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 24f

Chapter 5, Problem 24f

Prioritize the substituents at each chiral center and then, by comparing them to the models you created in Section 6.3.2, label the absolute configuration as R or S
(f)

Verified step by step guidance

Step 1: Identify the chiral center in the molecule. A chiral center is a carbon atom bonded to four different substituents. In the given structure, the carbon atom bonded to the hydroxyl group (OH), the oxygen atom in the ring, the ring itself, and the wedge/dash bond is the chiral center.

Step 2: Assign priorities to the substituents attached to the chiral center based on the Cahn-Ingold-Prelog (CIP) priority rules. These rules state that the substituent with the highest atomic number gets the highest priority. For this molecule: (1) The oxygen atom in the ring has the highest priority, (2) The hydroxyl group (OH) is next, (3) The ring structure is third, and (4) The hydrogen atom (not shown explicitly but implied by the dash bond) has the lowest priority.

Step 3: Orient the molecule so that the lowest priority group (hydrogen) is pointing away from you (on the dashed bond). This orientation is crucial for determining the absolute configuration.

Step 4: Trace the path from the highest priority substituent (1) to the second (2) and then to the third (3). If the path is clockwise, the configuration is R. If the path is counterclockwise, the configuration is S.

Step 5: Compare the result of your analysis to the models and examples provided in Section 6.3.2 to confirm the absolute configuration as R or S.

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Key Concepts

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

Chirality

Chirality refers to the geometric property of a molecule that makes it non-superimposable on its mirror image, much like left and right hands. Chiral centers, typically carbon atoms bonded to four different substituents, are crucial in determining the molecule's stereochemistry. Understanding chirality is essential for labeling configurations as R or S.

Cahn-Ingold-Prelog Priority Rules

The Cahn-Ingold-Prelog (CIP) priority rules are a set of guidelines used to assign priority to substituents attached to a chiral center. According to these rules, substituents are ranked based on the atomic number of the atoms directly attached to the chiral center, with higher atomic numbers receiving higher priority. This ranking is fundamental for determining the absolute configuration of chiral centers.

R and S Configuration

The R and S configuration system is used to describe the spatial arrangement of substituents around a chiral center. After assigning priorities to the substituents, the configuration is determined by observing the orientation of the highest priority substituent when the lowest priority is oriented away from the viewer. If the sequence of priorities is clockwise, the configuration is labeled as R (rectus), and if counterclockwise, it is labeled as S (sinister).

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R and S Naming- Step 4

Related Practice

Textbook Question

Prioritize the substituents at each chiral center and then, by comparing them to the models you created in Section 6.3.2, label the absolute configuration as R or S.

(d)

views

Textbook Question

Prioritize the substituents at each chiral center and then, by each of the two methods discussed in Section 6.3.2.4, determine the absolute configuration. [Do not use your models, except to check your answers.]

(d)

Textbook Question

Prioritize the substituents at each chiral center and then, by comparing them to the models you created in Section 6.3.2, label the absolute configuration as R or S.

(a)

Textbook Question

Of the following pairs, identify the higher priority substituent according to the CIP rules. (R = position of attachment to the asymmetric center.)

(a)

(h)

(c)