00:01
Okay, let's look at this first molecule that we've got.
00:04
Up to bromine, down to the right iodine.
00:09
Okay, then we've got chlorine here and a wedge to hydrogen.
00:19
All right.
00:21
First things first, we've got to assign priority.
00:23
Iodine has the highest mass.
00:25
That's one, then bromine, then chlorine, then hydrogen.
00:29
Okay, so we'll notice that our highest, lowest priority group is not in.
00:33
In the back.
00:34
So we have a few options.
00:35
We can either rotate it such that it is in the back.
00:38
Or we can just go one, two, three.
00:42
Okay, that's counterclockwise and know that if the lowest priority substituent is not in the back, counterclockwise means r instead of s.
00:52
It would mean s if the lowest priority substitute are in the back, but it's not.
01:00
We know that this is r.
01:02
Okay, next example.
01:09
Equatorial oh h is equatorial oh h and we've got hydrogen here and a hydrogen here okay so basically this is equivalent to the following okay so it is indeed a stereogenic right so what is it let's start here because we've got the lowest priority substituent in the back oxygen is one then the carbon attached to oxygen is two the ch2 is 3 and hydrogen is 4.
01:55
Lowest priority substitute is in the back.
01:57
So counterclockwise does mean s.
02:04
Okay.
02:05
Now, i know for a fact that this is r.
02:11
How do i know that? sorry, i know for a fact that it's s.
02:17
But i know that.
02:18
I know that because miso compounds, meaning if we put a wedge here and a wedge here.
02:27
Such that this had a line of symmetry and was no longer stereogenic.
02:33
It's only possible when we have things like sr or rs, but we can't get meso compounds when we have ss or rr.
02:41
It's impossible.
02:42
They have to have alternate stereochemistry.
02:45
So since this isn't meso, it has to be ss.
02:49
Well, that's a shortcut, but we can still go through the long way.
02:52
Because that probably potentially made no sense.
02:55
So let's, let's actually do it.
03:03
All right.
03:06
So we know there's a hydrogen in front.
03:09
Okay, oxygen is the highest priority.
03:11
This carbon is the second.
03:12
This carbon is the third.
03:14
Hydrogen is the least priority.
03:16
Then we go one, two, three.
03:18
That's clockwise...