How many chirality centers are there?

[skyisblue]

How many chirality centers are there in 2,4-dibromo-3-chloropentane?

I say there are three; hence, there are a maximum of 8 possible stereoisomers for this compound.....

However for the answer, there is a pair of enantiomers, which counts for 2 stereoisomers out of the 8 possible AND 2 meso stereoisomers which counts for 4 of the stereoisomers out of the 8 possible....6 of the stereoisomers are now accounted for, but that leaves 2 stereoisomers left.....where are these 2stereoisomers??

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[Streetwolf]

How many chirality centers are there in 2,4-dibromo-3-chloropentane?

I say there are three; hence, there are a maximum of 8 possible stereoisomers for this compound.....

However for the answer, there is a pair of enantiomers, which counts for 2 stereoisomers out of the 8 possible AND 2 meso stereoisomers which counts for 4 of the stereoisomers out of the 8 possible....6 of the stereoisomers are now accounted for, but that leaves 2 stereoisomers left.....where are these 2stereoisomers??

You have a pair of enantiomers and a pair of meso which equals 4 total. I don't know where you're getting 6 from.

There are only 2 chirality centers - C 2 and 4. C3 is not because two of the substituents are identical (hint: not the H and not the Cl).

 

[Lonely Sol]

You have a pair of enantiomers and a pair of meso which equals 4 total. I don't know where you're getting 6 from.

There are only 2 chirality centers - C 2 and 4. C3 is not because two of the substituents are identical (hint: not the H and not the Cl).

Yea, streetwolf is right, the two R chains are identical thereforce C-3 is not a chiral center!

 

[skyisblue]

You have a pair of enantiomers and a pair of meso which equals 4 total. I don't know where you're getting 6 from.

There are only 2 chirality centers - C 2 and 4. C3 is not because two of the substituents are identical (hint: not the H and not the Cl).

They are not identical if carbon 2 and 4 have different configurations. that's how they are meso because there's a plane of symmetry. So there are 3 chirality centers, which would lead to 8 possible stereoisomers. 2 meso compounds does account for 4 stereoisomers when you think about its mirror image as well. But as you know for a meso it's superimposable onto its mirror image so we count its mirror image blindly. So the two meso cpds counts for 4 out of the 8....the pair of enantiomers count for 2 of the 8 possible stereoisomers. we now have 6 and that leads to 2 left unaccounted for.

anyhow, i'm moving on out of stereochemistry.

i doubt the orgo part of the DAT will be this picky...

 

[Streetwolf]

You completely missed what I said. There are only 2 chirality centers, thus only 4 stereoisomers.

C3 is achiral.

 

[Mila]

They are not identical if carbon 2 and 4 have different configurations. that's how they are meso because there's a plane of symmetry. So there are 3 chirality centers, which would lead to 8 possible stereoisomers. 2 meso compounds does account for 4 stereoisomers when you think about its mirror image as well. But as you know for a meso it's superimposable onto its mirror image so we count its mirror image blindly. So the two meso cpds counts for 4 out of the 8....the pair of enantiomers count for 2 of the 8 possible stereoisomers. we now have 6 and that leads to 2 left unaccounted for.

anyhow, i'm moving on out of stereochemistry.

i doubt the orgo part of the DAT will be this picky...

Even if C2 and C4 have different configurations, those two R groups coming off of C3 are still identical. The configurations are irrelevant when trying to figure out group priority.
Thus, as Streetwolf and Lonely Sol mentioned, there are only 2 steriocenters in 2,4-dibromo-3-chloropentane - C2 and C4.
C3 is not chiral because it has two identical substituents (which will be identical whether or not they have different configurations).