The relative configurations of the stereoisomers of tartaric acid were established by the following syntheses: (1) D-(+)-glyceraldehyde (with HCN) --> diastereomers A and B (separated) (2) Hydrolysis of A and B using aqueous Ba(OH)2 gave C and D, respectively. (3) HNO3 oxidation of C and D gave (-)-tartaric acid and meso-tartaric acid, respectively. (a) You know the absolute configuration of D-(+)-glyceraldehyde. Use Fischer projections to show the absolute configurations of products A, B, C, and D. (b) Show the absolute configurations of the three stereoisomers of tartaric acid: (+)-tartaric acid, (-)-tartaric acid, and meso-tartaric acid.

Verified step by step guidance

1. <insert step 1> Start by recalling the absolute configuration of D-(+)-glyceraldehyde, which is known to be (R). Draw its Fischer projection with the hydroxyl group on the right side.
2. <insert step 2> Consider the reaction of D-(+)-glyceraldehyde with HCN, which adds a cyanohydrin group, creating a new chiral center. This results in two diastereomers, A and B. Draw the Fischer projections for both, considering the possible configurations (R/S) at the new chiral center.
3. <insert step 3> Perform hydrolysis of A and B using aqueous Ba(OH)2. This step converts the cyanohydrin group into a carboxylic acid group, forming compounds C and D. Draw the Fischer projections for C and D, maintaining the configurations from the previous step.
4. <insert step 4> Oxidize C and D using HNO3. This step will convert the aldehyde group into a carboxylic acid group, resulting in tartaric acid stereoisomers. Draw the Fischer projections for the resulting (-)-tartaric acid and meso-tartaric acid, considering the stereochemistry from the previous step.
5. <insert step 5> Finally, draw the Fischer projections for the three stereoisomers of tartaric acid: (+)-tartaric acid, (-)-tartaric acid, and meso-tartaric acid. Assign the absolute configurations (R/S) to each chiral center in these molecules.>

Key Concepts

Stereochemistry

Stereochemistry is the study of the spatial arrangement of atoms in molecules and how this affects their chemical behavior. It includes concepts such as chirality, where molecules can exist as non-superimposable mirror images (enantiomers), and diastereomers, which are stereoisomers that are not mirror images. Understanding stereochemistry is crucial for analyzing the configurations of compounds like tartaric acid and its derivatives.

Fischer Projections

Fischer projections are a two-dimensional representation of three-dimensional organic molecules, particularly useful for depicting the stereochemistry of carbohydrates and amino acids. In a Fischer projection, vertical lines represent bonds that go back into the plane, while horizontal lines represent bonds that come out of the plane. This method allows for easy visualization of the absolute configurations of chiral centers, which is essential for solving the question regarding the stereoisomers of tartaric acid.

Oxidation and Hydrolysis Reactions

Oxidation and hydrolysis are fundamental chemical reactions that involve the transformation of organic compounds. Oxidation typically involves the addition of oxygen or the removal of hydrogen, while hydrolysis involves the reaction of a compound with water, leading to the breakdown of that compound. In the context of the question, understanding these reactions is vital for tracing the synthesis of tartaric acid from its precursors and determining the configurations of the resulting products.