Exploring Chiral Molecules: Hands-On Learning with Fischer Projections

1. Chapter 14 Aldehydes, Ketones, and Chiral Molecules 14.5Chiral Molecules

2. Chiral Compounds Chiral compounds • have the same atoms or groups arranged differently in space • have one or more chiral carbon atoms bonded to four different groups • are mirror images like your hands. Try to superimpose your thumbs, palms, back of hands, and little fingers

3. Hands Are Like Chiral Objects

4. Mirror Images The mirror images of • bromochloroiodomethane can align the H and I atoms, which places the Cl and Br atoms on opposite sides • chiral compounds cannot be superimposed

5. Achiral Structures Are Superimposable When the mirror image of an achiral structure is rotated, • the structure is aligned with its initial structure • its mirror image is superimposable

6. Some Everyday Chiral and Achiral Objects

7. Learning Check Identify each as a chiral or achiral compound. A. B. C.

8. Solution Identify each as a chiral or achiral compound. A. B. C. Chiral Chiral Achiral

9. Fischer Projections A Fischer projection • is a 2-dimensional representation of a molecule • places the most oxidized group at the top • uses vertical lines for bonds that go back • uses horizontal lines for bonds that go forward • assigns the letter L to the structure with the —OH on the left • assigns the letter D to the structure with the —OH on the right

10. Drawing Fischer Projections

11. Examples of Chiral Molecules

12. Learning Check Indicate whether each of the following pairs of Fischer projections can or cannot be superimposed.

13. Solution Indicate whether each of the following pairs of Fischer projections can or cannot be superimposed: Cannot be superimposed Can be superimposed