Textbook Question
What type of isomerism is indicated by each of the following pairs of molecules? Be as specific as possible.
(d)
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5. Chirality
What is the Relationship Between Isomers?
3:10 minutesProblem 19
Textbook Question
Do the following structures represent identical compounds or a pair of enantiomers?
Verified step by step guidance1
Step 1: Analyze the two structures provided. Both structures are tetrahedral molecules with a central carbon atom bonded to four different groups: CH₃, CH₂CH₃, CH=CH₂, and H. This makes the central carbon a chiral center.
Step 2: Determine the spatial arrangement of the substituents around the chiral center. Pay attention to the wedge and dash bonds, which indicate the three-dimensional orientation of the groups.
Step 3: Compare the substituent positions in the two structures. In the first structure, CH₃ is on the wedge bond, H is on the dash bond, CH₂CH₃ is in the plane, and CH=CH₂ is also in the plane. In the second structure, CH₃ is on the wedge bond, H is on the dash bond, but CH₂CH₃ and CH=CH₂ have swapped positions in the plane.
Step 4: Recall the definition of enantiomers. Enantiomers are non-superimposable mirror images of each other, meaning they have opposite configurations at the chiral center. Identical compounds, on the other hand, have the same configuration at the chiral center.
Step 5: Based on the analysis, determine whether the two structures are identical or enantiomers. Since the substituents are arranged differently in the plane, the two structures represent a pair of enantiomers.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Stereoisomerism
Stereoisomerism refers to the phenomenon where compounds have the same molecular formula and connectivity of atoms but differ in the spatial arrangement of those atoms. This can lead to different physical and chemical properties. Stereoisomers can be further classified into geometric isomers (cis/trans) and optical isomers (enantiomers). Understanding stereoisomerism is crucial for determining whether two structures are identical or represent enantiomers.
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Enantiomers
Enantiomers are a specific type of stereoisomer that are non-superimposable mirror images of each other. They typically arise in molecules that contain a chiral center, which is a carbon atom bonded to four different substituents. Enantiomers have identical physical properties in an achiral environment but can exhibit different behaviors in chiral environments, such as biological systems. Identifying enantiomers is essential for understanding the question of whether the given structures are identical or not.
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Chirality
Chirality is a property of a molecule that makes it non-superimposable on its mirror image, much like how left and right hands are mirror images but cannot be perfectly aligned. A chiral molecule typically has at least one chiral center, often a carbon atom with four different substituents. The presence of chirality is a key factor in determining whether two structures are enantiomers, as only chiral molecules can exist as pairs of enantiomers.
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