The compound below has one stereocenter. Find it, and determine whether it is R or S : IMAGE IS

step 1 So this question is asking us to determine the chiral center. That's the first part of the molec

The compound below has one stereocenter. Find it, and...

Key Concepts

Stereocenter

A stereocenter, sometimes called a chiral center, is an atom in a molecule that is attached to four different substituents, leading to non-superimposable mirror images. This results in molecular chirality, meaning the compound can exist in two enantiomeric forms that are mirror images of each other.

Chirality

Chirality refers to a property of a molecule where it cannot be superimposed on its mirror image. This is an important concept in stereochemistry, as the differences in the spatial arrangement of atoms in chiral molecules can result in drastically different chemical and biological behaviors.

Cahn-Ingold-Prelog (CIP) Priority Rules

The CIP priority rules are a systematic set of guidelines used to assign priorities to the substituents attached to a stereocenter. By ranking the groups based on atomic number and connectivity, these rules provide a standardized method to determine the spatial configuration around the chiral center.

R/S Configuration

The R and S nomenclature is used to describe the absolute configuration of a stereocenter. After assigning priorities using the CIP rules, the molecule is oriented so that the lowest priority group is directed away. The remaining groups are then traced in order of descending priority; a clockwise path indicates an R (rectus) configuration, while a counterclockwise path indicates an S (sinister) configuration.

Transcript

00:02 So this question is asking us to determine the chiral center.

00:06 That's the first part of the molecule.

00:08 And the reason why we need to determine the chiral center is because we need to know what the chiral centers is determined if the molecule is of r or s configuration.

00:17 So the way we're going to figure out the chiral centers, we're going to evaluate the carbons to see which one is surrounded by four different molecules because the chiral center is a carbon that is surrounded by four different molecules.

00:28 So we know that this or this cannot be the chiro center because this is a terminal carbon, so it has to be surrounded by three hydrogens.

00:38 And then this carbon also has to be surrounded by two hydrogens.

00:41 And it's surrounded by two of the same molecules at least, right? so it cannot be the chiro center.

00:47 And for that same reason, this carbon cannot be the chiro center either because it's surrounded by two chlorines.

00:52 And so since it's surrounded by two of the same molecules, it cannot be a chiro center.

00:55 And then none of the carbons in the in the benzene ring over here can be chirocentres either because they're all in double bonds.

01:05 And we know that a chiro center can never be a molecule that is in a double bond.

01:09 So the only carbon that's left is this carbon right over here.

01:12 And we can see that it is the chiro center because it's surrounded by an alcohol on one side.

01:18 And then the other carbon has two chlorines attached, which is very different from the cyclohexane that is on this side.

01:25 And then we that a molecule has to be a carbon has to be surrounded by four different types of molecules so we know that there has to be a hydrogen over here as well so now that we've determined what the chiral center is which i'll label here in purple then the next thing we have to do is we have to determine priority so that we can determine the configuration so what we need to do is we need to determine what has um um greater priority.

01:57 So we can see, so i'm going to label this as a and then this is b and this is c.

02:05 So obviously we know that hydrogen is going to be a least priority because the thing that sets every molecule apart from hydrogen is that this a is surrounded by an ox is next to, this carbon is next to, i'm sorry, my screen keeps minimizing, but we know that in a, the carbon is right next to an oxygen, and an oxygen has greater priority than a hydrogen.

02:28 And c, it's right next to a carbon over here, which has greater priority than a hydrogen.

02:33 And then b, it's next to a carbon, which has greater priority than a hydrogen.

02:37 So hydrogen is, of course, going to be a fourth priority.

02:40 So we can label number four for hydrogen right off the bat...

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