Chirality

1
Chapter 15

• Chirality

2
Enantiomers

• Mirror images of molecules are called
  enantiomers. These are non-superimposable.
• An enantiomer contains at least one chiral carbon.

3
Chiral Carbons

• Must have four bonds
• All four legs must be different

4
Stereocenters

• Chiral carbons are stereocenters.
• The number of possible isomers is 2n
• where n is the number of chiral carbons.

5
Polarimeter
0

6
Polarimeter

• Plane-polarized light is passed through the
  sample. (Polarized sunglasses)
• If the solution is not optically active, the
  light remains unchanged.
• If the solution is optically active, the light
  is rotated either to the right or the left.
• Dextrorotatory right
• Levorotatory left

7
Biological Importance

• Chiral molecules react only with specific
  reagents. D-glucose will react with yeast to
  make alcohol, L-glucose will not.
• Enzyme chemistry is very specific with chiral
  molecules.

8
Which Are Chiral?

• 2-chloropentane

9

• 3-chloropentane

10

• 3-chloro-1-butene

11

• 1,2-dichloropropane

12
glucose

• 2,3,4,5,6-pentahydroxyhexanal