Which of the following is not a correct perspective representation of a stereoisomer of 2,3-dibromobutane?
A.
B.
C.
D.
Answer (2)
Structure A is a meso compound (2R,3S) or (2S,3R).
Structures B and C are enantiomers, representing either (2R,3R) or (2S,3S).
Structure D has incorrect connectivity; the bromine atoms are attached to the methyl groups.
Therefore, structure D is not a correct representation of 2,3-dibromobutane, and the answer is D .
Explanation
Understanding the Problem The question asks us to identify which of the given perspective representations (A, B, C, D) is NOT a correct stereoisomer of 2,3-dibromobutane. To do this, we need to analyze each structure and determine its stereochemical configuration.
Analyzing Each Structure Let's analyze each structure:
Structure A: H&C H
Br H3C CIC-H Br HC-C-Br Br C-CH H
H CH3
This appears to be a meso compound, where the two chiral centers have opposite configurations (one R, one S). Specifically, it's (2R,3S) or (2S,3R), which are equivalent due to the internal plane of symmetry.
Structure B: Br CH3 Br C-CH CH3
This structure represents a stereoisomer where both chiral centers have the same configuration. It could be either (2R,3R) or (2S,3S).
Structure C: Br CH3 Br C-CH CH3
Similar to structure B, this also represents a stereoisomer where both chiral centers have the same configuration. It could be either (2R,3R) or (2S,3S). However, it is the enantiomer of structure B.
Structure D: H3C Br H3C H
This structure seems incorrect. The central carbon atoms do not have the correct connectivity to the bromine atoms. It looks like the bromine atoms are attached to the methyl groups, which is not 2,3-dibromobutane.
Identifying the Incorrect Representation Based on the analysis, structure D is not a correct representation of 2,3-dibromobutane or any of its stereoisomers because the bromine atoms are incorrectly attached to the methyl groups instead of the second and third carbon atoms in the butane chain.
Conclusion Therefore, the answer is D.
Examples
Understanding stereoisomers is crucial in drug design. Many drugs are chiral, and their different stereoisomers can have vastly different effects on the body. For example, one stereoisomer might be effective at treating a disease, while another might be toxic. Identifying incorrect stereoisomer representations helps ensure that the correct drug is synthesized and administered, preventing potential harm to patients.
Structure D is not a correct representation of a stereoisomer of 2,3-dibromobutane due to incorrect connectivity of bromine atoms. Structures A, B, and C represent valid stereoisomers. Therefore, the answer is D.
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