Thursday, June 16, 2011

IB Chemistry, Stereoisomerism, Optical isomerism, Enantiomers in Organic Chemistry

Stereoisomers, Enantiomers, Optical Isomers and Polarimeter
Stereoisomerism are isomers with same Molecular Formula + Structural Formula but different in spatial arrangement ( different 3 Dimensional shapes )

2 types of stereoisomers  for ORGANIC compounds
  • geometrical
  • optical 

Optical Isomers (ORGANIC)
  • Chiral or Asymmetrical Carbon 
  • 4 different gps attached to carbon central
  • Non superimposable
  • Mirror image ( right, left handed )
  • Enantiomers
  • Identical chemical/physical properties 
  • 2 enantiomers rotate plane of polarised light to diff directions
Optical isomers (Thalidomide) tragedy due to Mirror Image
Thalidomide drug exist as optical isomers, 
  • Enantiomers (R) and (S)
  • (R) effective against  insomnia and morning sickness
  • (S) teratogenic, birth and limb defect






In nature, our body synthesises enzyme which have active site for only one enantiomer
  • Drug company, synthesise racemic mix (R)/(S) which is cheaper.
  • (R) is effective but (S) has side effect.
  • Enzyme recognises only one enantiomer due to active site


Mirror image of thalidomide caused limb deformation
  • (S) enantiomer causes limb defects and severe shortening of the arms /legs.
  • (R) enantiomer is effective drug
  • Body will convert (R) to (S) by racemisation process, producing a racemic mixture (R)/(S)
source:http://chemwiki.ucdavis.edu/index.php?title=Special:Userlogin&returntomypage=y


Mirror Image of Ibuprofen (pain killer drug) has no side effect
  • (S) enantiomer, effective in reducing fever and pain relief
  • (R) enantiomer has no side effect
  • Most drugs in racemic mix equal (R) and (S)
  • Cheaper to synthesise racemic mix
  • Single enantiomer (Expensive) but appears to be more effective than racemic mix
  • Clinical trial essential to ensure no harmful side effect
  • Most racemic drugs (R)/(S) have little side effect
  • Thalidomide (R)/(S) was disaster!!!!!!




    sourcehttp://www.chemconnections.org/organic/chem226/Labs/opt-rotation/ibupro-resolution-09.html
    ....................................................................................................................................................
    IB Keywords
    • Enantiomers - pair of non superimposable isomer, (mirror image), (diff 3D shapes)
    • Isomers - compounds with same MF + SF but diff spatial arrangement
    • Racemic - equal (50/50)% mixture of both enantiomers (S) and (R) ( optically inactive ), no net rotation of plane-polarized light, rotations cancel out each other, present in equal amounts.
    History of Thalidomide
    1954 -   Thalidomide for  insomnia and morning sickness.
    1961 -   Withdrawn, teratogenicity, birth defects, if drug is taken during pregnancy.


    1990 - FDA approved  for erythema nodosum leprosum,  leprosy (skin disease) 
    1998 -  FDA approved for multiple myeloma, (cancer of plasma cells in the blood) 


    2004 - Lenalidomide derived from Thalido able to strengthen immune cells and effective against blood cancers
    2011 - Thalidomide + Lenalidomide inhibit formation of new blood vessels ( anti-angiogenic) of tumor cells, Tumors unable to grow/spread due to lack of nutrition. Researchers testing thalidomide in trials for  HIV and Crohn’s disease.
    Video Tutorial, Stereoisomerism, Enantiomers, Optical Isomers

    ......................................................................................................................................................
    Video, Thalidomide, Enantiomers/Mirror Image/Chiral Carbon

    Thalidomide making a come back after named as the greatest disaster in medical history



    Click HERE to view video on the Return of Thalidomide/Lenalidomide
    Keynotes from video 
    • Why rejuvenate it despite so deadly to pregnant women?
    • Able to treat Blood and Bone marrow Cancer.
    • Kept away for 20 yrs since disaster, rejuvenated after 30% cancer patient recovered
    • Caution and seek professional medical advice
    • No pregnant women allowed, US approved it
    • Why no new drugs to replace old Thalidomide drug?
    .....................................................................................................................................................
    Scientists discovered How Thalidomide caused Malformed Limbs
    March 2010 - Published in Science by Takumi Ito.
    Click HERE for info/source
    Defect Limbs due to Thalidomide
    • (S) enantiomers binds/inactivates the protein cereblon, which is important in limb formation. Inactivation, leads to a teratogenic effect on LIMB DEFORMITIES

    Published in Science, March 2010
    • Hiroshi Handa /Takumi Ito - Developed tiny beads (200 nm) with Thalidomide attached.
    • Thalidomide beads mix with cells extract
    • Protein Cereblon was bounded on beads
    • Lack of Protein Cereblon during embryo development, causes limb deformities


    ..........................................................................................................................................................
    Polarimeter



    Optical Isomers have
    • Same MF, SF but differ in spatial arrangement.
    • Same physical/chemical properties
    • Differentiated using polarimeter, optically active enantiomers, rotate plane of polarised light in diff direction
    picture from
    http://www.creation-science-prophecy.com/amino/


    ........................................................................................................................................................
    IB Keywords
    • Optically active enantiomers rotate plane of polarised light (clock/anticlockwise)
    • Enantiomers have same physical/chemical properties
    • Enantiomers present in equal amt (racemic mix), one enantiomer will rotate light to one dir, another will rotate to same degree but opposite dir (rotation cancel out each other), OPTICALLY INACTIVE
    • Natural products (body) produce only 1 PURE enantiomer (OPTICALLY ACTIVE)
    • Synthetic products produce 2 enantiomers, (racemic mix), (OPTICALLY INACTIVE)
    Video, Polarimeter in distinguishing optically active enantiomers

    Thanks to all pictures and video contributors for the above post

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    1. Thalidomide is a drug used in the treatment of leprosy. In the late 1950s, thalidomide was prescribed to expectant mothers to treat morning sickness, anxiety, and insomnia. A decade later, the Food and Drug Administration took the drug off the market after more than 10,000 babies exposed to thalidomide in the womb were born with severe adverse thalidomide birth defects including serious malformations and limb deformities.

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