Which of the following structures are perspective formulas of the stereoisomers of 2,3-dibromobutane?
a. C
b. D
c. E
d. B
e. A
Answer (2)
Stereoisomers of 2,3-dibromobutane include enantiomeric pairs and a meso compound.
Analyze each given structure to determine if it represents a valid stereoisomer of 2,3-dibromobutane.
Structure A represents one of the enantiomers.
Structure E represents the meso compound. Therefore, the answer is A and E.
Explanation
Understanding the Problem The question asks us to identify which of the given structures (A, B, C, D, E) represent stereoisomers of 2,3-dibromobutane. Stereoisomers have the same molecular formula and connectivity but differ in the spatial arrangement of atoms. 2,3-dibromobutane has two chiral centers (carbons 2 and 3), leading to stereoisomers.
Identifying Stereoisomers Let's analyze the possible stereoisomers. Carbons 2 and 3 can each have R or S configuration. So, we can have (2R,3R), (2S,3S), (2R,3S), and (2S,3R). The (2R,3S) and (2S,3R) forms are actually the same meso compound due to internal symmetry. Therefore, we have three stereoisomers: (2R,3R), (2S,3S) and the meso compound.
Analyzing the Given Structures Now, let's examine the given structures:
A: Has the structure where on C2, C H 3 is on top and Br is on the bottom, and on C3, Br is on top and C H 3 is on the bottom. This could be one of the enantiomers (e.g., 2R,3R).
B: Has the structure where on C2, C H 3 is on top and Br is on the bottom, and on C3, Br is on top and C H 3 is on the bottom. This is the same as A, just rotated. So, A and B are the same enantiomer.
C: Has the structure where on C2, C H 3 is on top and H is on the bottom, and on C3, Br is on top and C H 3 is on the bottom. This is NOT 2,3-dibromobutane since C2 has a hydrogen instead of a bromine.
D: Has the structure where on C2, H is on top and C H 3 is on the bottom, and on C3, Br is on top and C H 3 is on the bottom. This is NOT 2,3-dibromobutane since C2 has a hydrogen instead of a bromine.
E: Has the structure where on C2, Br is on top and C H 3 is on the bottom, and on C3, Br is on top and C H 3 is on the bottom. This represents the meso compound (2R,3S or 2S,3R).
Identifying Correct Options From the analysis, structure A (and B, which is the same) represents one enantiomer (either 2R,3R or 2S,3S), and structure E represents the meso compound. Therefore, A and E are perspective formulas of stereoisomers of 2,3-dibromobutane.
Final Answer The correct options are A and E.
Examples
Understanding stereoisomers is crucial in drug design. Many drugs are chiral, and their different stereoisomers can have drastically different effects on the body. For example, one stereoisomer might be effective at treating a disease, while another might be toxic. Identifying and synthesizing the correct stereoisomer is therefore essential for creating safe and effective medications. This problem helps to visualize and differentiate between different stereoisomers, which is a fundamental skill in organic chemistry and pharmacology.
The perspective formulas of the stereoisomers of 2,3-dibromobutane include structures A (and B) as the enantiomers and structure E as the meso compound. Therefore, the correct answers are A and E.
;
