For each structure,
1. draw all the stereoisomers.
2. label each structure as chiral or achiral.
3. give the relationships between the stereoisomers (enantiomers, diastereomers).
(a)

Verified step by step guidance

1. Step 1: Analyze the given structure. The molecule is a Fischer projection with an aldehyde group (CHO) at the top, two hydroxyl groups (OH) on the horizontal bonds, and a primary alcohol group (CH2OH) at the bottom. The central carbons are stereocenters.
2. Step 2: Determine the stereoisomers. Each stereocenter can have two configurations (R or S). For two stereocenters, the total number of stereoisomers is 2^n, where n is the number of stereocenters. Here, n = 2, so there are 4 stereoisomers.
3. Step 3: Draw all stereoisomers. To do this, assign different combinations of R and S configurations to the two stereocenters. For example, (R,R), (R,S), (S,R), and (S,S). Represent each configuration using Fischer projections.
4. Step 4: Label each structure as chiral or achiral. A molecule is chiral if it has a non-superimposable mirror image. Check for symmetry in each stereoisomer to determine chirality.
5. Step 5: Determine the relationships between the stereoisomers. Compare each pair of stereoisomers. If they are non-superimposable mirror images, they are enantiomers. If they are not mirror images but differ in configuration, they are diastereomers.

Key Concepts

Stereoisomerism

Stereoisomerism refers to the phenomenon where compounds have the same molecular formula and connectivity of atoms but differ in the spatial arrangement of their atoms. This can lead to different physical and chemical properties. The two main types of stereoisomers are enantiomers, which are non-superimposable mirror images, and diastereomers, which are not mirror images of each other.

Chirality

Chirality is a property of a molecule that makes it non-superimposable on its mirror image, much like left and right hands. A chiral molecule typically has at least one carbon atom bonded to four different substituents, creating two distinct forms (enantiomers). In contrast, achiral molecules can be superimposed on their mirror images and do not exhibit this property.

Relationship between Stereoisomers

The relationship between stereoisomers is crucial for understanding their interactions and properties. Enantiomers have identical physical properties except for their interaction with polarized light and reactions in chiral environments. Diastereomers, on the other hand, differ in physical properties and reactivity, making their relationships more complex. Identifying these relationships helps in predicting the behavior of compounds in various chemical contexts.