destroyer orgo 186

[hoyas19]

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i feel like this should be the easiest question ever but i'm totally not getting it. i got the first R but then i'm getting RRR instead of RSS. It says COOH is the highest priority so how can C-3 be S??

 

[ldm0208]

It says COOH is the highest priority so how can C-3 be S??

It says COOH is the highest priority to give you a nice hint about numbering the carbons in the whole structure, not to confuse you with doing R,S configurations on each carbons.

 

[hoyas19]

yeah i figured out numbering but for some reason i just don't understand how they came up with their answer. if COOH is a high priority, then for C-3 shouldn't Cl be#1, the carbon above be #2, and the carbon below be #3 making it S and then you have to switch it to R because of the hydrogen? I don't get why the C-4 would be higher priority than C-2...

 

[ldm0208]

yeah i figured out numbering but for some reason i just don't understand how they came up with their answer. if COOH is a high priority, then for C-3 shouldn't Cl be#1, the carbon above be #2, and the carbon below be #3 making it S and then you have to switch it to R because of the hydrogen? I don't get why the C-4 would be higher priority than C-2...

hoyas, yes Cl be #1. Now when you compare C2 with C3, see the element weight of Br and Cl, which one is heavier? This is why..hope you get it now 🙂

 

[hoyas19]

thanks i get it now =) can you explain 172 then? i understand carbon 3 but but for C-2, is C-Cl or C-OOH a higher priority? I would have thought it was COOH but the answer key says something different..

 

[ldm0208]

but for C-2, is C-Cl or C-OOH a higher priority? I would have thought it was COOH but the answer key says something different..

okay hoyas, to do this R,S config fast and accurate, you first need to know how to do it very clear and then you can jump on the questions espeacially destroyer's qestions.

For 172 carbon #2, let's to it together.
(1)C,(2)Cl vs (1)C,(2)O,(3)O,(4)H
you first compare 1 vs 1, which is C vs C, they are same, so now you compare 2 vs 2, which is Cl vs O. Again here which one is heavier? Cl
It should give you 2R config. But bear in mind the question is asking the enantiomer. So, you just change the R to S and vice versa.