1. Isomerism ,Stereoisomerism &Chirality
LECTURE ONE
Isomerism ,Stereoisomerism &Chirality

2. Isomerism

3. Isomerism ,Stereoisomerism &Chirality.
LECTURE ONE: عضوبة
Isomerism ,Stereoisomerism &Chirality.
The branch of chemistry that deals with the special arrangement of atoms in molecules and the effects of such arrangements on the chemical and physical properties of the molecules, especially where asymmetric centers of substitution lead to optical rotation.
Stereoisomers: isomers that have the same formula and connectivity but differ in their position in space. They posses one or more stereocenters.
Chiral: any molecule that is nonsuperposable with its mirror image. Chiral from Greek word cheir meaning hand.

5. Isomerism ,Stereoisomerism &Chirality

6. Isomerism ,Stereoisomerism &Chirality
Optically Active: The ability of some substance to rotate plane polarized light, {rotates plane-polarized light to the right is called dextrorotatory (+), while to lift is called levorotatory (-)}.
Enantiomers: stereoisomers that are nonsuperposal mirror images.
Racemic mixture: its 1:1 (equimolar) mixture of two enantiomers.

7. Every object has a mirror image. Many objects are achiral
Every object has a mirror image. Many objects are achiral. By this we mean that the object and its mirror image are identical, that is, the object and its mirror image are superposable. While chiral object is one that cannot be superposed on its mirror image.
The Biochemical Importance of CHIRALITY:
The human body is structurally chiral, with the heart lying to the left of center and the liver to the right.
The Biochemical significance of Chirality:
The origin of biochemical properties relating to chirality is often likened to the specificity of a chiral.

8. fig.(2): Enantiomers of Epinephrine to bind specific Enzyme .

9. The enzyme Epinephrine has three binding sites, one specific for A, another for B, and a third for Z . To form an E-S complex, * Only the D-enantiomer can bind to the surface with all three groups attached to the correct binding sites. The L-enantiomer can bind to a maximum of two sites. In this way the enzyme can distinguish between the two enantiomers .
fig.(3): Enantiomers of Epinephrine to bind specific Enzyme .

11. Thalidomide is a racemic mixture
Thalidomide is a racemic mixture. One enantiomer has the intended effect of curing morning sickness & the other enantiomer, may be the cause of the birth defects. Now Thalidomide strict regulations for treatment of some forms of cancer and a serious complication associated with leprosy. Its potential for use against other conditions including AIDS and rheumatoid arthritis.