The document discusses alkenes, focusing on their structure, stability, preparation methods, and various reaction orientations such as Markovnikov, Saytzeff, and Hofmann orientations. It elaborates on the sp2 hybridization, the concept of isomerism, and explains electrophilic addition reactions with an emphasis on carbocation stability and regioselectivity. Additionally, the document covers elimination reactions, including E1 and E2 mechanisms, and factors influencing reactivity.

1. ALKENE
Mr. Amit Z Chaudhari
Dept. of Pharma Chemistry,
L. M. College of Pharmacy,
Ahmedabad - 380009 India
Saytzeffs Hofmann Markownikoff Anti Markownikoff

2. C O N T E N T
Definition
Structure : sp2 hybridization
Isomerism
Stabilities of alkenes
General methods of preparation:
1,2-Elimination
General reactions
Markownikoff’s orientation
Anti Markownikoff’s orientation
Saytzeffs orientation
Hofmann Orientation
Carbocation stability
Regioselectivity
Stereochemical aspects
Electrophilic Addition
Free radicals addition
Hydroboration—oxidation
Ozonalysis
Heat of hydrogenation
Steric repulsion
2

3. D e f i n a t i o n
3
※ Morrison & Boyd ※ Bahl & Bahl ※ Finar Volume 1 ※ Mehta & Mehta ※

4. S T R C T U R E
sp2 hybridization of C
※ Morrison & Boyd ※ Mehta & Mehta ※ Paula Bruice ※ 4

5. S T R C T U R E
sp2 hybridization of C
- sp2 hybrid orbitals – shape
- Each orbital has 33 % s character and 66 % p character.
※ Morrison & Boyd ※ Mehta & Mehta ※ Paula Bruice ※ 5

6. S T R C T U R E
sp2 hybridization of C
Ethene
※ Morrison & Boyd ※ Mehta & Mehta ※ Paula Bruice ※ 6

7. I S O M E R I S M
cis / trans - Geometrical isomerism
- For RCH=CHR
Prostaglandin E2
cis
trans
※ Morrison & Boyd ※ Bahl & Bahl ※ Mehta & Mehta ※ 7

8. S T A B I L I T Y
- Heat of hydrogenation reveals relative stability btwn alkenes.
※ Morrison & Boyd ※ Mehta & Mehta ※ 8

9. S T A B I L I T Y
Heat of hydrogenation and stability: cis- and trans-2-butene.
※ Morrison & Boyd ※ Mehta & Mehta ※ 9

10. S T A B I L I T Y
Comment: trans-isomer is the more stable than cis-isomer in
alkene
cis trans
※ Mehta & Mehta ※ 10

11. S T A B I L I T Y
(2) Relative stability of structural isomers
※ Morrison & Boyd ※ 11

12. S T A B I L I T Y
Conclusion -
※ Morrison & Boyd ※ 12

13. P R E P A R A T I O N S
※ Morrison & Boyd ※ Bahl & Bahl ※ Finar Volume 1 ※ Mehta & Mehta ※ 13

14. P R E P A R A T I O N S
※ Morrison & Boyd ※ Bahl & Bahl ※ Finar Volume 1 ※ Mehta & Mehta ※ Francis A. Carey ※ Paula Bruice 14

15. P R E P A R A T I O N S
Wittig reaction
※ Mehta & Mehta ※ 15

16. ※ Paula Bruice ※
1 , 2 - E L I M I N A T I O N
16

17. 1 , 2 - E L I M I N A T I O N
Intro
Gr. Rxn.
※ Morrison & Boyd ※ Paula Bruice ※ 17

18. 1 , 2 - E L I M I N A T I O N
Kinetics- duality of mechanism
※ Morrison & Boyd ※ Paula Bruice ※ 18

19. 1 , 2 - E L I M I N A T I O N
Kinetics- duality of mechanism
※ Morrison & Boyd ※ Paula Bruice ※ 19

20. 1 , 2 - E L I M I N A T I O N
E2 : mechanism
※ Morrison & Boyd ※ Paula Bruice ※ 20

21. 1 , 2 - E L I M I N A T I O N
E2 : mechanism
※ Morrison & Boyd ※ Paula Bruice ※ 21

22. 1 , 2 - E L I M I N A T I O N
E2 : kinetics
- Single step
※ Morrison & Boyd ※ Paula Bruice ※ 22

23. 1 , 2 - E L I M I N A T I O N
E2 : evidences
※ Morrison & Boyd ※ Paula Bruice ※ 23

24. 1 , 2 - E L I M I N A T I O N
E2 : evidences
(1) follows 2nd order kinetic
※ Morrison & Boyd ※ Paula Bruice ※ 24

25. 1 , 2 - E L I M I N A T I O N
E2 : evidences
(3) show a large H isotope effect
※ Paula Bruice ※ 25

26. 1 , 2 - E L I M I N A T I O N
E2 : evidences
(3) show a large H isotope effect
Experiment performed was,
※ Paula Bruice ※ 26

27. 1 , 2 - E L I M I N A T I O N
E2 : evidences
(3) show a large H isotope effect
Result:
※ Paula Bruice ※ 27

28. 1 , 2 - E L I M I N A T I O N
E2 : evidences
(4) not accompanied by H exchange
※ Morrison & Boyd ※ McMurry ※ D.A. Evans ※ 28

29. 1 , 2 - E L I M I N A T I O N
E2 : evidences
(4) not accompanied by H exchange
※ Morrison & Boyd ※ 29

30. 1 , 2 - E L I M I N A T I O N
E2 : evidences
(4) not accompanied by H exchange
※ Morrison & Boyd ※ 30

31. 1 , 2 - E L I M I N A T I O N
E2 : evidences
(5) Show a large element effect
※ Morrison & Boyd ※ 31

32. 1 , 2 - E L I M I N A T I O N
※ Morrison & Boyd ※
E2 : evidences
(5) Show a large element effect
32

33. 1 , 2 - E L I M I N A T I O N
E2 : Orientation (regioselectivity)
※ Morrison & Boyd ※ Paula Bruice ※ 33

34. 1 , 2 - E L I M I N A T I O N
E2 : Orientation : Saytzeffs orientation
※ Morrison & Boyd ※ Paula Bruice ※ 34

35. 1 , 2 - E L I M I N A T I O N
E2 : Orientation : Saytzeffs orientation
※ Morrison & Boyd ※ Paula Bruice ※ 35

36. 1 , 2 - E L I M I N A T I O N
E2 : Orientation : Saytzeffs orientation
Ease of formation of Alkene is…
※ Morrison & Boyd ※ Paula Bruice ※ 36

37. 1 , 2 - E L I M I N A T I O N
※ Morrison & Boyd ※ Mehta & Mehta ※
Saytzeff pdct Hofmann pdct
E2 :
E2 : Hofmann Orientation / The variable E2 transition state :
37

38. 1 , 2 - E L I M I N A T I O N
※ Morrison & Boyd ※
E2 : Hofmann Orientation / The variable E2 transition state :
※ Morrison & Boyd ※ Francis A. Carey ※ Paula Bruice ※ 38

39. 1 , 2 - E L I M I N A T I O N
E2 : Hofmann Orientation / The variable E2 transition state :
• In El elimination
※ Morrison & Boyd ※ Paula Bruice ※ 39

40. 1 , 2 - E L I M I N A T I O N
※ Morrison & Boyd ※ Paula Bruice ※
E2 : Stereochemistry : have anti-periplanar transition states
※ Morrison & Boyd ※ Paula Bruice ※ Clayden ※ 40

41. 1 , 2 - E L I M I N A T I O N
E2 : Stereochemistry : can be stereoselective
※ Morrison & Boyd ※ Finar Volume 1 ※ Clayden ※ 41

42. 1 , 2 - E L I M I N A T I O N
※ Morrison & Boyd ※ Paula Bruice ※
E2 : Stereochemistry : can be stereospecific
42

43. 1 , 2 - E L I M I N A T I O N
E2 : Stereochemistry : can be stereospecific
※ Morrison & Boyd ※ Clayden ※ 43

44. 1 , 2 - E L I M I N A T I O N
E2 : Order of reactivity of RX
Reactivity study
※ Morrison & Boyd ※ 44

45. 1 , 2 - E L I M I N A T I O N
E2 : Order of reactivity of RX
- Rate ∝ reactivity ,
Probability factor ↑ from 1 o to 3 o
※ Morrison & Boyd ※ 45

46. 1 , 2 - E L I M I N A T I O N
E2 : Order of reactivity of RX
Eact ↓ from mono- to
disubstituted alkene
※ Morrison & Boyd ※ 46

47. 1 , 2 - E L I M I N A T I O N
E1 : mechanism
※ Morrison & Boyd ※ Francis A. Carey ※ Paula Bruice ※ 47

48. 1 , 2 - E L I M I N A T I O N
What will be X & Y axis ?
How many Ts ?
What is in the Ts ?
※ Morrison & Boyd ※ Paula Bruice ※
Potential energy diagram
E1 : mechanism
48

49. 1 , 2 - E L I M I N A T I O N
※ Francis A. Carey ※ Paula Bruice ※
E1 : kinetics
- 2 step mechanism
49

50. 1 , 2 - E L I M I N A T I O N
※ Morrison & Boyd ※ Francis A. Carey ※ Paula Bruice ※
E1 : evidence
50

51. 1 , 2 - E L I M I N A T I O N
E1 : evidence
※ Morrison & Boyd ※ Paula Bruice ※ 51

52. 1 , 2 - E L I M I N A T I O N
E1 : evidence
※ Morrison & Boyd ※ Paula Bruice ※
53
57
52

53. 1 , 2 - E L I M I N A T I O N
E1 : reactivity of RX
※ Morrison & Boyd ※ Paula Bruice ※ 53

54. 1 , 2 - E L I M I N A T I O N
E1 : Orientation
Product ?
Major pdct
82%
※ Morrison & Boyd ※ 54

55. 1 , 2 - E L I M I N A T I O N
E1 : Orientation
※ Morrison & Boyd ※ Paula Bruice ※
Available β-Hs for base ?
Pathway 1
Pathway 2
55

56. 1 , 2 - E L I M I N A T I O N
Progress of reaction
Energy
E1 : Orientation
Reaction coordinate diagram
※ Paula Bruice ※
Pathway 1
Pathway 2
56

57. 1 , 2 - E L I M I N A T I O N
E1 : Rearrangement of carbocations
- E1 reaction mechanism,
※ Morrison & Boyd ※ Paula Bruice ※ 57

58. 1 , 2 - E L I M I N A T I O N
E1 : Rearrangement of carbocations
- Relative stability of carbocation is ,
※ Mehta & Mehta ※ 58

59. 1 , 2 - E L I M I N A T I O N
E1 : Rearrangement of carbocations
- E.g. of rearrangement
※ Morrison & Boyd ※ 59

60. 1 , 2 - E L I M I N A T I O N
E1 : Rearrangement of carbocations
※ Morrison & Boyd ※ 60

61. 1 , 2 - E L I M I N A T I O N
E1 : Rearrangement of carbocations
※ Morrison & Boyd ※ 61

62. 1 , 2 - E L I M I N A T I O N
E1 : Rearrangement of carbocations
- Same way …
… possible in second examples
※ Morrison & Boyd ※ 62

63. 1 , 2 - E L I M I N A T I O N
※ Morrison & Boyd ※ Mehta & Mehta ※
E2 vs. E1
63

64. Factor affecting E reactions :
1 , 2 - E L I M I N A T I O N
※ Morrison & Boyd ※ Solomon ※
E1 :
E2 :
Good Leaving group
most stable C+
Polar solvent
Strong base
more nu. of b- H
most substituted pdct
Good Leaving group
64

65. Factor affecting E reactions :
The substrate structure
- Order of reactivity of RX
1 , 2 - E L I M I N A T I O N
Slide
45
※ Morrison & Boyd ※ Solomon ※
Slide
46
65

66. Factor affecting E reactions :
The Leaving Group
1 , 2 - E L I M I N A T I O N
※ Morrison & Boyd ※ 66

67. Factor affecting E reactions :
The base
※ Clayden ※ Wade ※ Solomon ※
1 , 2 - E L I M I N A T I O N
67

68. Factor affecting E reactions :
Solvents
1 , 2 - E L I M I N A T I O N
※ Wade ※ Solomon ※
68

69. ※ Morrison & Boyd ※ Bahl & Bahl ※ Finar Volume 1 ※ Mehta & Mehta ※ Francis A. Carey ※ Paula Bruice ※
R e a c t i o n s
69

70. ※ Morrison & Boyd ※ Bahl & Bahl ※ Finar Volume 1 ※ Mehta & Mehta ※ Francis A. Carey ※ Paula Bruice ※
R e a c t i o n s
70

71. ※ Morrison & Boyd ※ Bahl & Bahl ※ Finar Volume 1 ※ Mehta & Mehta ※ Francis A. Carey ※ Paula Bruice ※
R e a c t i o n s
71

72. ※ Mehta & Mehta ※
R e a c t i o n s
72

73. E l e c t r o p h i l i c A d d i t i o n
※ Morrison & Boyd ※ Francis A. Carey ※ 73

74. E l e c t r o p h i l i c A d d i t i o n
※ Morrison & Boyd ※ Francis A. Carey ※ 74

75. E l e c t r o p h i l i c A d d i t i o n
※ Morrison & Boyd ※ Francis A. Carey ※ Paula Bruice ※
Mechanism
75

76. E l e c t r o p h i l i c A d d i t i o n
※ Morrison & Boyd ※ Mehta & Mehta ※
Examples
- Addition of sulfuric acid
76

77. E l e c t r o p h i l i c A d d i t i o n
※ Morrison & Boyd ※ Francis A. Carey ※
Examples - regioselectivity
- is Regioselective reaction
77

78. E l e c t r o p h i l i c A d d i t i o n
※ Morrison & Boyd ※ Francis A. Carey ※
Regioselective reaction
a reaction that can produce two (or more) constitutional
isomers but gives one of them in greater amounts than
the other isomers.
Markownikoff’s orientation
- Explain Regioselectivity of the rxn of hydrogen halide with alkene.
78

79. E l e c t r o p h i l i c A d d i t i o n
※ Morrison & Boyd ※ Francis A. Carey ※
Markownikoff’s orientation
Markovnikov's product
79

80. E l e c t r o p h i l i c A d d i t i o n
※ Bahl & Bahl ※ Mehta & Mehta ※ Paula Bruice ※
Markownikoff’s orientation
Stability of Carbocation: 3o > 2o > 1o
Relative stability of 2o C+ favors pathway 1
80

81. E l e c t r o p h i l i c A d d i t i o n
※ Morrison & Boyd ※ Mehta & Mehta ※
Markownikoff’s orientation
81

82. E l e c t r o p h i l i c A d d i t i o n
※ Morrison & Boyd ※
Reactivity of alkenes toward acids
Which intermediate C+
obtained
From these reactants ?
Which reactant react
faster ? depending on
Stability of intermediate C+
82

83. E l e c t r o p h i l i c A d d i t i o n
※ Mehta & Mehta ※ Paula Bruice ※
Examples - rearrangement
83

84. Anti Markownikoff’s orientation
Antimarkovnikov's
product
Markovnikov's product
F r e e R a d i c a l s A d d i t i o n
※ Morrison & Boyd ※ Mehta & Mehta ※ 84

85. F r e e R a d i c a l s A d d i t i o n
Pathway 1
Pathway 2
e- taken up by 2o C follows Pathway 1
※ Mehta & Mehta ※ Francis A. Carey ※
Anti Markownikoff’s orientation
85

86. Anti Markownikoff’s orientation
F r e e R a d i c a l s A d d i t i o n
※ Mehta & Mehta ※ Francis A. Carey ※ 86

87. H y d r o b o r a t i o n — O x i d a t i o n
※ Morrison & Boyd ※ Francis A. Carey ※
Anti Markownikoff’s orientation
87

88. H y d r o b o r a t i o n — O x i d a t i o n
※ Morrison & Boyd ※ Francis A. Carey ※ wade ※ www.chemzipper.com ※
borane-THF complex
88

89. ※ Morrison & Boyd ※ Francis A. Carey ※
Example
H y d r o b o r a t i o n — O x i d a t i o n
89

90. Mechanism
1. Hydroboration of an Alkene
H y d r o b o r a t i o n — O x i d a t i o n
Francis A. Carey ※ Paula Bruice ※ Wade ※ 90

91. Mechanism
1. Hydroboration of an Alkene
H y d r o b o r a t i o n — O x i d a t i o n
Francis A. Carey ※ Paula Bruice ※ Wade ※ 91

92. Mechanism
2. Oxidation of the borane to the alcohol
H y d r o b o r a t i o n — O x i d a t i o n
Francis A. Carey ※ Paula Bruice ※ Wade ※ 92

93. O z o n a l y s i s
※ Morrison & Boyd ※ Finar Volume 1 ※ Mehta & Mehta ※ Clayden ※ www.organic-chemistry.org 93

94. Mechanism
O z o n a l y s i s
※ Paula Bruice ※ Clayden ※ 94

95. Mechanism
O z o n a l y s i s
※ Paula Bruice ※ Clayden ※ 95

96. Examples
O z o n a l y s i s
※ Morrison & Boyd ※ Mehta & Mehta ※ 96

97. A d d i t i o n o f H a l o g e n
※ Morrison & Boyd ※
Anti-addition of bromine to alkene
97

98. A d d i t i o n o f H a l o g e n
※ Morrison & Boyd ※
- Reaction of alkene with bromine can be stereospecific &
stereoselective.
- 2,3-Dibromobutane have 2 chiral centre thus product obtained as 4
isomers , one pair of enantiomers and other pair of mesomers.
98

99. A d d i t i o n o f H a l o g e n
※ Morrison & Boyd ※ 99

100. H a l o h y d r i n f o r m a t i o n
※ Morrison & Boyd ※ 100

101. H a l o h y d r i n f o r m a t i o n
※ Morrison & Boyd ※ 101

102. H a l o h y d r i n f o r m a t i o n
※ Morrison & Boyd ※ Paula Bruice ※ 102

103. F r e e r a d i c a l S u b s t i t u t i o n
Substitution vs addition
※ Morrison & Boyd ※
Besides the addition reactions characteristic of the carbon-carbon double bond,
alkenes may undergo the free-radical substitution characteristic of alkanes.
103

104. F r e e r a d i c a l S u b s t i t u t i o n
※ Morrison & Boyd ※
Substitution vs addition
104

105. F r e e r a d i c a l S u b s t i t u t i o n
Free radical Substitution vs Free radical addition
※ Morrison & Boyd ※ 105

106. F r e e r a d i c a l S u b s t i t u t i o n
※ Morrison & Boyd ※ Clayden ※ chemistrysteps.com/allylic-bromination/ ※
H.C. Brown explanation for this reaction
- Low [ ] of X can be used in stead of high temp. to favors substitution
on allylic C.
106

107. F r e e r a d i c a l S u b s t i t u t i o n
mechanism/ orientation and reactivity
E.g.
※ Morrison & Boyd ※ 107

108. F r e e r a d i c a l S u b s t i t u t i o n
mechanism/ orientation and reactivity
※ Morrison & Boyd ※ 108

109. F r e e r a d i c a l S u b s t i t u t i o n
mechanism/ orientation and reactivity
Vinylic vs allylic H abstraction
※ Morrison & Boyd ※ 109

110. F r e e r a d i c a l S u b s t i t u t i o n
Allylic rearrangement:
Example of free radical substitution reaction in allylic substrate.
obtained with
larger amount
- Here allylic Hs are only present at C3, thus radical formation only
possible at C3 but rearranged product reveals the radical formation
also possible at C1 as bromide radical adds to C1.
※ Morrison & Boyd ※ 110

111. F r e e r a d i c a l S u b s t i t u t i o n
Allylic rearrangement:
Mechanism – Resonance stabilization of allyl radical
Example of free radical substitution reaction in allylic substrate.
This resonance phenomenon in allylic system
is called as Allylic rearrangement.
※ Morrison & Boyd ※ 111

112. of the topic
End
References:
Organic Chemistry – Morrison & boyd
Organic chemistry- Paula Bruice
Organic chemistry- Francis A. Carey
Organic chemistry- Mehta & Mehta