Chapter 6: Problem 30
How many stereoisomers exist of 2,3-dibromobutane? A. 1 B. 2 C. 3 D. 4
Short Answer
Expert verified
3 stereoisomers
Step by step solution
01
Identify Chiral Centers
Examine the structure of 2,3-dibromobutane. Identify the two carbon atoms at positions 2 and 3. Both carbons have four different groups attached, making them chiral centers.
02
Determine the Maximum Number of Stereoisomers
Use the formula for calculating the number of stereoisomers for a molecule with n chiral centers, which is given by 2^n. Here, n=2, so the maximum number of stereoisomers is 2^2 = 4.
03
Consider Meso Compounds
Check if the molecule has any internal plane of symmetry, which could reduce the number of stereoisomers. For 2,3-dibromobutane, there is one meso compound that reduces the count.
04
Calculate the Final Number of Stereoisomers
Subtract the number of meso compounds from the total possible stereoisomers. Therefore, 4 - 1 = 3 stereoisomers exist for 2,3-dibromobutane.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
chiral centers
In stereochemistry, a chiral center is a carbon atom that has four different groups attached to it. This unique arrangement means the molecule can exist in two non-superimposable mirror images, known as enantiomers.
To identify chiral centers in 2,3-dibromobutane, look at the carbon atoms at positions 2 and 3. Each of these carbons is bonded to a hydrogen atom (H), a bromine atom (Br), a methyl group (CH3), and an ethyl group (C2H5).
Because all four groups attached to these carbons are different, these atoms are chiral centers. Recognizing these centers is key to understanding how the molecule can have different spatial arrangements. Chiral centers are the foundation for both stereoisomers and meso compounds.
To identify chiral centers in 2,3-dibromobutane, look at the carbon atoms at positions 2 and 3. Each of these carbons is bonded to a hydrogen atom (H), a bromine atom (Br), a methyl group (CH3), and an ethyl group (C2H5).
Because all four groups attached to these carbons are different, these atoms are chiral centers. Recognizing these centers is key to understanding how the molecule can have different spatial arrangements. Chiral centers are the foundation for both stereoisomers and meso compounds.
stereoisomers
Stereoisomers are molecules that have the same molecular formula and sequence of bonded atoms (constitution), but differ in the three-dimensional orientations of their atoms in space. For a molecule with chiral centers, the number of possible stereoisomers can be calculated using the formula 2n, where n is the number of chiral centers.
In the case of 2,3-dibromobutane, with two chiral centers, the maximum number of stereoisomers is 22 = 4. These stereoisomers include different combinations of spatial arrangements around each chiral center.
Stereoisomers are important because they can have drastically different properties, even though their chemical composition is the same. These properties include different physical characteristics like boiling points and melting points, as well as different biological activities. Understanding stereoisomers is crucial for fields ranging from chemistry to pharmacology.
In the case of 2,3-dibromobutane, with two chiral centers, the maximum number of stereoisomers is 22 = 4. These stereoisomers include different combinations of spatial arrangements around each chiral center.
Stereoisomers are important because they can have drastically different properties, even though their chemical composition is the same. These properties include different physical characteristics like boiling points and melting points, as well as different biological activities. Understanding stereoisomers is crucial for fields ranging from chemistry to pharmacology.
meso compounds
Meso compounds are a unique type of stereoisomer. They contain multiple chiral centers but do not exhibit chirality due to an internal plane of symmetry. This means that even though the molecule has chiral centers, the overall molecule is achiral because it can be divided into two symmetrical halves.
For 2,3-dibromobutane, one of the stereoisomers is a meso compound. This particular arrangement has an internal plane of symmetry, which reduces the overall number of stereoisomers. In the equation to find stereoisomers, we must subtract any meso compounds from the total calculated.
Therefore, for 2,3-dibromobutane, we calculate 4 possible stereoisomers (22) and then subtract the 1 meso compound, resulting in 3 unique stereoisomers. Understanding meso compounds helps clarify why not all theoretically possible stereoisomers are observed in practice.
For 2,3-dibromobutane, one of the stereoisomers is a meso compound. This particular arrangement has an internal plane of symmetry, which reduces the overall number of stereoisomers. In the equation to find stereoisomers, we must subtract any meso compounds from the total calculated.
Therefore, for 2,3-dibromobutane, we calculate 4 possible stereoisomers (22) and then subtract the 1 meso compound, resulting in 3 unique stereoisomers. Understanding meso compounds helps clarify why not all theoretically possible stereoisomers are observed in practice.