Question

In which of the following cases, the configuration of chiral carbon is retained in the product. (A) (B) (C) (D)

Short answer

After analyzing all the cases (A, B, C, D), the configuration of the chiral carbon is retained in the product in the case(s) _______.

Step-by-step solution

Case A:

Analyze the starting material and product structures in case A to determine the stereochemistry of the chiral carbon. Compare the configuration before and after the reaction. If the configuration remains the same (R to R or S to S), then the chiral carbon's configuration is retained in the product.

Case B:

Analyze the starting material and product structures in case B to determine the stereochemistry of the chiral carbon. Compare the configuration before and after the reaction. If the configuration remains the same (R to R or S to S), then the chiral carbon's configuration is retained in the product.

Case C:

Analyze the starting material and product structures in case C to determine the stereochemistry of the chiral carbon. Compare the configuration before and after the reaction. If the configuration remains the same (R to R or S to S), then the chiral carbon's configuration is retained in the product.

Case D:

Analyze the starting material and product structures in case D to determine the stereochemistry of the chiral carbon. Compare the configuration before and after the reaction. If the configuration remains the same (R to R or S to S), then the chiral carbon's configuration is retained in the product.

Final Answer:

After analyzing all the cases (A, B, C, D), identify which case(s) has the chiral carbon's configuration retained in the product. That case will be the answer to the question.

Key concepts

Chiral Carbon

The concept of a chiral carbon is fundamental in the study of stereochemistry. A chiral carbon atom, also known as a stereogenic center, is one that is bonded to four different atoms or groups. This unique arrangement allows for two non-superimposable mirror images, or enantiomers, to exist. These enantiomers can have drastically different effects in biological systems despite only differing in their three-dimensional orientation.
A simple visual analogy is to think of your hands. They are mirror images but cannot be perfectly aligned on top of each other, which is similar to how enantiomers behave.

• Key in recognizing chirality is the presence of four different groups attached to a carbon.
• Such a carbon will have two possible spatial arrangements, leading to the enantiomers known as R and S configurations.

Identifying chiral carbons in a molecule is the first step before determining the specific configuration, which can play a critical role in how substances react chemically and biologically.

Stereochemistry

Stereochemistry deals with the spatial arrangement of atoms within molecules, which is crucial for understanding the reactivity and interaction of molecules. In the context of organic chemistry, stereochemistry becomes important because the 3D arrangement of atoms influences how molecules interact with one another or within biological systems.
Key elements of stereochemistry include:

• Configurational Isomers: These are isomers that can only be interconverted by breaking and reforming bonds, which includes enantiomers like R and S.
• Conformational Isomers: These are isomers that can be interconverted by rotations around single bonds and do not involve breaking any bonds.

Understanding stereochemistry helps chemists predict product outcomes and design reactions. For example, determining whether a reaction retains the configuration of a chiral center in a molecule's product can be crucial for pharmaceuticals, where one enantiomer might be active and the other inactive or harmful.

R and S Configuration

The R and S configuration is a method used to describe the absolute configuration of chiral centers in molecules. It's like identifying the exact hand orientation in a handshake. To assign these configurations:

• Identify the chiral carbon and its four substituents.
• Assign priority to each substituent based on the atomic number; the higher the atomic number, the higher the priority.
• Arrange the molecule in space so the substituent with the lowest priority is oriented away from you.
• Trace a path from the highest priority substituent to the third highest. If the path is clockwise, it's an R (for Rectus) configuration; if counterclockwise, it's an S (for Sinister) configuration.

This systematic approach helps consistently label the stereochemistry of chiral centers and is critical when assessing if reactions retain the configuration of the original chiral carbon from the reactant to the product, as seen in the provided cases. Retention means the stereochemistry remains the same, such as R to R or S to S, which can impact the chemical properties and biological activity of the molecule.