1. Chapter 24From Petroleum to Pharmaceuticals
24.1 Petroleum Refining and the Hydrocarbons
24.2 Functional Groups and Organic Synthesis
24.3 Pesticides and Pharmaceuticals
IR Tutor and Infrared Spectroscopy 1

2. Hydrocarbons
Aliphatic
Aromatic 2

3. Hydrocarbons
Aliphatic
Aromatic
Alkanes
Alkenes
Alkynes 2

4. Alkanes are hydrocarbons in which all of the bonds are single bonds.
Aliphatic C H
Alkanes 2

5. Alkenes are hydrocarbons that contain a carbon-carbon double bond.
Aliphatic C H
Alkenes 2

6. Alkynes are hydrocarbons that contain a carbon-carbon triple bond.
Aliphatic
Alkynes HC CH 2

7. Hydrocarbons
The most common aromatic hydrocarbons are those that contain a benzene ring.
Aromatic H 2

8. Reactive Sites in Hydrocarbons
The Functional Group
Concept 7

9. IR spectroscopic characteristics
Functional Group
a structural unit in a molecule responsible for its characteristic chemical behavior and its
IR spectroscopic characteristics 8

10. functional group is a hydrogen atom the reaction that takes place is
Alkanes
R—H
R—X
functional group is a hydrogen atom
the reaction that takes place is
termed a substitution
one of the hydrogens is substituted by some other atom or group, X 9

11. functional group is a hydrogen
Alkanes
R—H
R—X
functional group is a hydrogen
the reaction that takes place is substitution
one of the hydrogens is substituted by some other atom or group C H C H Cl
+ Cl2
+ HCl 9

12. Functional Groups in Hydrocarbons
alkanes RH
alkenes RH, double bond
alkynes RH, triple bond
aromatics ArH, double bond 10

13. Some Key Functional Groups11

14. Families of organic compounds and their functional groups
Alcohols ROH
Alkyl halides RX (X = F, Cl, Br, I)
Amines primary amine: RNH2
secondary amine: R2NH
tertiary amine: R3N
Ethers ROR 12

15. Many classes of organic compounds contain a carbonyl group
Acyl group 15

16. Many classes of organic compounds contain a carbonyl groupH
Carbonyl group
Aldehyde 15

17. Many classes of organic compounds contain a carbonyl group
Ketone 15

18. Many classes of organic compounds contain a carbonyl groupOH
Carbonyl group
Carboxylic acid 15

19. Many classes of organic compounds contain a carbonyl group
Ester 15

20. Many classes of organic compounds contain a carbonyl group
NH2
Carbonyl group
Amide 15

21. Introduction to Alkanes: Methane, CH4
General formula for an alkane
CnH2n+2
Introduction to Alkanes: Methane, CH4
Ethane, C2H6
Propane, C3H8 21

22. No isomers possible for C1, C2, C3 hydrocarbons
The simplest alkanes
Methane (CH4) CH4
Ethane (C2H6) CH3CH3
Propane (C3H8) CH3CH2CH3
bp -160°C
bp -89°C
bp -42°C
No isomers possible for C1, C2, C3 hydrocarbons 22

23. Isomeric Alkanes: The Butanes
C4H10
General formula for any butane 21

24. C4H10
n-Butane Isobutane
CH3CH2CH2CH3 (CH3)3CH
bp -0.4°C
bp -10.2°C 23

25. Pentane (C5H12) and Beyond
Higher n-Alkanes
Pentane (C5H12) and Beyond
CnH2n+2
n > 4 21

26. CnH2n+2 n > 4 CH3CH2CH2CH2CH3 n-Pentane CH3CH2CH2CH2CH2CH3 n-Hexane
CH3CH2CH2CH2CH2CH2CH3
n-Heptane 24

27. The C5H12 Isomers 21

28. C5H12 CH3CH2CH2CH2CH3 (CH3)2CHCH2CH3 n-Pentane Isopentane (CH3)4C
Neopentane 25

29. How many isomers?
The number of isomeric alkanes increases as the number of carbons increase.
There is no simple way to predict how many isomers there are for a particular molecular formula. 26

30. Table 2.3 Number of Constitutionally Isomeric Alkanes
CH4 1
C2H6 1
C3H8 1
C4H10 2
C5H12 3
C6H14 5
C7H16 9 27

31. Table 2.3 Number of Constitutionally Isomeric Alkanes
CH4 1 C8H18 18
C2H6 1 C9H20 35
C3H8 1 C10H22 75
C4H10 2 C15H32 4,347
C5H12 3 C20H42 366,319
C6H14 5 C40H82 62,491,178,805,831
C7H16 9 27

32. How many isomers with the composition
C6H6 Isomers
How many isomers with the composition
C6H6 can you draw?

33. C6H6 Isomers: How many isomers with the composition C6H6 can you draw?

34. Structure and Bonding in Alkenes11

35. Structure of Ethylene planar bond angles: H-C-H = 117° H-C-C = 121°
bond distances: C—H = 110 pm
C=C = 134 pm
planar 12

36. Each carbon is sp2 hybridized
Bonding in Ethylene s s s s s
Framework of s bonds
Each carbon is sp2 hybridized

37. Each carbon has a half-filled p orbital
Bonding in Ethylene
Each carbon has a half-filled p orbital

38. Side-by-side overlap of half-filled p orbitals gives a p bond
Bonding in Ethylene
Side-by-side overlap of half-filled p orbitals gives a p bond

39. Isomerism in Alkenes 14

40. Isomers are different compounds that have the same molecular formula
(composition). 2

41. Constitutional isomers
Stereoisomers 2

42. Constitutional isomers Stereoisomers
same connectivity;
different arrangement of atoms in space
different connectivity 2

43. Constitutional isomers Stereoisomers
consider the isomeric alkenes of molecular formula C4H8 2

44. C H CH2CH3 C H H3C 1-Butene 2-Methylpropene H CH3 C H3C H3C C CH3 H
cis-2-Butene
trans-2-Butene 16

45. Constitutional isomersH
CH2CH3 C H
H3C
1-Butene
2-Methylpropene H
CH3 C
H3C
Constitutional isomers
cis-2-Butene 16

46. Constitutional isomersH
CH2CH3 C H
H3C
1-Butene
2-Methylpropene
H3C C
CH3 H
Constitutional isomers
trans-2-Butene 16

47. Stereoisomers H
CH3 C
H3C
H3C C
CH3 H
cis-2-Butene
trans-2-Butene 16

48. Molecular Chirality: Enantiomers2

49. A molecule is achiral if its two mirror image forms are superposable.
Chirality
A molecule is chiral if its two mirror image forms are not superposable upon one another.
A molecule is achiral if its two mirror image forms are superposable. 3

50. Cl Br H F It cannot be superposed point for point on its mirror image.
Bromochlorofluoromethane is chiral Cl
It cannot be superposed point for point on its mirror image. Br H F 4

51. Bromochlorofluoromethane is chiralCl Cl Br Br H H F F
To show nonsuperposability, rotate this model 180° around a vertical axis. 4

52. Bromochlorofluoromethane is chiralCl Br Br Cl H H F F 4

53. Another look 6

54. nonsuperposable mirror images are called enantiomers
and
are enantiomers with respect to each other 7

55. Isomers
constitutional
isomers
stereoisomers 8

56. Isomers constitutional isomers stereoisomers enantiomers (optical)
geometric isomers
(cis/trans) 8

57. Chlorodifluoromethane is achiral9

58. Chlorodifluoromethane is achiral
The two structures are mirror images, but are not enantiomers, because they can be superposed on each other. 9

59. Symmetry in Achiral Structures19

60. Symmetry tests for achiral structures
Any molecule with a plane of symmetry must be achiral. 18

61. Plane of symmetry
A plane of symmetry bisects a molecule into two mirror image halves. Chlorodifluoromethane has a plane of symmetry. 21

62. Plane of symmetry
A plane of symmetry bisects a molecule into two mirror image halves. Chlorodifluoromethane has a plane of symmetry. 21

63. Plane of symmetry
A plane of symmetry bisects a molecule into two mirror image halves. 1-Bromo-1-chloro-2-fluoroethene has a plane of symmetry. 21

64. Plane of symmetry
A plane of symmetry bisects a molecule into two mirror image halves. 1-Bromo-1-chloro-2-fluoroethene has a plane of symmetry. 21

65. Physical Properties of Alkanes and Cycloalkanes4

66. increase with increasing number of carbons
Boiling Points
increase with increasing number of carbons
more atoms, more electrons, more opportunities for induced dipole-induced dipole forces
decrease with chain branching
branched molecules are more compact with smaller surface area—fewer points of contact with other molecules 8

68. Boiling Points Heptane bp 98°C Octane bp 125°C Nonane bp 150°C
increase with increasing number of carbons
more atoms, more electrons, more opportunities for induced dipole-induced dipole forces
Heptane bp 98°C
Octane bp 125°C
Nonane bp 150°C 8

69. 2,2,3,3-Tetramethylbutane: bp 107°C
Boiling Points
decrease with chain branching
branched molecules are more compact with smaller surface area—fewer points of contact with other molecules
Octane: bp 125°C
2-Methylheptane: bp 118°C
2,2,3,3-Tetramethylbutane: bp 107°C 8

70. Boiling Points of Alkanes
governed by strength of intermolecular attractive forces
alkanes are nonpolar, so dipole-dipole and dipole-induced dipole forces are absent
only forces of intermolecular attraction are induced dipole-induced dipole forces 6

71. Induced dipole-Induced dipole attractive forces+ – + –
two nonpolar molecules
center of positive charge and center of negative charge coincide in each 5

72. Induced dipole-Induced dipole attractive forces+ – + –
movement of electrons creates an instantaneous dipole in one molecule (left) 5

73. Induced dipole-Induced dipole attractive forces– + + –
temporary dipole in one molecule (left) induces a complementary dipole in other molecule (right) 5

74. Induced dipole-Induced dipole attractive forces– – + +
temporary dipole in one molecule (left) induces a complementary dipole in other molecule (right) 5

75. Induced dipole-Induced dipole attractive forces– – + +
the result is a small attractive force between the two molecules 5

76. Induced dipole-Induced dipole attractive forces– – + +
the result is a small attractive force between the two molecules 5

77. Lots of intermolecular
Straight chain hydrocarbon Branched hydrocarbon
Fewer intermolecular
contacts
Lots of intermolecular
contacts