Meso Compounds with an odd number of chiral centers

In summary, during an organic chemistry class, the professor explained that a compound needs two or more chiral centers to be considered meso. The student was able to come up with structures for meso compounds with an even number of chiral centers, but struggled with finding one that had an odd number. The possibility of a compound with an odd number of chiral centers being meso was discussed and an example was given. It was also noted that the terms "stereocenter" and "chiral center" have different meanings and should be used carefully.
  • #1
thefan
2
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I was learning about chirality in my organic chemistry class when we were talking about meso compounds. The professor stated that for a compound to be meso, you needed there to be two or more chiral centers. After thinking about it for a while, I can come up with abstract structures for meso compounds with 2, 4, ..., 2n chiral centers, but can't come up with one that has 2n+1 chiral centers. Is it possible to have a compound with an odd number of chiral centers that is meso?
 
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  • #2
thefan said:
I was learning about chirality in my organic chemistry class when we were talking about meso compounds. The professor stated that for a compound to be meso, you needed there to be two or more chiral centers. After thinking about it for a while, I can come up with abstract structures for meso compounds with 2, 4, ..., 2n chiral centers, but can't come up with one that has 2n+1 chiral centers. Is it possible to have a compound with an odd number of chiral centers that is meso?

Sure, try (1R, 2S,4r)-1,2,4-cyclopentanetriol or similar.
 
  • #4
you have to be careful with how you through around the terms "stereocenter" and "chiral center." If your instructor said "A meso compound cannot have 2n+1 number of CHIRAL centers," then they are correct. It would be incorrect to say "a meso compound that contains STEREOcenters must have 2n stereocenters." In other words, these terms do not have the same meaning. All chiral centers are stereocenters, and not all stereocenters are chiral centers. the term "stereocenter" or "stereogenic center" means that swapping two groups on that center would give a different stereoisomer, whereas "chiral center" means that the atom doesn't occupy a molecular plane of symmetry (4 different substituents bonded to the atom).
 
  • #5


Yes, it is possible to have a meso compound with an odd number of chiral centers. A meso compound is defined as having internal planes of symmetry, which means that the molecule can be divided into two equal halves that are mirror images of each other. This symmetry can occur even with an odd number of chiral centers.

One example of a meso compound with an odd number of chiral centers is tartaric acid (C4H6O6). It has three chiral centers, but due to its internal symmetry, it is considered a meso compound. Another example is meso-2,3-butanediol (C4H10O2), which has two chiral centers but is also meso due to its internal symmetry.

In general, the presence of an odd number of chiral centers does not necessarily mean that the compound cannot be meso. It is the internal symmetry of the molecule that determines whether it is meso or not.
 

1. What are meso compounds with an odd number of chiral centers?

Meso compounds are molecules that contain multiple chiral centers but possess an internal plane of symmetry, making them optically inactive. In the case of compounds with an odd number of chiral centers, the internal plane of symmetry can only exist if there is an odd number of chiral centers in the molecule.

2. How are meso compounds with an odd number of chiral centers different from other meso compounds?

Meso compounds with an odd number of chiral centers are different from other meso compounds because they cannot have a mirror image that is identical to the original compound. This is because the internal plane of symmetry in these compounds can only exist if there is an odd number of chiral centers, making them asymmetric in nature.

3. What are some examples of meso compounds with an odd number of chiral centers?

Examples of meso compounds with an odd number of chiral centers include tartaric acid, which has three chiral centers and an internal plane of symmetry, and 2,3-pentanediol, which has two chiral centers and an internal plane of symmetry. Both of these compounds are optically inactive due to the presence of the internal plane of symmetry.

4. How do meso compounds with an odd number of chiral centers affect polarimetry readings?

Meso compounds with an odd number of chiral centers will not affect polarimetry readings because they are optically inactive. This means that they do not rotate plane-polarized light, unlike other chiral compounds that have an optical activity and will rotate plane-polarized light in either a clockwise or counterclockwise direction.

5. What is the significance of meso compounds with an odd number of chiral centers in organic chemistry?

Meso compounds with an odd number of chiral centers have a significant role in organic chemistry as they demonstrate the concept of internal plane of symmetry and its effect on optical activity. They also have important applications in the synthesis of other chiral compounds, as they can serve as starting materials for creating compounds with a desired stereochemistry.

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