Destroyer OC #80 Please Help

[doc1986]

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Can someone explain to me why the solution says there are 3 chiral carbons. I see only 2. The one labeled "1" does not look chiral to me. I was always under the impression that if you go around the ring and there is symmetry than it can't be chiral...So there are not 4 different groups attached to the carbon technically, only 3...right?

 

[fodog]

Yeah--I'm pretty sure there are only 2 chiral carbons in this molecule. I agree with your reasoning

 

[doc1986]

WAIT, I think I might know why it is indeed chiral. Because the ring is an odd number (7)...so going around one way is different than going around the other.

 

[doc1986]

ALSO: Another question I had involves assigning priority (i.e., 1, 2, 3, 4) on the substituents to determine R or S chirality. I am confused in destroyer (mostly fisher projections like #210) questions. In this example, we have a Cl and H as our 1 and 4. The remaining substituents are both attached to a carbon. One carbon is attached to three O's and the other is attached to an H, C and Cl. Three O's have a total higher atomic weight than H, C, and Cl. So since priority is based on atomic number, wouldn't the first group with three O's attached be labled 2 rather than 3? Or does it just depend on which group has the highest? Hope this isn't confusing...

 

[UCB05]

You look for the first difference in connectivity to determine priority. In this case, C-Cl > C-O. You don't add the atomic numbers of all the substituents together. Cl trumps 3 O's