C$.$ Two chiral centers

Many naturally occurring substances, such as carbohydrates and proteins, have many chiral centers. Where these centers are all unique, there should be $2$n isomers, where n $=$ number of chiral centers.

$1.$ Two unique chiral centers

Construct ethane. Then, referring to the picture in the lab manual, make a $2$ chiral center molecule by remove four hydrogen atoms from the model and add two black $($B$),$ a red atom $($R$),$ and a green atom $($G$).$ This model has two unique chiral centers.

You should be able to make three more optical isomers. Draw them and upload them here?

$2.$ Two of the same chiral centers

On each of the four models that you made, remove the red atom $($R$)$ and the green atom $($G$),$ leaving behind the small black atom $($B$)$ and adding two of the large green atoms. You now have models with the same "substituents" on every carbon.

b$.$ Are the remaining two models mirror images?

c$.$ Are they superimposable?

d$.$ Would either be optically active?

$3.$ Meso form

Find the conformations of the meso form, which have a plane of symmetry.

There is only one meso compound. It is optically inactive and is diastereomeric to the optically active isomers in part C$2.$ An example of a molecule with two identical chiral centers is tartaric acid, which is the principal acid in grapes and is a component that promotes a crisp flavor and graceful aging in wine.

Draw the molecule in this conformation and mark the plane of symmetry with a dashed line. Upload your drawing here.