Which of the following statements accurately describes the stereochemical outcome of the Strecker synthesis of alanine?

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11ecba2d_1280_fb54_a3bf_af5eb919e3f4_MD0008_00 The Strecker synthesis is used to make α-amino acids from an aldehyde using ammonium chloride (NH₄Cl) and potassium cyanide (KCN). The first step of the reaction proceeds with protonation of the carbonyl oxygen by ammonium (NH₄⁺), followed by nucleophilic attack of the carbonyl carbon by ammonia (NH₃), resulting in dehydration and imine formation. In the second step, a cyanide anion is added to the imine to form an aminonitrile. Finally, in the third step, the nitrile (R-CN) nitrogen is protonated, and two water molecules add to the nitrile carbon in succession, eliminating ammonia from the nitrile and forming the carboxylic acid of the α-amino acid. Alanine can be synthesized via the Strecker synthesis from acetaldehyde, NH₄Cl, and KCN. Acetaldehyde does not have a stereocenter, and the imine intermediate also does not have a stereocenter and is a planar molecule, allowing nucleophilic attack to occur from either above or below the plane. Therefore, the reaction is not stereospecific and the product will be a mixture of L- and D-alanine. The same outcome is obtained for amino acids produced by the Gabriel synthesis because the final step (decarboxylation) is not stereospecific. (Choices A and B) Because the reaction proceeds through the formation of a planar intermediate, the product will be a mixture of L- and D-amino acids rather than just one or the other. (Choice D) The α-carbon of alanine, as well as all amino acids except glycine, contains four different substituents, making it a stereocenter. Educational objective: The Strecker synthesis is used to generate α-amino acids from an aldehyde using ammonium chloride (NH₄Cl) and potassium cyanide (KCN). Because the imine intermediate formed during the reaction is planar (no stereocenters), nucleophilic addition can occur from either above or below the plane. Therefore, the Strecker synthesis is not a stereospecific reaction and produces a mixture of L- and D-amino acids.

Which of the Following Statements Accurately Describes the Stereochemical Outcome