Chapter 5: 5.2 Chirality and Chiral Molecules

There are other kinds of stereoisomers, what is the other type of stereoisomer besides cis/trans?

Charality

What is chirality?

When a molecule and its mirror image are different (like left and right hands). This usually happens when a carbon is attached to four different groups.

What is the chiral center

1. It is part of chirality

2. A carbon atom attached to four different groups in a tetrahedral arrangement

3. There are two ways to spatially arrange the groups on a chiral center.

   1. Ex: Figure 5.3 There are two ways to arrange four different groups around a tetrahedral carbon atom

      1. Consider the structure of sec-butyl alcohol, it has a chiral center which can be arranged in three-dimensional space two different ways

      2. These two drawings represent stereoisomers ( compounds that differe only in the spatial arrangement of their atoms

      3. No matter how muc you mentally flip and rotate the first drawing, you will not be able to get each of the four groups to match up with the four groups on the second drawing- in other words, they are nonsuperimposable

      4. However, the two stereoisomers can mirror each other and that is known as superimposing

Examples of chiral centers

What are the rules of when it is not a chiral center?

1. If going clockwise and counterclockwise around the ring lease you down different environments (like one direction hits a double bond first), then those two paths count as different groups so it is a chiral center

BUT

2. If clockwise and counterclockwise are exactly the same path (they encounter the same atoms in the same order), then the. carbon does NOT have 4 different groups and WILL NOT be a chiral center

3. Ex: it is not a chiral center

DRAW ALL OF THESE

What is the difference between chiral and achiral

1. Chiral

   1. Lacks reflection symmetry

   2. So it does not have a plane of symmetry

2. Achiral

   1. One half of the molecule is the exact mirror image of the other

   2. has a plane of symmetry

For each of the following objects determine whether ot not it possesses a plane of symmetry

yes, it possesses a plane of symmetry

For each of the following objects determine whether ot not it possesses a plane of symmetry

No, no plane of symmetry

For each of the following objects determine whether ot not it possesses a plane of symmetry

No, there is no plane of symmetry

For each of the following objects determine whether ot not it possesses a plane of symmetry

Yes, there is a plane of symmetry

For each of the following objects determine whether ot not it possesses a plane of symmetry

Yes

For each of the following objects determine whether ot not it possesses a plane of symmetry

No

For each of the following objects determine whether ot not it possesses a plane of symmetry

No

For each of the following objects determine whether ot not it possesses a plane of symmetry

Yes

What is an enantiomers?

1. are pairs of molecules that are mirror images of each other but cannot be superimposed, just like your left and right hands

What does it mean for something to be superimposable?

1. If things are mirrored exactly as they are

What does it means when it is non superimposable?

It means that things can mirror, but it won’t be the same

When a compound is chiral, will it have a nonsuperimposable mirror image or a superimposable image?

1. When the compound is chiral, it will have a nonsuperimposable mirror image, called its enantiomer