1. By: Mdm Rohazita Bahari ERT 102 Organic Chemistry 2017 2018
STEREOCHEMISTRY
By: Mdm Rohazita Bahari
ERT 102 Organic Chemistry

2. ISOMERS
Isomers –
Compound with the same molecular formula but different structures
Constitutional Isomer –
differ in the way their atoms are connected.
Stereoisomer(Configurational isomer)-
differ in the way their atom are arranged in space
Devided by 2 types :Cis-trans isomers + isomers that contain asymmetric centers or known as chirality center.

3. ISOMERS

4. CONSTITUTIONAL ISOMERS
Differ in the way their atoms are connected Example:
C2H6O
C4H9Cl

5. CONFIGURATIONAL ISOMER Cis-Trans Isomers
Cis–trans isomers (also called geometric isomers) result from restricted rotation.
Restricted rotation can be caused either by a double bond or by a cyclic structure.
Cis isomer has the substituent on the same side of the double bond
Trans isomer has the substituent on opposite sides of the double bond.

6. Cis-Trans Isomers(Example)
Cis- isomer
Trans- isomer

7. CONFIGURATIONAL ISOMER An Asymmetric Center
Also known as a chirality center.
An atom bonded to four different atoms or groups.

8. Chiral vs achiral CHIRAL ACHIRAL Nonsuperimposable mirror image.
Its mirror image is not the same as itself.
ACHIRAL
Superimposable mirror image.
It looks the same in the mirror

9. Enantiomers
YELLOW
GREEN
BLUE

10. Drawing Enantiomers Perspective formula
Solid lines – bonds in the plane of the paper
Solid wedge- coming out of the paper toward you
Hatched wedge - going back into space behind the paper
The solid wedge and hatched wedge must be adjacent to one another.

11. Drawing Enantiomers Fischer projection
Horizontal line – The bonds project out of the plane toward the viewer
Vertical line- The bonds extend back from the plane away from viewer
The carbon chain usually drawn vertically

12. The higher the atomic no. the higher the priority
Naming Enantiomers
The R,S system of nomenclature
1.Rank the groups (atoms) bonded to the asymmetric center in order to priority
The higher the atomic no. the higher the priority

13. Naming Enantiomers The R,S system of nomenclature
2.Orient the molecules
Lowest priority (4) directed away from you.
3.Draw imaginary arrow from the group of highest priority to the next highest priority
If the arrow point clockwise (R-Configuration)
Counterclockwise
(S-Configuration)

14. Naming from the Perspective Formula
1. Rank the groups bonded to the asymmetric center with the lowest priority group in the back.

15. 2. If the group (or atom) with the lowest priority bonded by a hatched wedge; Clockwise-R;Anticlockwise-S
3. If the group (or atom) with the lowest priority IS NOT bonded by a hatched wedge; then switch two groups so group 4 is bonded by a hatched wedge

16. Configuration from the Fischer Projection
1. Consider the 3-dimensional equivalent to the Fischer Projection.
2. Rank the groups (or atoms) that are bonded to the asymmetric center and then draw an arrow from the highest priority (1) to the next highest priority (2).

17. 3. If the lowest priority is on a vertical bond; clockwise (R-Configuration),Counterclockwise (S-Configuration)
4. If the lowest priority is on a horizontal bond, the configuration is opposite to the direction of the arrow.

18. ISOMERS WITH MORE THAN ONE ASYMMETRIC CENTER
Max no stereoisomer = 2n
n= no. of asymmetric center

19. Diastereoisomers
Stereoisomers (1) and (2) Stereoisomers (3) and (4) Stereoisomers (1) and (3),(1) and (4),(2) and (3), (2) and (4)
ENANTIOMERS
DIASTEREOISOMERS
Diastereoisomers are stereoisomers that are not enantiomers

20. Identification of Asymmetric Carbons
in Cyclic Compounds

21. Meso compounds are achiral molecules with asymmetric centers
Have two or more asymmetric centers and an internal plane of symmetry (-plane)
Meso compounds are achiral molecules with asymmetric centers

22. If a compound with two asymmetric centers has the same
four groups bonded to each of the centers, one of its
stereoisomers will be a meso compound

23. THE END
THANK YOU