1. Free Radical Reactions

2. Radical Reactions Chapter 10
Description
Causes of Free Radical Formation
Importance in Biology, Medicine & Industry
Mechanism
Selectivity of Halogens
Anti-Markovnikov Reaction
Ozone Depletion & CFC’s

3. Description
Molecules or Atoms that contain an unpaired electron. .
CH3

4. Description
Heterolysis or Heterolytic
Leads to Ion formation

5. Description Homolysis or Homolytic Cleavage
Leads to Free Radical formation

6. Description
Stabilization- The greater the ability to spread out the burden of the free radical the more stable the compound.

7. Causes of Free Radical Formation
Metabolism
Immune Response
Combustion
Radiation
UV (Sunlight)
Environmental Pollutants

8. Importance in Biology & Medicine
Aging (Link 2)
Cancer
Emphysema
Nitric Oxide
Blood Pressure Regulation
Blood Clotting
Neurotransmission
Immune Response
Metabolism
Wrinkles
Etc.

9. Importance in Biology & Medicine
Antioxidants - absorb free radicals
Vitamin E
Vitamin C
Beta-carotene
Selenium
Lycopene
Melatonin (Link 2)
Source:

10. Importance in Biology & Medicine
Source:

11. Importance in Industry
Polymers (Plastics)
Polyethylene
Telfon
Polystyrene
Combustion
Cracking

12. Mechanism Three major Steps Chain Initiation Step (Initiation)
Chain Propagation Steps (Propagation)
Chain Termination Steps (Termination)

13. Mechanism

14. Mechanism
Chain Termination

15. Selectivity of Halogens

16. Selectivity of Halogens
Reaction Name
First Chain Propagation
Reaction
Enthalpy
Overall Enthalpy
Fluorination
F. + CH4
-130
-432
Chlorination
Cl. + CH4 +8
-101
Bromination
Br. + CH4
+74
-26
Iodination
I. + CH4
+142
+53

17. Selectivity of Halogens
Source:

18. Selectivity of Halogens
Reactivity
Fluorination > Chlorination > Bromination > Iodination
Higher the reactivity the lower the selectivity.
The decrease in electronegativity explains the decrease in reactivity and thus increase in selectivity.

19. Selectivity of Halogens

20. Selectivity of HalogensEa
Collision < 10% > 90%

21. Selectivity of HalogensEa
Collision < 10% > 90%

22. Anti-Markovnikov Reaction
Free Radical Reaction
Ea Driven Reaction

23. Anti-Markovnikov Reaction

24. Anti-Markovnikov Reaction

25. Markovnikov vs. Anti-Markovnikov
Both reactions are Ea driven
In Markovnikov addition the hydrogen adds first
leading to the most stable carbocation.
In anti-Markovnikov addition the Bromine adds first
leading to the most stable free radical.

26. Natural Ozone Reactions
Source:

27. Natural Ozone Reactions
Source:

28. Natural Ozone Reactions
Natural stratospheric ozone equilibrium.
Step 1: O2 +UV( nm) ==> O + O Step 2: O + O2 + M ==> O3 + M* (Produces ozone from oxygen)
Step 3:
A) O3 + UV( nm) ==> O +O2 B) O +O3 ==> 2 O2 (Produces oxygen from ozone)
An equilibrium concentration of ozone occurs

29. Ozone Depletion & CFC’s
CF2Cl2 + hv CF2Cl. + Cl.
Cl. + O ClO. + O2
ClO. + O O2 + Cl.

30. Problems (p.459, 460, 461)
10.2
10.4
10.6
10.8