Draw a diastereomer for each of the following.

Name: Problem 47, Chapter 4: Organic Chemistry
Uploaded: 2020-08-01T20:18:18-08:00
Duration: 6 min 27 s
Channel: Freddie Montague
Description: Draw a diastereomer for each of the following.

Key Concepts

Stereoisomerism

Stereoisomerism refers to the spatial arrangement of atoms in molecules that have the same molecular formula and connectivity but differ in the three-dimensional orientations of their atoms. This concept underpins the differences between various types of isomers, including enantiomers and diastereomers.

Chirality

Chirality is a property of a molecule that makes it non-superimposable on its mirror image, often due to the presence of one or more chiral centers. This unique three-dimensional structure is fundamental to understanding stereochemistry and the behavior of molecules in different environments.

Wedge-and-Dash Notation

Wedge-and-dash notation is a graphical method used to depict the three-dimensional arrangement of atoms in a molecule on a two-dimensional surface. Solid wedges represent bonds coming out of the plane towards the observer, while dashed lines represent bonds oriented away from the observer, providing clarity in stereochemical representations.

Diastereomers

Diastereomers are stereoisomers that are not mirror images of each other. They arise in molecules with multiple chiral centers when the configuration is different at one or more (but not all) of these centers. Because they are not exact mirror images, diastereomers typically exhibit different physical and chemical properties.

Transcript

00:01 Question we have to draw diastariumers for the following compounds.

00:04 To do this, we will keep the configuration at one asymmetric center the same, and then at the other asymmetric center, we will change it to be the opposite configuration.

00:13 So starting with part a, we have this molecule here, and first we are going to determine the configurations at the two asymmetric centers that are here and here.

00:21 So this first carbon, you will determine the asymmetric center by ranking the priorities of the groups.

00:27 So the oh has a highest priority since oxygen has the highest atomic number, followed by this two carbon chain, and then the methyl group, and then last the hydrogen.

00:38 So if we draw arrows from 1 to 2, 2 to 3, they go in a clockwise direction, so we would expect this to have our configuration.

00:46 However, the hydrogen is on a horizontal and not a vertical, so the configuration is actually s configuration.

00:53 So we can draw an arrow and show that this asymmetric center has an s configuration.

00:57 We'll do the same thing for this asymmetric center here.

01:00 The oh has the highest priority, followed by the two carbon chain, then the methyl group, and then last the hydrogen, draw arrows from one to two, two to three.

01:10 They go in a counterclockwise direction, but again, the hydrogen, which is the lowest priority group, is not on a horizontal, so the configuration of this asymmetric center is actually r.

01:21 So now if we redraw this compound, we will keep one configuration of an asymmetric center the same, so let's just keep the top on the same.

01:31 Then the second asymmetric center, we will change the configuration to the opposite, so we can do this by alternating the position of the h and the oh.

01:40 So this top is the same.

01:42 We don't have to find that again, but the configuration around this asymmetric center, the oh has the highest priority, followed by this group, and this group arrows from 1 to 2 and 2 to 3 are clockwise, but we would expect our configuration, but the hydrogen is not on a vertical, it's on a horizontal.

02:03 So now we know that configuration is actually s.

02:06 So this has s configuration, and this carbon still has s configuration.

02:11 So this is the diastarium or first compound.

02:15 Moving on to b, we have our two asymmetric centers here and here.

02:21 This first one, if you look at the priorities of the groups, chlorine has the highest priority, since it has the highest atomic number.

02:29 Followed by this two carbon chain that has a chlorine involved, followed by this two carbon chain without chlorine, and then hydrogen last.

02:38 Since the hydrogen is on a hatched wedge, we don't have to interchange any groups.

02:42 So when we draw arrows from 1 to 2 and 2 to 3, they go in a clockwise direction, which is our configuration.

02:49 We don't have to switch anything.

02:55 So this has our configuration.

02:58 This carbon here, chlorine has the highest priority, followed by this group, and then the main.

03:03 Methyl and then the hydrogen last.

03:06 There goes from 1 to 2 and 2 to 3 go in a counterclockwise direction...

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