkylation to introduce an alkyl group, followed by hydrolysis and decarboxylation to yield the desired amino acid. Understanding this synthesis is crucial for identifying the specific alkyl halide needed for the reaction.
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Synthesis of Amino Acids: Acetamidomalonic Ester Synthesis Example 2
Alkyl Halides
Alkyl halides are organic compounds containing a carbon atom bonded to a halogen atom (such as chlorine, bromine, or iodine). They serve as key reactants in various organic reactions, including nucleophilic substitutions. In the context of acetamidomalonic ester synthesis, the choice of alkyl halide affects the structure of the resulting amino acid, making it essential to select the correct one for phenylalanine production.
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Nucleophilic Substitution Reactions
Nucleophilic substitution reactions are fundamental processes in organic chemistry where a nucleophile replaces a leaving group in a molecule. In the synthesis of phenylalanine, the nucleophile (the acetamidomalonic ester) attacks the carbon atom of the alkyl halide, leading to the formation of a new carbon-carbon bond. Understanding the mechanisms and types of nucleophilic substitutions is vital for predicting the outcomes of the synthesis.
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Nucleophiles and Electrophiles can react in Substitution Reactions.
Related Practice
Textbook Question
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Textbook Question
What alkyl halide is used in the acetamidomalonic ester synthesis to prepare
a. lysine?
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Textbook Question
What amino acid is formed using the N-phthalimidomalonic ester synthesis when the following alkyl halides are used in the third step?
b. CH3SCH2CH2Br
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Textbook Question
What amino acid is formed using the N-phthalimidomalonic ester synthesis when the following alkyl halides are used in the third step?
a.
Textbook Question
Draw the tetrapeptide Ala-Thr-Asp-Asn and indicate the peptide bonds.
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Textbook Question
What amino acid is formed when the aldehyde used in the Strecker synthesis is
b. 2-methylbutanal?
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