enantiomers and diasteriomers

1. Stereochemistry of
organic compounds
Optical isomerism: enantiomers and diasteriomers

2. Number of optically active
isomers in a compound
maximum number of optical isomers = 2n
n-number of chiral centres

3. n= 1
maximum number of optical isomers = 2n = 2
n= 2
maximum number of optical isomers = 2n = 4

4. Enantiomers
• Optical isomers whose molecular structures are non-superimposable
mirror images of each other and which rotate the plane of polarized
light equally but in opposite direction
• The phenomenon is enantiomerism
• Isomers that rotate plane polarized light to
• right: dextro rotatory (+) or (d)
• left: laevo rotatory (-) or (l)

5. Properties of enantiomers
• enantiomers have identical physical and chemical
properties
• Enantiomers differ in their rate of reaction towards
optically active compounds and enzymes
• They have different biological activity

6. Chirality in Real life

7. d and l lactic acid

8. d and l asparatine
• (-)asparatine tastes sweet but the (+)asparatine is
bitter

9. amino acids
• Only L-amino acids are manufactured in cells and
incorporated into proteins
• Some D-amino acids are found in the cell walls of
bacteria, but not in bacterial proteins
• Glycine, the simplest amino acid, is not optically
active

10. d and l limonine
smell of orangessmell of lemons

11. d and l thalidomide
The (+) enantiomer has sedative effects whereas the (-) isomer is
teratogenic.

12. d and l glucose
• (+)glucose is an important nutrient while (-)glucose
is of no use in the human body

13. Tartaric acid
optically active
enantiomers
optically inactive
enantiomers

14. Diasteriomers
• Diastereomers are stereoisomers that are not
mirror images of one another and are non-
superimposable on one another.
• May or may not be optically active
• Different physical and chemical properties
1, 2 and 3, 4 – enantiomers
1,3; 1,4; 2,3; 2,4 - diastereomers