1. Chemistry

2. Properties of alkenes

3. Session objectives Chemical reactions of alkene
Addition of hydrogen, halogen, hydrogen halides
Markownikoff’s rule
Anti-Markownikoff’s rule
Hydroboration-oxidation
Oxymercuration-demercuration
Oxidation of alkene
Ozonolysis
Conjugated dienes

4. The ease of hydrogenation
Addition of Hydrogen
The ease of hydrogenation
Addition takes
predominantly cis manner.

5. Addition of Halogens
Brown
Colourless
Test of unsaturation

6. Mechanism
Step I
Step II
stereospecific reaction

7. Types of reaction Stereospecific reaction Stereoselective reaction
Cis-isomer (major)

8. Addition of hydrogen halides
HI > HBr > HCI > HF

9. Markownikoff’s rule
Polar addition to an unsymmetrical alkene takes place in such a manner that the negative part of the addendum attaches to that carbon atom which is more highly substituted (or contains the least number of H atoms)

10. Markownikoff’s rule

11. Markownikoff’s rule
If HBr is added to a symmetrical alkene, only one product is obtained.
Markownikoff’s addition product depends on the stability of intermediate carbocation.

12. Markownikoff’s rule

13. Markownikoff’s rule
Mechanism

14. Markownikoff’s rule

15. Peroxide effect (Anti Markownikoff’s addition)
Mechanism:

16. Addition of water (Hydration)
Acid catalyzed addition of water

17. Hydroboration–oxidation
The addition is anti–Markownikoff

18. Hydroboration–oxidation
In a substituted cyclic alkene, a trans alcohol is formed.

19. Oxymercuration–demercuration

20. Oxidation of alkenes Test for unsaturation Baeyer’s test
This is also called Hydroxylation
cis-diol

21. Oxidation of alkenes
Cis- hydroxylation

22. Oxidative cleavage of alkenes

23. Oxidation with peroxide

24. Ozonolysis of alkenes

25. Do you know Write IUPAC name of alkene which on ozonolysis gives
one molecule of propanal and one molecule of propanone

26. Addition of methylenes

27. Conjugated dienes (alkadienes)

28. Conjugated dienes (alkadienes)

29. Class exercise

30. Class exercise 1
If singlet carbene is added to the ethylene, the product formed will be
(a) propane (b) butane (c) cyclopropane (d) cyclobutane
Solution:
Cyclopropane
Hence the answer is (c)

31. Class exercise 2
Hydroboration-oxidation of 1-methyl cyclopentane will give
(a) trans-1-methyl cyclopentan-2-ol (b) cis-1-methyl cyclopentan-2-ol (c) Mixture of (a) and (b) (d) 1-methylcyclopentan-1-ol
Solution:
cis-1-methyl cyclopentan-2-ol
Hence the answer is (b)

32. Class exercise 3
Anti-Markownikoff’s addition of HBr is not observed in
(a) But-2-ene (b) Propene (c) But-1-ene (d) Pent-2-ene
Solution:
As but-2-ene is a symmetrical structure, we get same product while anti-Markownikoff’s rule applies.
Hence the answer is (a)

33. Class exercise 4
Electrophilic addition of Br2 to ethylene proceeds through
(a) a transition state (b) a cyclic bromonium ion
Solution:
A three-centred cyclic bromonium ion is formed.
Hence the answer is (a)

34. Class exercise 5
Predict the major product of each of the following reaction.
Solution:

35. Class exercise 6
Predict the major product of each of the following reaction.
Solution:

36. Class exercise 7
Predict the major product of each of the following reaction.
Solution:

37. Class exercise 8 Write a mechanism for each of the following reaction.
Solution:

38. Class exercise 9
A hydrocarbon (R) adds one mole of hydrogen to form n-hexane . When R is oxidized vigorously with hot alk. KMnO4 followed by acid treatment it yields a single carboxylic acid containing carbons. Give the structure of R
Solution:
R: CH3CH2CH = CHCH2CH3

39. Class exercise 10
An organic compound (A) having molecular formula decolourizes bromine water.On hydrogenation (A) yields 2-methylbutane and reductive ozonolysis forms ethanal and propanone. What is A ?
Solution:

40. Thank you