1. Copyright © 2012, The McGraw-Hill Compaies, Inc. Permission required for reproduction or display. Chemistry Third Edition Julia Burdge Lecture PowerPoints Chapter 25 Organic Chemistry

2. CHAPTER 25 Organic Chemistry 2 25.1Why Carbon Is Different 25.2Organic Compounds 25.3Representing Organic Molecules 25.4Isomerism 25.5Organic Reactions 25.6Organic Polymers

3. Topics 25.1Why Carbon Is Different 3 Why Carbon is Different

4. 25.1Why Carbon Is Different Why Carbon is Different 4 Because of its unique nature, carbon is capable of forming millions of different compounds. In nearly all its compounds, carbon forms four covalent bonds, which can be oriented in as many as four different directions:

5. 25.1Why Carbon Is Different Why Carbon is Different 5 Carbon’s small atomic radius allows the atoms to approach one another closely, giving rise to short, strong, carbon-carbon bonds and stable carbon compounds. In addition, carbon atoms that are sp- or sp 2 -hybridized approach one another closely enough for their singly occupied, unhybridized p orbitals to overlap effectively—giving rise to relatively strong bonds.

6. 25.1Why Carbon Is Different Why Carbon is Different 6 Carbon’s valence electrons are in the second shell (n = 2), where there are no d orbitals.

7. 25.1Why Carbon Is Different Why Carbon is Different 7 These attributes enable carbon to form chains (straight, branched, and cyclic) containing single, double, and triple carbon-carbon bonds. Carbon’s formation of chains is called catenation.

8. 25.1Why Carbon Is Different Why Carbon is Different 8 Organic compounds that are related to benzene, or that contain one or more benzene rings, are called aromatic compounds.

9. 25.1Why Carbon Is Different Why Carbon is Different 9 Organic molecules that do not contain the benzene ring are called aliphatic compounds.

10. Topics 25.2Organic Compounds 10 Classes of Organic Compounds Naming Organic Compounds

11. 25.2Organic Compounds Classes of Organic Compounds 11 A variety of different types of organic compounds, each with their own characteristic properties, result from the following: 1.Carbon’s ability to form chains by bonding with itself 2.The presence of elements other than carbon and hydrogen 3.Functional groups 4.Multiple bonds

12. 25.2Organic Compounds Classes of Organic Compounds 12

13. 25.2Organic Compounds Classes of Organic Compounds 13

14. 25.2Organic Compounds Classes of Organic Compounds 14

15. 25.2Organic Compounds Classes of Organic Compounds 15

16. 25.2Organic Compounds 16

17. 25.2Organic Compounds 17

18. 25.2Organic Compounds Classes of Organic Compounds 18

19. 25.2Organic Compounds Classes of Organic Compounds 19

20. 25.2Organic Compounds Classes of Organic Compounds 20

21. 25.2Organic Compounds Classes of Organic Compounds 21

22. 25.2Organic Compounds Naming Organic Compounds 22

23. 25.2Organic Compounds Naming Organic Compounds 23 Alkanes To name substituted alkanes (i.e., those that have substituents): 1.Identify the longest continuous carbon chain to get the parent name. 2.Number the carbons in the continuous chain, beginning at the end closest to the substituent. 3.Identify the substituent and use a number followed by a dash and a prefix to specify its location and identity, respectively.

24. 25.2Organic Compounds Naming Organic Compounds 24 Step 1: The longest continuous carbon chain contains five C atoms.

25. 25.2Organic Compounds Naming Organic Compounds 25 Step 2: Number the carbon atoms beginning at the end nearest the substituent:

26. 25.2Organic Compounds Naming Organic Compounds 26 Step 3: The substituent is a methyl group, CH 3. It is attached to carbon 2. Therefore, the name is 2-methylpentane.

27. SAMPLE PROBLEM 25.1 27 Give names for the following compounds: Setup Solution

28. SAMPLE PROBLEM 25.1 28 Give names for the following compounds:

29. SAMPLE PROBLEM 25.1 29 Setup Solution

30. SAMPLE PROBLEM 25.1 30 Give names for the following compounds: Setup

31. SAMPLE PROBLEM 25.1 31 Solution

32. 25.2Organic Compounds Naming Organic Compounds 32 In molecules that contain two or more identical substituents, the prefixes di, tri, tetra, penta, and so forth, are used to denote the number of substituents.

33. 25.2Organic Compounds Naming Organic Compounds 33 In the case where two or more different substituents are present, the substituent names are alphabetized in the systematic name of the compound. Numbers are used to indicate the positions of the alphabetized substituents. If a prefix is used to denote two or more identical substituents, the prefix is not used to determine the alphabetization—only the substituent name is used.

34. 25.2Organic Compounds Naming Organic Compounds 34

35. 25.2Organic Compounds Naming Organic Compounds 35 Alcohols

36. 25.2Organic Compounds Naming Organic Compounds 36 Carboxylic Acids

37. 25.2Organic Compounds Naming Organic Compounds 37 Esters

38. 25.2Organic Compounds Naming Organic Compounds 38 Aldehydes

39. 25.2Organic Compounds Naming Organic Compounds 39 Ketones

40. 25.2Organic Compounds Naming Organic Compounds 40 Primary Amines

41. 25.2Organic Compounds Naming Organic Compounds 41 Primary Amides

42. 25.2Organic Compounds Naming Organic Compounds 42 Many compounds contain more than one functional group. An amino acid, for example, contains both the amine group and the carboxy group.

43. SAMPLE PROBLEM 25.2 43 Identify the functional group(s) in each molecule:

44. SAMPLE PROBLEM 25.2 44 Solution

45. SAMPLE PROBLEM 25.2 45 Identify the functional group(s) in each molecule:

46. SAMPLE PROBLEM 25.2 46 Solution

47. SAMPLE PROBLEM 25.2 47 Identify the functional group(s) in each molecule:

48. SAMPLE PROBLEM 25.2 48 Solution

49. Topics 25.3Representing Organic Molecules 49 Condensed Structural Formulas Kekulé Structures Skeletal Structures Resonance

50. 25.3Representing Organic Molecules Condensed Structural Formulas 50 A condensed structural formula, or simply a condensed structure, shows the same information as a structural formula, but in a condensed form.

51. 25.3Representing Organic Molecules Condensed Structural Formulas 51

52. 25.3Representing Organic Molecules Kekulé Structures 52 Kekulé structures are similar to Lewis structures except that they do not show lone pairs.

53. 25.3Representing Organic Molecules Skeletal Structures 53 A skeletal structure consists of straight lines that represent carbon-carbon bonds. The carbon atoms themselves (and the attached hydrogen atoms) are not shown, but you need to know that they are there.

54. 25.3Representing Organic Molecules Skeletal Structures 54

55. 25.3Representing Organic Molecules Skeletal Structures 55

56. SAMPLE PROBLEM 25.3 56 Write a molecular formula and a structural formula (or condensed structural formula) for the following: Setup

57. SAMPLE PROBLEM 25.3 57 Solution

58. 25.3Representing Organic Molecules Resonance 58 Two or more equally valid Lewis structures that differ only in the position of their electrons are called resonance structures. The concept of resonance allows us to envision certain electron pairs as delocalized over several atoms.

59. 25.3Representing Organic Molecules Resonance 59 Delocalization of electron pairs imparts additional stability to a molecule, and a species that can be represented by two or more resonance structures is said to be resonance stabilized. versus

60. SAMPLE PROBLEM 25.4 60 Draw all the possible resonance structures for the hydrogen phosphate ion (HPO 4 2– ). Use curved arrows to indicate how electrons are repositioned, and determine the position(s) of the negative charges. Setup

61. SAMPLE PROBLEM 25.4 61 Solution

62. Topics 25.4Isomerism 62 Constitutional Isomerism Stereoisomerism

63. 25.4Isomerism Constitutional Isomerism 63 Also known as structural isomerism, constitutional isomerism occurs when the same atoms can be connected in two or more different ways.

64. 25.4Isomerism Constitutional Isomerism 64

65. 25.4Isomerism Stereoisomerism 65 Stereoisomers are those that contain identical bonds but differ in the orientation of those bonds in space. Two types of stereoisomers exist: geometrical isomers and optical isomers. Geometrical isomers occur in compounds that have restricted rotation around a bond. Stereoisomers that are mirror images of each other, but are not superimposable, are called optical isomers.

66. 25.4Isomerism Stereoisomerism 66

67. 25.4Isomerism Stereoisomerism 67

68. 25.4Isomerism Stereoisomerism 68 Molecules with nonsuperimposable mirror images are called chiral; and a pair of such mirror-image molecules are called enantiomers.

69. 25.4Isomerism Stereoisomerism 69 it often is necessary to represent tetrahedral molecules (three- dimensional objects) on paper (a two-dimensional surface). This is done using dashes to represent bonds that point behind the page, and wedges to represent bonds that point in front of the page.

70. 25.4Isomerism Stereoisomerism 70 One property of chiral molecules is that the two enantiomers rotate the plane of plane-polarized light in opposite directions; that is, they are optically active. If the plane of polarization is rotated to the right, the isomer is said to be dextrorotatory and is labeled d; if it is rotated to the left, the isomer is called levorotatory and labeled l. Enantiomers always rotate the light by the same amount, but in opposite directions. Thus, in an equimolar mixture of both enantiomers, called a racemic mixture, the net rotation is zero.

71. 25.4Isomerism Stereoisomerism 71

72. Topics 25.5Organic Reactions 72 Addition Reactions Substitution Reactions Other Types of Organic Reactions

73. 25.5Organic Reactions Addition Reactions 73 An electrophile is a species with a positive or partial positive charge. An electrophile is attracted to a region of negative or partial negative charge. Electrophiles are electron-poor.

74. 25.5Organic Reactions Addition Reactions 74 A nucleophile is a species with a negative or partial negative charge. A nucleophile is attracted to a region of positive or partial positive charge (i.e., an electrophile). Nucleophiles are electron-rich. Electron-rich sites and electron-poor sites are attracted to one another.

75. 25.5Organic Reactions Addition Reactions 75

76. 25.5Organic Reactions Addition Reactions 76

77. 25.5Organic Reactions Addition Reactions 77

78. 25.5Organic Reactions Addition Reactions 78 The overall reaction is called an addition reaction. Specifically, this is an electrophilic addition reaction because it begins with the electrophilic attack by HCl on the region of electron density in the double bond.

79. 25.5Organic Reactions Addition Reactions 79 Addition reactions can also begin with nucleophilic attack, in which case the reaction is called a nucleophilic addition. In a nucleophilic addition reaction, a bond forms when a nucleophile donates a pair of electrons to an electron- deficient atom.

80. 25.5Organic Reactions Addition Reactions 80

81. 25.5Organic Reactions Substitution Reactions 81 Electrophilic and nucleophilic attack can also lead to substitution reactions in which one group is replaced by another group. Electrophilic substitution occurs when an electrophile attacks an aromatic molecule and replaces a hydrogen atom. Nucleophilic substitution occurs when a nucleophile replaces another group on a carbon atom.

82. 25.5Organic Reactions Substitution Reactions 82

83. 25.5Organic Reactions Substitution Reactions 83

84. 25.5Organic Reactions Substitution Reactions 84

85. 25.5Organic Reactions Substitution Reactions 85

86. 25.5Organic Reactions Substitution Reactions 86

87. SAMPLE PROBLEM 25.5 87 Using curved arrows to indicate the movement of electrons, draw the mechanism for each of the following reactions: (a)nucleophilic addition of CN – to CH 3 CHO and (b)electrophilic substitution of benzene with + SO 3 H. (Draw all resonance structures for the carbocation intermediate.)

88. SAMPLE PROBLEM 25.5 88 Solution

89. SAMPLE PROBLEM 25.5 89 Solution

90. 25.5Organic Reactions Other Types of Organic Reactions 90 An elimination reaction is one in which a double bond forms and a molecule such as water is removed.

91. 25.5Organic Reactions Other Types of Organic Reactions 91 When a molecule gains O or loses H, it is oxidized. When a molecule loses O or gains H, it is reduced.

92. 25.5Organic Reactions Other Types of Organic Reactions 92 Isomerization reactions are those in which one isomer is converted to another.

93. Topics 25.6Organic Polymers 93 Addition Polymers Condensation Polymers Biological Polymers

94. 25.6Organic Polymers Addition Polymers 94 Polymers are molecular compounds, either natural or synthetic, that are made up of many repeating units called monomers. Addition polymers form when monomers such as ethylene join end to end to make polyethylene. Reactions of this type can be initiated by a radical—a species that contains an unpaired electron.

95. 25.6Organic Polymers Addition Polymers 95

96. 25.6Organic Polymers Addition Polymers 96

97. 25.6Organic Polymers 97

98. 25.6Organic Polymers Condensation Polymers 98 Reactions in which two or more molecules become connected with the elimination of a small molecule, often water, are called condensation reactions.

99. 25.6Organic Polymers Condensation Polymers 99 Condensation polymers form when molecules with two different functional groups combine, with the elimination of a small molecule, often water. Many condensation polymers are copolymers, meaning that they are made up of two or more different monomers.

100. 25.6Organic Polymers Condensation Polymers 100

101. 25.6Organic Polymers Biological Polymers 101 Naturally occurring polymers include proteins, polysaccharides, and nucleic acids. Proteins, polymers of amino acids, play an important role in nearly all biological processes. The bonds that form between amino acids are called peptide bonds. Very long chains of amino acids assembled in this way are called proteins, while shorter chains are called polypeptides.

102. 25.6Organic Polymers Biological Polymers 102

103. 25.6Organic Polymers 103

104. 25.6Organic Polymers 104

105. 25.6Organic Polymers 105

106. 25.6Organic Polymers 106

107. 25.6Organic Polymers 107

108. 25.6Organic Polymers 108

109. 25.6Organic Polymers Biological Polymers 109 Polysaccharides are polymers of sugars such as glucose and fructose.

110. 25.6Organic Polymers Biological Polymers 110

111. 25.6Organic Polymers Biological Polymers 111 Nucleic acids, which are polymers of nucleotides, play an important role in protein synthesis. There are two types of nucleic acids: deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). Each nucleotide in a nucleic acid consists of a purine or pyrimidine base, a furanose sugar (deoxyribose for DNA; ribose for RNA), and a phosphate group.

112. 25.6Organic Polymers 112

113. 25.6Organic Polymers 113