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
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5. Chirality
R and S Configuration
5:17 minutesProblem 54
Textbook Question
Chloramphenicol is a broad-spectrum antibiotic that is particularly useful against typhoid fever. What is the configuration of each of its asymmetric centers?
Verified step by step guidance1
Step 1: Identify the asymmetric centers in the chloramphenicol molecule. An asymmetric center is a carbon atom bonded to four different groups. In the given structure, there are two asymmetric centers: the first carbon bonded to HO, H, a benzene ring, and another carbon; and the second carbon bonded to CH2OH, H, NH group, and the first carbon.
Step 2: Assign priorities to the substituents attached to each asymmetric center based on the Cahn-Ingold-Prelog (CIP) priority rules. These rules state that the atom with the highest atomic number gets the highest priority. For the first asymmetric center, the groups are HO, H, benzene ring, and the adjacent carbon. For the second asymmetric center, the groups are CH2OH, H, NH group, and the adjacent carbon.
Step 3: Determine the spatial arrangement of the substituents around each asymmetric center. Visualize the molecule in 3D or use the wedge and dash notation provided in the structure. The wedge represents a bond coming out of the plane, and the dash represents a bond going into the plane.
Step 4: Assign the configuration (R or S) to each asymmetric center. To do this, orient the molecule so that the lowest priority group (usually H) is pointing away from you. Then, trace the path from the highest priority group to the second and third priority groups. If the path is clockwise, the configuration is R; if counterclockwise, it is S.
Step 5: Repeat the process for both asymmetric centers and confirm the configurations. For the first asymmetric center, analyze the arrangement of HO, H, benzene ring, and adjacent carbon. For the second asymmetric center, analyze the arrangement of CH2OH, H, NH group, and adjacent carbon.
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Video duration:
5mKey Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Asymmetric Centers
Asymmetric centers, or chiral centers, are carbon atoms bonded to four different substituents, leading to non-superimposable mirror images known as enantiomers. The configuration of these centers is crucial in determining the optical activity and biological properties of molecules, such as antibiotics like chloramphenicol.
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Stereochemistry
Stereochemistry is the study of the spatial arrangement of atoms in molecules and how this affects their chemical behavior. Understanding stereochemistry is essential for determining the configuration of asymmetric centers, which can influence the efficacy and mechanism of action of compounds like chloramphenicol.
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CIP Priority Rules
CIP (Cahn-Ingold-Prelog) priority rules are a set of guidelines used to assign priorities to the substituents attached to an asymmetric center based on atomic number and connectivity. These rules help in determining the R or S configuration of chiral centers, which is vital for accurately describing the structure of chloramphenicol.
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