1. Unit 3: Reactions of Alkenes. Thermodynamics and Kinetics
Hydrocarbons that contain only
C-C bond are called alkanes
Hydrocarbons that contain C=C bond are called alkenes or olefins (oil forming)

2. 尤加利樹油

3. 3.1 Molecular Formula and the Degree of Unsaturation
Alkane
CH3(CH2)nCH3
CnH2n+2
Alkene
CH3(CH2)nCH3
CnH2n
Cyclic alkane
CnH2n
Cyclic alkene
CnH2n-2
Degree of unsaturation = 2
1 p bond or 1 ring, degree of unsaturation = 1

5. 3.3 The Structure of Alkenes

6. 3.4 cis-trans Isomerism Rotational barrier 63kcal/mol
H3C—CH3 rotational barrier = 2.9 kcal/mol

8. Cis-Trans Interconversion in Vision

9. cis-trans Isomerism
2004/2/21 end

10. 3.6 Reactivity Considerations
Functional group

11. Organic Reactions
Electron-rich atoms or molecules are attracted to electron-deficient atoms or molecules
Nucleophile: an electron-rich atom or molecule
Electrophile: an electron-deficient atom or molecule
A nucleophile and an electrophile react with each other

12. Electrophiles and Nucleophiles

13. `

14. Mechanism of the Reaction

15. 2002/10/11 end

16. 3.7 Thermodynamics and Kinetics
Reaction coordinate digram
2002/10/18

17. Thermodynamics Describes the properties of a system at equilibrium
The more stable the compound,
the greater its concentration at equilibrium

19. Gibbs standard free energy change
This symbol indicates that the reaction takes place under standard conditions
--all species at 1 M, 25 OC, and 1 atm. ↓
R is the gas constant (1.986 cal/mol OK)
T is the absolute temperature (OK)

21. Free Energy, Enthalpy and Entropy
DHO < 0, exothermic reaction; DHO > 0, endothermic reaction
In condensed phase, DSO ≈ 0. Therefore DGO ≈ DHO

22. Calculate DHO for a Certain Reaction

23. p.130

24. Solvation: the interaction between a solvent and a molecule (or ion) in solution
Solvation can have a large effect on the DHO of a reaction,
and it can also affect the DSO of a reaction.

25. Kinetics Deals with the rates of chemical reactions and the factors
that affect those rates
Free energy of activation

28. Rate Law First-order reaction Second-order reaction

29. The Arrhenius equation:

30. Rate Constant and Equilibrium Constant
At equlibrium, forward rate = reverse rate.
k1 [A] = k-1 [B]
therefore

32. Reaction Coordinate Diagram for the Addition of HBr to 2-Butene
Bonds being broken
p DH = 61 kcal/mol
H-Br DH = 87 kcal/mol
DHtotal = 148 kcal/mol
Bonds being formed C-H DH = 101 kcal/mol
Bonds being formed C-Br DH = 69 kcal/mol
Total DH change = +47 kcal/mol
Over all DH change = -22 kcal/mol

33. Reaction Coordinate Diagram for the Addition of HBr to 2-Butene
-22 kcal/mol

34. 3.8 General Mechanism for Electrophilic Addition

35. 3.9 Addition of Hydrogen Halides

37. Relative Stabilities of Carbocations

39. sp3
sp2
Inductive effect

40. Relative Stabilities of Carbocations

41. 3.11 The Structure of the Transition State

42. The Hammond postulate

43. 2002/10/18 end expected

44. 3.12 Regioselectivity of Electrophilic Addition Reactions

45. Constitutional isomers
Major product
Minor product
Major product
Minor product
Regioselective reaction
Non-regioselective reaction

47. 3.13 Addition of Water and Alcohols
hydration

49. Addition of Alcohol to Alkene

50. 3.14 Rearrangement of Carbocations
According Markovnikov’ rule
This compound should be major product

51. Mechanism for the Formation of Rearranged Product
a tertiary carbocation
a secondary carbocation
attack on
rearranged
carbocation
attack on
unrearranged
carbocation
minor product
major product

52. Mechanism for the Formation of Rearranged Product
a tertiary carbocation
a secondary carbocation
attack on
rearranged
carbocation
attack on
unrearranged
carbocation
major product
minor product

53. Carbocation rearrangements also can occur by ring expansion
1,2-alkyl shift

54. 3.15 Addition of Halogens
p.154 last sentence

55. F2 reacts explosively with alkenes!!!
unstable
F2 reacts explosively with alkenes!!!

56. Formation of Halohydrins

59. 3.18 Addition of Radicals. The Relative Stabilities of Radicals

61. Radical addition reaction
March 6,2004

63. Addition of HBr through Radical Mechanism

64. Addition of HBr through Radical Mechanism

67. 3.19 Addition of Hydrogen. The Relative Stabilities of Alkenes

69. Heat of Hydrogenation

70. Relative Stabilities of Alkenes