Textbook Question
Star (*) each asymmetric carbon atom in the following examples, and determine whether it has the (R) or (S) configuration.
(i)
5. Chirality
R and S Configuration
5:32 minutesProblem 30a,b
Textbook Question
What is the configuration of the following compounds? (Use the given structures to answer the question.)
a. ()-glyceric acid
b. ()-isoserine
Verified step by step guidance1
Step 1: Identify the chiral center in each compound. Both (-)-glyceric acid and (+)-isoserine have one chiral center, which is the carbon atom bonded to four different groups.
Step 2: Assign priorities to the substituents attached to the chiral center based on the Cahn-Ingold-Prelog priority rules. For (-)-glyceric acid, the groups are COOH, CH2OH, H, and OH. For (+)-isoserine, the groups are COOH, CH2NH3+, H, and OH.
Step 3: Orient the molecule so that the lowest priority group (H) is pointing away from you (on the dashed wedge). This allows you to determine the configuration by tracing the path of the remaining groups in order of priority.
Step 4: 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 the path is counterclockwise, the configuration is S.
Step 5: Use the given labels (-) and (+) to confirm the optical activity of the compounds. (-)-glyceric acid is levorotatory, and (+)-isoserine is dextrorotatory. This does not affect the R/S configuration but provides additional information about the compounds.
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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 the configuration of compounds, particularly in organic chemistry, where the three-dimensional orientation of atoms can lead to different isomers with distinct properties.
Chirality
Chirality refers to the property of a molecule that makes it non-superimposable on its mirror image, much like left and right hands. Chiral molecules often have one or more stereocenters, which are carbon atoms bonded to four different substituents, leading to different configurations known as enantiomers. Understanding chirality is essential for determining the configuration of compounds.
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 stereocenter in order to determine the configuration of chiral centers. By evaluating the atomic number and connectivity of the substituents, chemists can classify the configuration as either R (rectus) or S (sinister), which is vital for accurately describing the stereochemistry of organic compounds.
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