Ch. 6 - Stereoisomerism: Arrangement of Atoms in Space

Mullins - Organic Chemistry: A Learner Centered Approach 1st Edition

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Mullins 1st Edition

Ch. 6 - Stereoisomerism: Arrangement of Atoms in Space

Problem 51e

Chapter 5, Problem 51e

Assign the absolute stereochemistry for each of the following molecules.
(e)

Verified step by step guidance

Step 1: Identify the stereocenter in the molecule. The stereocenter is the carbon atom bonded to four different groups: the amino group (NH₂), the carboxylic acid group (CO₂H), the hydrogen atom (H), and the phenyl group (C₆H₅).

Step 2: Assign priorities to the substituents attached to the stereocenter based on the Cahn-Ingold-Prelog (CIP) priority rules. The priority is determined by atomic number: (1) CO₂H (highest priority due to oxygen), (2) NH₂, (3) C₆H₅, and (4) H (lowest priority).

Step 3: Orient the molecule so that the lowest priority group (H) is pointing away from you. This is typically represented as a dashed wedge in the diagram.

Step 4: Determine the order of the remaining three groups (CO₂H, NH₂, and C₆H₅) as you move clockwise or counterclockwise. Trace the path from the highest priority group (CO₂H) to the second (NH₂) and then to the third (C₆H₅).

Step 5: Assign the absolute configuration based on the direction of the path. If the path is clockwise, the configuration is R. If the path is counterclockwise, the configuration is S.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Stereochemistry

Stereochemistry is the study of the spatial arrangement of atoms in molecules and how this affects their chemical behavior. It is crucial for understanding isomers, particularly enantiomers, which are non-superimposable mirror images of each other. In organic chemistry, stereochemistry is often denoted using the R/S system, which helps in assigning absolute configurations to chiral centers.

Chirality

Chirality refers to the property of a molecule that makes it non-superimposable on its mirror image, much like left and right hands. A chiral molecule typically has one or more chiral centers, usually carbon atoms bonded to four different substituents. Identifying chirality is essential for assigning stereochemistry, as it determines the molecule's optical activity and interactions in biological systems.

Cahn-Ingold-Prelog Priority Rules

The Cahn-Ingold-Prelog (CIP) priority rules are a set of guidelines used to assign priorities to substituents attached to a chiral center based on atomic number and connectivity. The highest priority is given to the atom with the highest atomic number directly attached to the chiral center. These rules are fundamental for determining the R or S configuration of chiral molecules, which is necessary for accurately describing their stereochemistry.

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Related Practice

Textbook Question

Assign the absolute stereochemistry for each of the following molecules drawn in their Fischer projection.

(a)

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Textbook Question

Assign the absolute stereochemistry for each of the following molecules drawn in their Fischer projection.

(d)

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Textbook Question

Define the relationship between each set of two molecules as chain isomers, positional isomers, functional group isomers, enantiomers, diastereomers, conformational isomers, or identical

(h)

817

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Textbook Question

Complete the structure of each of these so that it matches the (R) or (S) configuration associated with the name.

(d)

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Textbook Question

Complete the structure of each of these so that it matches the (R) or (S) configuration associated with the name.

(a)

1141