Resolution of racemic mixture

its my first slide

1. RESOLUTION OF RACEMIC MIXTURE BY IQRAR AHMAD ABRAR AHMAD Department Of Pharmaceutical Chemistry M.Pharm First Year( S em 1) RCPIPER,shirpur 1

2. ENANTIOMERS: Isomers which are nonsuperimposable mirror images of each other are called enantiomers . These are distinguished by 1)+/- 2)D/L (l/-)- enantiomer (anticlockwise rotation) (dl/±)- racemate (no overall effect) (d/+)- enantiomer (clockwise rotation) 2

3. RACEMIC MIXTURE: A equimolar (50/50) mixture of the two enantiomers is called a racemic mixture or a racemate . Enantiomers have identical chemical and physical properties, except:Their effect on plane polarised light. RESOLUTION: the process of seperation of pure enantiomer from their racemic modification is called resolution. 3

4. NEED FOR RESOLUTION OF RACEMIC MIXTURE: CETRIZINE   levocetirizine has been found to be less sedating than cetirizine 4

5. Levodopa levodopa (L-dopa) is used in treatment of Parkinson’s disease, its D-form causes serious side effects,such as granulocytopenia 5

6. 6

7. 1.MECHANICAL SEPARATION OR SPONTANEOUS RESOLUTION: This invoved mechanical separation of the crystal of one enantiomers from the other in racemic mixture based on difference in their shapes Crystal of the two forms have different shapes separated by magnifying lens and forceps This method first used by pasteur for he resolutiuon of sodium ammonium tartarate which crystallise out in the form of racemic mixture below 27 degree This methods is time consuming and every compound can not be crystallized at room temperature 7

8. 2.PREFERENTIAL CRYSTALIZATION BY INOCULATION: This method involve seeding of a saturated solution of the racemic mixture with a pure crystal of one the two enantiomers . The soluition now become suppersaturated with respect to the added enantiomers It begins to crystallise out Eg . Harda obtained free from amino acid by adding corresponding d/ l isomers of amino acid 8

9. 3.BIOCHEMICAL SEPARATION: It was introduced by PASTEUR in 1858. This method is based on fact that when certain micro organisms like bacteria,fungi,yeast,moulds,etc are grown in dilute solution of racemic mixture,they eat up one enantiomer rapidly than other. Example: the mould penicillium glaucum preferentially destroys the (+) isomer of racemic ammonium tartarate leaving (-) ammonium tartarate in solution . 9

10. 4.CHROMATOGRAPHIC SEPERATION: The racemic mixture can be separated by chromatography on an optically active support. The diastereomeric adsorbates which are formed have different stabilities. Thus one enantiomer will be held more tightly than the other and would be eluted first. 10

11. 5.KINETIC METHOD : This method is based on the fact that one of the enantiomer of racemic mixture reacts faster than other with optically active compound. menthol reacts faster with (+) mandelic acid than with (-) mandelic acid. Thus with difference in kinetics of reaction,racemic mixture can be seperated . 11

12. 6.PRECIPITATION: This method is based on formation of precipitate by reaction between any reagent and racemic mixture. Example: (+) & (-) narcotine when dissolved in HCL ,precipitates (+) narcotine . 12

13. 7.BY DIASTEREOMERS: When racemic mixture is allowed to interact with optically active material, it give a diastereomeric derivatives. Diastereomer have different physical properties and hence can easily separated into two component by fractional crystallisation 13

14. REFRENCES: 1. O.P Agrawal , “Organic Chemistry Reaction And Reagent” Goel Publication Fourty Eight Edition 2012 Page No.137-143 2.Ernest L Eliel , “Stereochemistry Of Carbon Compound” Tata Mc Graw -hill Page No.47-75 3.Jerry March, “Advance Organic Chemistry” Fourth Edition Page No.120-124 4 Morrison Boyd, “Organic chemistry”, edition-6,page-133 14

15. “ THANK YOU” 15