What amino acid is formed using the N-phthalimidomalonic ester synthesis when the following alkyl halides are used in the third step?
b. CH₃SCH₂CH₂Br

Verified step by step guidance

Step 1: Understand the N-phthalimidomalonic ester synthesis. This method is used to synthesize amino acids by introducing an alkyl group into the malonic ester derivative. The process involves three main steps: (1) formation of the N-phthalimidomalonic ester, (2) alkylation using an alkyl halide, and (3) hydrolysis and decarboxylation to yield the amino acid.

Step 2: Analyze the alkyl halide provided, CH3SCH2CH2Br. This molecule contains a sulfur atom in the form of a thioether (-CH3S-) attached to a two-carbon chain ending in a bromine atom. The bromine atom is the leaving group, which will be replaced during the alkylation step.

Step 3: In the alkylation step, the N-phthalimidomalonic ester undergoes nucleophilic substitution. The carbanion generated from the malonic ester attacks the electrophilic carbon attached to the bromine in CH3SCH2CH2Br, resulting in the addition of the -CH3SCH2CH2- group to the malonic ester.

Step 4: After alkylation, the product undergoes hydrolysis to remove the phthalimide group and decarboxylation to eliminate one of the carboxyl groups. This transforms the intermediate into an amino acid with the structure: H2N-CH(CH3SCH2CH2)-COOH.

Step 5: Recognize the amino acid formed. The structure H2N-CH(CH3SCH2CH2)-COOH corresponds to methionine, an amino acid with a thioether functional group in its side chain. Thus, the synthesis yields methionine as the final product.

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Key Concepts

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

N-phthalimidomalonic ester synthesis

N-phthalimidomalonic ester synthesis is a method for synthesizing amino acids that involves the reaction of phthalimide with malonic ester. This process typically includes the formation of a phthalimide derivative, followed by alkylation with an alkyl halide, and subsequent hydrolysis to yield the corresponding amino acid. The reaction is notable for its ability to introduce a side chain into the amino acid structure.

Alkyl halides

Alkyl halides are organic compounds containing a carbon chain bonded to a halogen atom (such as bromine, chlorine, or iodine). In the context of the N-phthalimidomalonic ester synthesis, alkyl halides serve as the electrophilic agents that react with the nucleophilic malonic ester derivative. The choice of alkyl halide influences the structure of the resulting amino acid, as it determines the side chain attached to the alpha carbon.

Amino acid structure

Amino acids are organic molecules that serve as the building blocks of proteins. Each amino acid has a central carbon atom bonded to an amino group, a carboxyl group, a hydrogen atom, and a variable side chain (R group) that defines its unique properties. The specific amino acid formed in the N-phthalimidomalonic ester synthesis depends on the alkyl halide used, which contributes to the side chain of the final product.

What amino acid is formed using the N-phthalimidomalonic ester synthesis when the following alkyl halides are used in the third step? b. CH3SCH2CH2Br