Stereochemistry

Basics of stereochemistry.

1. ORGANIC TRANSFORMATIONS Presented by: Zia Ur Rehman

2. Stereochemistry Chemistry In Three Dimensions

3. ISOMERS Different compounds having same molecular formula but different structures.

4. S tructural Isomers / Constitutional Isomers : Distinguishable by two dimensional structure The sequence in which the atoms are bonded to each other in the molecule. e.g . C 4 H 10 butane

5. Stereoisomers: Distinguishable by three dimensional structure Isomers that differ in the way the atoms are oriented in space, but not in which atoms are bonded to which atoms. e.g . cis -2-butene trans -2-butene

6. Conformational Isomers Stereoisomers which are interconvertible simply by rotation of one part of the molecule with respect to other about a single bond. Eclipsed conformation: C-H bond opposite to each other Staggered conformation: C-H bonds at maximum distance

7. Stereoisomers which are not interconvertible without breaking and making the bonds, and can be isolated Configurational Isomers

8. A chiral object is that which has non superimposable mirror image. Chirality

9. An atom with four different groups attached to it, is called chiral atom and also called chiral center. Chiral Center

10. Any object that has a plane or point of symmetry is achiral (not chiral). An atom with four different groups are not attached to it, is called achiral atom. Achiral

11. Enantiomers are stereoisomers that are non- superimposable on their mirror images. Enantiomers

12. Diastereomers are stereoisomers that are not mirror images of each other – they are stereoisomers that are not enantiomers . Diastereomers

13. The property of enantiomers to rotate the plane polarized light towards left or right. Compounds that rotate plane polarized light to the right (clockwise) are called dextrorotatory, ( d ) or (+). compounds that rotate plane polarized light to the left (counter-clockwise) are called levorotatory ( l ) or (-). Optical Activity

14. Light that has been passed through a nicol prism or other polarizing medium so that all of the vibrations are in the same plane. plane polarized light non-polarized polarized

15. Polarimeter It is used to measure thr optical activity of a compund .

16. Specific Rotation The angle of rotation of plane polarized light by a 1.00 gram per cm -3 sample in a 1 dm tube . [ α ] D (D = sodium lamp, λ = 589 mμ). α [ α ] D = where α = observed rotation l * d l = length (dm) d = concentration (g/cc) (+)- alanine [ α ] D = +8.5 (-)- lactic acid [α ] D = -3.8

17. Drawing Enantiomers Fischer Projection: Newman Projection:

18. R,S-System The atom of higher atomic number has the higher priority. 1 2 3 4 ( S )-2-bromobutane

19. Erythro isomer has two identical substituents on the same side and the threo isomer has them on opposite side. Erythro,Threo -System

20. Syn describes groups on the “same” face while anti describes groups on “opposite” face. Syn,Anti -System

21. If the two groups with the higher priorities are on the same side of the double bond, that is described as the (Z)- isomer. If the two groups with the higher priorities are on opposite sides of the double bond, then this is the (E)- isomer. E,Z-System

22. Contains chiral center but their mirror images are non superimposeable. Meso Compound

23. An equimolar mixture of a pair of enantiomers is called racemate or racemic mixture. It is denoted by symbol ( ). Racemic Mixture

24. A stereoselective reaction can produce multiple stereoisomers theoretically, but more of some produced than others. Stereoselective Reaction Prominent

25. A stereospecific reaction produces different stereoisomer products from different stereoisomer reactants. Stereospecific Reaction

26. Since most of the natural ( biological) environment consists of enantiomeric molecules (amino acids,nucleosides , carbohydrates and phospholipids are chiral molecules), then enantiomers will display different properties. Then, in our body: Biological Significance of Chirality

27. Food Technology D-Amino acid is purposeful in fermented products such as cheeses, yoghurt, wine or viniger . “L” form of glutaminic acid is the carrier of taste such as meat, brothy or umami taste. In plant essential oils In fruit flavor

28. Pharmaceuticals

29. Polymers Chiral stationary phases in high performance liquid chromatography (HPLC ). Asymmetric catalysis applications. Chiral liquid crystals in ferroelectrics and nonlinear optical devices ( cholesteric liquid-crystalline oligomers ). Very soluble, optically active, potentially ion exchangeable, and thermally stable chiral polymers are synthesized (poly(hydra- zide - imide )s containing ethyl L-lysine ester). Pressure-Sensitive Touch Panel Based on Piezoelectric Poly(L-lactic acid) Film.