Steriochemistry of organic compounds optical activity : enantiomers and diasteriomers

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 =  2 n n -number of chiral centres

3. n= 1 maximum number of optical isomers =  2 n = 2 n= 2 maximum number of optical isomers =  2 n = 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 oranges smell 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