reaction of scavengers it is very useful. it helps to undersrand the reaction.

1. Reaction Intermediate
Free Radical Scavangers

2. Definition
 A free radical is a molecule or molecular
fragment that contains one or more unpaired
electrons in its outermost orbital.
 Free radical is generally represented by
superscript dot.

4. Properties of free radicals
o They are electrically neutral and carries no
charge
o Highly reactive
o Paramagnetic
o Carbon atom in free radical is sp2 hybridized
o They are stabilized by resonance

5. Generation
 Methods of preparation:
1- Photolysis
2-Thermolysis
3- Oxidation reduction reactions

6. 1-Photolysis

7. 2-Thermolysis
 Compounds containing weak bonds often
produce free radicals when subjected to
heat.

8. 3-Redox reactions

9. Mechanism of Free Radicals

11. 1- Addition
Tetrachloroethylene

12. 2- Displacement

13. 3- Rearrangement
3,3 diphenyl butyric acid

14. Free radical scavengers
 free radical scavenger A substance,
also known as antioxidant, that helps
protect cells from the damage caused
by free radicals.
 Free radicals are unstable molecules
that are made during normal cell
metabolism

17. Applications of free radical
scavengers
 Glutathione peroxidase (enzyme)
which reduces H2O2 to H2O.
 Vitamin E (alpha tocopherol) prevent
the peroxidation of membrane
phospholipids and avoid cell membrane
damage through its antioxidant action.
 Vitamin E known as ‘chain breaking
antioxidant’ , It also stimulates the immune
response.

18.  Beta carotene is precursor of vitamin A
and also have antioxidant effects, it also
protect cell membrane lipids from harmful
effects of oxidative degradation.
 Melatonin is a hormone and is scavenger
of free radicals mainly of OH radicals.
 Selenium is a trace element which
enhances the antioxidant activity of
Vitamin E
 Polyphenolic antioxidants (flavanoids)
also possess good antioxidant activity

19.  Vitamin C (ascorbic acid) directly
scavanges O2, H2O2 , OH , it also
contributes toVit E generation.
• Garlic, grape fruit, soya bean, tumeric,
tomato have excellent radical scavenging
activity

20.  Uric acid also plays role in scavenging the
OH radical in body.
 Albumin can scavenge the free radical
forming on its surface.
 Antioxidants are also helpful in
preventing cancer and neutralizes the
substance that damages genetic material.