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.

Question

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.

rushwr · Answer

I'm sorry but can u make the question a little bit more clearer?

photon336 · Answer

Oh, wrote that wrong sorry it was supposed to be: which of the following compounds has an S stereocenter?

Not stereoisomer.

rushwr · Answer

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!

photon336 · Answer

Yeah, so I had to find the chiral carbons in each and then assign either r or s configuration.

rushwr · Answer

yeah ! @Photon336

aaronq · Answer

what's the molecule ?

ciarán95 · Answer

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:
-Bromine
-Hydrogen
-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:
|dw:1437134950790:dw|

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:
|dw:1437135620041:dw| 

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! :)