Which of the following has an S stereoisomer?
Originally thought this was A, b.c the bromine takes highest priority, followed by the two carbons to the left of it and then the one with the double bonds giving 1-2-3 counterclockwise.
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I'm sorry but can u make the question a little bit more clearer?
Oh, wrote that wrong sorry it was supposed to be: which of the following compounds has an S stereocenter?
It's not clear for me again . I think I can't understand sorry about tht. But the easiest way to find a stereocenter is finding the chiral carbon which is attached to 4 different groups or elements!
Looking at the four structures, I actually found two stereocentres with an S-configuration.....
In (A.), as you rightly said, there is a stereocentre at the carbon with the bromine bonded to it. The four different groups bonded to it are:
-Two different parts of the carbon ring structure.
Determining priorities based on molecular weight, we can clearly see that Br will have the highest priority (Number 1) and H the lowest (Number 4). But, what about the other two groups?
Well, both have a carbon bonded to the stereocentre, but if we look at what is bonded to these carbons we can differentiate:
One carbon (left-hand side above) is directly bonded to two hydrogens and a carbon, whilst the other (right-hand side) is bonded to two carbons and a hydrogen. This becomes the first point of difference along their chains, and so the greater weight of the carbon over the hydrogen determines the priority here:
I also thought there was one at the carbon bonded to the flourine in (D.), whilst the rest all seemed to be of R-configuration (clockwise going from 1 -> 2 -> 3 priorities). Were you able to spot this one @Photon336 .... it's a while since I done these so I might have been a bit rusty! :)
@Ciarán95 Thank you so much for the explanation that made sense! I wasn't completely sure, but the whole thing about the C=C bond made sense you treat is as two C-C single bonds.