Indicate whether each pair of Fischer projections represents enantiomers or identical structures.
a.

Verified step by step guidance

1. Step 1: Recall the definition of enantiomers. Enantiomers are non-superimposable mirror images of each other, meaning they have the same connectivity but opposite configurations at all chiral centers.
2. Step 2: Analyze the Fischer projections provided in the problem. Identify the chiral centers in each structure and note the arrangement of substituents around these centers.
3. Step 3: Compare the configurations of the chiral centers in the two Fischer projections. For each chiral center, determine whether the substituents are arranged in the same way or in opposite configurations (R vs. S).
4. Step 4: If all chiral centers have opposite configurations, the structures are enantiomers. If all chiral centers have the same configuration, the structures are identical.
5. Step 5: Conclude whether the given Fischer projections represent enantiomers or identical structures based on your comparison of the chiral centers.

Key Concepts

Fischer Projections

Fischer projections are a two-dimensional representation of three-dimensional organic molecules, particularly useful for depicting stereochemistry. In these diagrams, vertical lines represent bonds that project away from the viewer, while horizontal lines represent bonds that project towards the viewer. This format is especially helpful for visualizing the spatial arrangement of substituents around chiral centers.

Enantiomers

Enantiomers are a type of stereoisomer that are non-superimposable mirror images of each other. They typically arise from molecules that contain one or more chiral centers, leading to distinct spatial arrangements of atoms. Enantiomers have identical physical properties in an achiral environment but can exhibit different behaviors in chiral environments, such as biological systems.

Identical Structures

Identical structures refer to molecules that have the same molecular formula and connectivity of atoms, resulting in the same spatial arrangement. Unlike enantiomers, identical structures can be superimposed on one another, meaning they are indistinguishable in all respects. Recognizing identical structures is crucial in stereochemistry to differentiate them from stereoisomers like enantiomers.