What is the configuration of each of the asymmetric centers in the following compounds?
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Verified step by step guidance

1. Step 1: Identify the asymmetric centers in each compound. An asymmetric center is a carbon atom bonded to four different groups. In compound A, the central carbon is bonded to H, CH3, Cl, and CHO. In compound B, the second and third carbons from the top are asymmetric centers.
2. Step 2: Assign priorities to the substituents attached to each asymmetric center based on the Cahn-Ingold-Prelog (CIP) priority rules. Higher atomic numbers take precedence, and if two atoms are the same, consider the atoms directly bonded to them.
3. Step 3: Determine the spatial arrangement of the substituents around each asymmetric center. Visualize or use a model to determine the order of substituents in a clockwise or counterclockwise direction.
4. Step 4: Assign the configuration as R or S for each asymmetric center. If the substituents decrease in priority in a clockwise direction, the configuration is R. If counterclockwise, the configuration is S. Ensure the lowest priority group is oriented away from you.
5. Step 5: Repeat the process for each asymmetric center in both compounds. For compound A, analyze the single asymmetric center. For compound B, analyze the two asymmetric centers separately.

Key Concepts

Chirality

Chirality refers to the geometric property of a molecule that makes it non-superimposable on its mirror image. Molecules with chirality typically contain one or more asymmetric centers, usually carbon atoms bonded to four different substituents. This property is crucial in organic chemistry as chiral molecules can exhibit different biological activities and properties.

Fischer Projections

Fischer projections are a two-dimensional representation of three-dimensional organic molecules, particularly useful for depicting the stereochemistry of chiral centers. In these projections, vertical lines represent bonds that go back into the plane, while horizontal lines represent bonds that come out of the plane. This format helps in visualizing the configuration (R or S) of asymmetric centers in a compound.

R and S Configuration

The R and S nomenclature is a system used to describe the absolute configuration of chiral centers in molecules. To assign R (rectus) or S (sinister) configuration, one must prioritize the substituents attached to the chiral carbon based on atomic number. The orientation of the molecule is then analyzed to determine whether the highest priority substituents are arranged in a clockwise (R) or counterclockwise (S) direction.