This is MSJChem. In this video I'll be looking at optical isomerism. Optical isomerism is shown by compounds that have a chiral or asymmetric carbon within the molecule. A chiral carbon is a carbon atom bonded to four different atoms or groups. Here we have two examples of molecules that have a chiral carbon, which is indicated by the red asterisk.
If we look at the chiral carbon atom in butan-2-ol, we can see that it's bonded to four different atoms or groups. On the right, we have a molecule of lactic acid which also has a chiral carbon atom. And as you can see, it's bonded to four different atoms or groups.
The four groups can be arranged in two three-dimensional configurations, which are mirror images of each other. The two mirror images are non-superimposable. and are known as enantiomers. So here we have the two optical isomers or enantiomers of butan-2-ol. When drawing optical isomers we use the stereochemical formula which shows the spatial arrangement of atoms in a molecule.
The two optical isomers are drawn as mirror images of each other with a mirror in the middle. Here we have the 3D models of the two optical isomers of butan-2-ol. As you can see they are mirror images of each other and non-superimposable. Next we look at the two optical isomers of lactic acid. Just like in the previous example, the two optical isomers are drawn as mirror images of each other using the stereochemical formula.
The two optical isomers are optically active with plane polarized light. This means they rotate the plane of plane polarized light in opposite directions. And we'll look at this in more detail in the next video.