Chirality Center Configuration

[skyisblue]

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First off, my camera sucks! I'm in need of a new one.....

I was working on this problem, and I got the answer wrong according to the solution guide.

There are 4 chirality centers for this molecule: one on top next to the carbonyl group, and 3 on the bottom.

The one on the far left is suppose to have an R configuration, but when I've worked out the problem myself I think it has S configuration.

This chirality center is attached to a DASHED OH group, a WEDGED H, and the rest are solid lines. BTW, the Oxygen on top is a carbonyl group.

This is my thinking.....the OH group has priority 1, then the group with the carbonyl group has priority 2, the group with the double bond gets priority 3. The arrow then moves in an R direction, BUT since the H, the fourth priority group is wedged, I conclude that the configuration is S direction.

 

[Lonely Sol]

The thing is, look at the alpha carbon on each side of the chiral center, one on the right is tertiary while the one on the left is secondary, therefore the chain on the right gets the 2nd priority and chain on the left gets the 3rd priority, which gives the chiral center S configuration, then since H is facing outward, it is opposite, therfore it gets and R configuration

 

[Lonely Sol]

double post, sorry

 

[BodybldgDoc]

The thing is, look at the alpha carbon on each side of the chiral center, one on the right is tertiary while the one on the left is secondary, therefore the chain on the right gets the 2nd priority and chain on the left gets the 3rd priority, which gives the chiral center S configuration, then since H is facing outward, it is opposite, therfore it gets and R configuration

I agree.👍

 

[skyisblue]

The thing is, look at the alpha carbon on each side of the chiral center, one on the right is tertiary while the one on the left is secondary, therefore the chain on the right gets the 2nd priority and chain on the left gets the 3rd priority, which gives the chiral center S configuration, then since H is facing outward, it is opposite, therfore it gets and R configuration

I didn't know that that's how one assigns priority to different substitutent groups. How about Cahn-Ingold-Prelog rule? According to these rules, wouldn't the secondary chain get the second priority, because there's a carbon that is bonded to 2 Oxygens in the carbonyl group?

 

[Lonely Sol]

I didn't know that that's how one assigns priority to different substitutent groups. How about Cahn-Ingold-Prelog rule? According to these rules, wouldn't the secondary chain get the second priority, because there's a carbon that is bonded to 2 Oxygens in the carbonyl group?

From what I know, you go carbon by carbon, until a priority can be assigned, in this case you dont have to go as far as C=O group to figure it, since before that there is already one bigger (maybe not the right word to use) than the other.

 

[skyisblue]

From what I know, you go carbon by carbon, until a priority can be assigned, in this case you dont have to go as far as C=O group to figure it, since before that there is already one bigger (maybe not the right word to use) than the other.

I'm going carbon by carbon, but I still find the secondary carbon chain to have greater priority. Where is it "bigger?"