Assign R or S configurations to the chirality centers in the following molecules:

Name: Problem 43, Chapter 5: Organic Chemistry
Uploaded: 2020-06-24T12:41:29-08:00
Duration: 2 min 36 s
Channel: Travis Maslanik
Description: Assign R or S configurations to the chirality centers in the following molecules:

Assign R or S configurations to the chirality centers in the...

Key Concepts

Chirality Centers

A chirality center refers to an atom—most commonly a carbon—that is attached to four different substituents, giving rise to non-superimposable mirror images. These centers are key in determining the stereochemical properties of molecules because the spatial arrangement of their substituents influences the molecule's overall shape and reactivity.

Cahn-Ingold-Prelog Priority Rules

These rules provide a systematic method for ranking the substituents attached to a chiral center based on their atomic numbers and connectivity. This ordered ranking is essential for assigning the absolute configuration of the chiral center by ensuring that the substituents are considered in a standardized way.

R/S Configuration

The R or S designation indicates the absolute configuration at a chiral center. After assigning priorities to substituents following the Cahn-Ingold-Prelog rules and orienting the molecule so that the lowest priority group is directed away from the observer, if the sequence of the three higher-priority groups proceeds in a clockwise direction it is termed R (rectus); if it proceeds counterclockwise, it is termed S (sinister).

Wedge and Dash Notation

This notation is a visual tool used to depict the three-dimensional arrangement of atoms around a chiral center. In molecular drawings, a solid wedge represents a bond coming out of the plane towards the viewer, while a dashed line represents a bond receding into the plane. This convention helps chemists visually analyze and assign R/S configurations by clearly displaying the orientation of the substituents.

Transcript

00:01 So this question asks us to give the configuration for each of the chiral centers and each of the molecules.

00:08 So looking at organic compound a here, we see that the carbon, the screen dot here is going to be the chiral center because it is connected to four different groups.

00:18 We have the hydrogen, the alcohol group, the ethel group, and the methyl group.

00:23 And so we can go ahead and label our designate priorities in order to figure out our configuration.

00:30 So we know that our alcohol group is going to be prior to number one.

00:33 Our ethical group is going to be priority number two.

00:35 Our methyl group is going to be prior to number three.

00:37 And then our hydrogen is going to be prior to number four.

00:40 So it looks like we are going in the clockwise, which we would normally say that's going to be in the r configuration.

00:47 However, we're going to need to invert that because we want the hydrogen to be going away from us, because here we have it going towards us.

00:54 So our absolute configuration here is going to be s.

00:58 For compound b, we know that this particular carbon here is going to be our chiral center because we have four different groups.

01:04 We have our chloral group, our hydrogen group, our phenyl group, and our method group.

01:08 So we can go ahead and assign priorities to figure out our configuration.

01:12 So we know our chloro group is going to be number one...

Please give Ace some feedback