1. Chapter 20 Organic Chemistry
Lecture Presentation
Chapter 20 Organic Chemistry
Sherril Soman
Grand Valley State University

2. Fragrances and Odors
Our sense of smell helps us identify food, people, and other organisms, and alerts us to dangers such as polluted air or spoiled food.
Odorants must be volatile.
However, many volatile substances have no scent at all.
Most common smells are caused by organic molecules.
The study of compounds containing carbon combined with one or more of the elements hydrogen, nitrogen, oxygen, and sulfur, including their properties and their reactions, is known as organic chemistry.

4. What Is Organic Chemistry?
Organic chemistry is a branch of chemistry that focuses on compounds that contain carbon.
Except CO, CO2, carbonates, and carbides
Even though organic compounds only contain a few elements, the unique ways carbon atoms can attach together to form molecules leads to millions of different organic compounds.

5. The Chemistry of Life
Life as we know it is because of organic chemistry.
Organic molecules can be very large and complex.
It is this complexity of large organic molecules that allows the complex functions of the cells to occur.

6. Differences Between Organic and Inorganic Compounds
Organic compounds are easily decomposed into simpler substances by heating, but inorganic substances are not.
Inorganic compounds were readily synthesized in the lab, but synthesis of organic compounds in the lab is hard.

7. What’s Special About Organic Compounds?
Organic compounds tend to be molecular.
They are mainly composed of just six nonmetallic elements.
C, H, O, N, S, and P
Compounds are found in all three states.
Solids, liquids, and gases
Solids tend to have low melting points
Solubility in water varies depending on which of the other elements are attached to C and how many there are.
CH3OH is miscible with water; C10H21OH is insoluble.

8. What’s So Special About Carbon?
Carbon atoms can do some unique things that other atoms cannot.
Carbon can bond to as many as four other atoms.
Bonds to carbon are very strong and nonreactive.

9. What’s So Special About Carbon?
Carbon atoms can attach together in long chains.
Carbon atoms can attach together to form rings.
Carbon atoms can form single, double, or triple bonds.

10. Hydrocarbons contain only C and H. Insoluble in water
Aliphatic or aromatic
Insoluble in water
No polar bonds to attract water molecules
Aliphatic hydrocarbons
Saturated or unsaturated aliphatics
Saturated = alkanes; unsaturated = alkenes or alkynes
May be chains or rings
Chains may be straight or branched.
Aromatic hydrocarbons

13. Formulas
Molecular formulas show the kinds of atoms in the molecule, but they do not show how they are attached.
Structural formulas show you the attachment pattern in the molecule.
Models not only show you the attachment pattern, but give you an idea about the shape of the molecule.

14. Condensed Structural Formulas
Attached atoms listed in order
Central atom with attached atoms
Follow normal bonding patterns
Use to determine position of multiple bonds
() used to indicate more than one identical group attached to same previous central atom
Unless () group is listed first, in which case attached to next central atom

15. Uses of Hydrocarbons

16. Uses of Hydrocarbons

17. Uses of Hydrocarbons

18. Physical Properties of Aliphatic Hydrocarbons
Boiling points and melting points increase as the size of the molecule increases.
Nonpolar molecules
Main attractive forces are dispersion forces
Less dense than water
Insoluble in water

19. Saturated Hydrocarbons
A saturated hydrocarbon has all C─C single bonds.
It is saturated with hydrogens.
Saturated aliphatic hydrocarbons are called alkanes.
Chain alkanes have the general formula CnH2n+2.
Ring alkanes have all C─C single bonds, but have fewer hydrogens than a chain with the same number of carbons.

20. Unsaturated Hydrocarbons
Unsaturated hydrocarbons have one or more C═C double bonds or C≡C triple bonds.
Unsaturated aliphatic hydrocarbons that contain C═C are called alkenes.
The general formula of a monounsaturated chain alkene is CnH2n.
Remove two more H for each additional double bond.
Unsaturated aliphatic hydrocarbons that contain C≡C are called alkynes.
The general formula of an alkyne with one triple bond is CnH2n−2.
Remove four more H for each additional triple bond.

21. Aromatic Hydrocarbons
Aromatic hydrocarbons contain a ring structure that seems to have C═C, but doesn’t behave that way.
The most prevalent example is benzene.
C6H6
Other compounds have the benzene ring with other groups substituted for some of the hydrogens.

22. Carbon Skeleton Formulas
Each angle, and beginning and end, represent a C atom.
H omitted on C
Included on functional groups
Multiple bonds indicated
Double line is double bond; triple line is triple bond

23. Formulas

24. Isomers are different molecules with the same molecular formula.
Isomerism
Isomers are different molecules with the same molecular formula.
Structural isomers are isomers that have a different pattern of atom attachment.
Also known as constitutional isomers
Stereoisomers are isomers with the same pattern of atom attachments, but the atoms have a different spatial orientation.

25. Structural Isomers of C4H10
Butane, BP = 0 °C
Isobutane, BP = −12 °C

26. Rotation about a Bond Is Not Isomerism

27. Possible Structural Isomers

28. Stereoisomers
Stereoisomers are different molecules whose atoms are connected in the same order, but with a different spatial direction.
Optical isomers are stereoisomers that are nonsuperimposable mirror images of each other.
Geometric isomers are stereoisomers that are not optical isomers.

29. Nonsuperimposable Mirror Images
The mirror image cannot be rotated so all its atoms align with the same atoms of the original molecule.

30. Chirality
Any molecule with a nonsuperimposable mirror image is said to be chiral.
Any carbon with four different substituents will be a chiral center.
A pair of nonsuperimposable mirror images are called a pair of enantiomers.

31. Optical Isomers of 3-Methylhexane

32. Plane Polarized Light
Light that has been filtered so that only those waves traveling in a single plane are allowed through

33. Optical Activity
Enantiomers have all the same physical properties except one—the direction they rotate the plane of plane-polarized light
Each one of the enantiomers will rotate the plane the same amount, but in opposite directions.
Dextrorotatory = rotates the plane to the right
Levorotatory = rotates the plane to the left

34. Mixtures of Enantiomers
An equimolar mixture of a pair of enantiomers is called a racemic mixture.
Because half the molecules are rotating the plane to the left and the other half are rotating it to the right, the rotations cancel, and the racemic mixture does not rotate the plane.
If the mixture is nonracemic, the amount of rotation can be used to determine the percentages of each enantiomer in the mixture.

35. Chemical Behavior of Enantiomers
A pair of enantiomers will have the same chemical reactivity in a nonchiral environment.
But in a chiral environment they may exhibit different behaviors.
Enzyme selection of one enantiomer of a pair

36. General formula CnH2n+2 for chains Very unreactive
Alkanes
Also know as paraffins
Aliphatic
General formula CnH2n+2 for chains
Very unreactive
Come in chains or/and rings
CH3 groups at ends of chains, CH2 groups in the middle
Saturated
Branched or unbranched

39. Physical Properties of n–Alkanes

40. Each name consists of three parts
Naming
Each name consists of three parts
Prefix
Indicates position, number, and type of branches
Indicates position, number, and type of each functional group
Parent
Indicates the length of the longest carbon chain or ring
Suffix
Indicates the type of hydrocarbon
-ane, -ene, -yne
Certain functional groups

41. Naming Alkanes 1. Find the longest continuous carbon chain.
2. Number the chain from end closest to a branch.
If first branches are equal distance, use next substituent
3. Name branches as alkyl groups.
Locate each branch by preceding its name with the carbon number on the chain.
4. List branches alphabetically.
Do not count n-, sec-, t-, count iso
5. Use prefix if more than one of same group present.
“Di-,” “tri-,” “tetra-,” “penta-,” “hexa-”
Do not count in alphabetizing

42. Prefixes

43. Alkyl Groups

44. Aliphatic, unsaturated Formula for one double bond = CnH2n.
Alkenes
Also known as olefins
Aliphatic, unsaturated
C═C double bonds
Formula for one double bond = CnH2n.
Subtract 2 H from alkane for each double bond.
Trigonal shape around C
Flat
Polyunsaturated = many double bonds

45. Alkenes ethene = ethylene propene = propylene H H C C3
Produced by ripening fruit
Used to make polypropylene
Used to make polyethylene

47. Physical Properties of Alkenes
Pi bond electrons not held as tight as sigma; therefore, alkenes are more polarizable than alkanes.
Cis generally more polar than trans
Trans lower boiling point
More carbon groups attached to the double bond = higher boiling point.
For equal numbers of C
Densities similar to alkanes
Trans higher melting point than cis
Molecules are more symmetrical and pack better.

48. Also known as acetylenes Aliphatic, unsaturated CºC triple bond
Alkynes
Also known as acetylenes
Aliphatic, unsaturated
CºC triple bond
Formula for one triple bond = CnH2n − 2.
Subtract 4 H from alkane for each triple bond.
Linear shape
Internal alkynes have both triple bond carbons attached to C.
Terminal alkynes have one carbon attached to H.

50. Alkynes
Ethyne = acetylene
Used in welding torches

51. Physical Properties of Alkynes
Higher boiling points than similar sized alkenes
Similar size = same number of carbons
More pi bond = more polarization = higher boiling point
Slightly higher densities than similar alkenes
There are no alkyne cis or trans isomers.
Internal alkynes have higher boiling points than terminal alkynes.
With the same number of C

52. Naming Alkenes and Alkynes
Change suffix on main name from -ane to -ene for base name of alkene, or to -yne for the base name of the alkyne.
Number chain from end closest to multiple bond.
Number in front of main name indicates first carbon of multiple bond.

53. This is often called cis–trans isomerism.
Geometric Isomerism
Because the rotation around a double bond is highly restricted, you will have different molecules if groups have different spatial orientation about the double bond.
Stereoisomers
This is often called cis–trans isomerism.
When groups on the doubly bonded carbons are cis, they are on the same side of the double bond.
When groups on the doubly bonded carbons are trans, they are on opposite sides.

54. Cis–Trans Isomerism

56. Reactions of Hydrocarbons
All hydrocarbons undergo combustion.
Combustion is always exothermic.
About 90% of U.S. energy generated by combustion
CH3CH2CH3(g) + 5 O2(g) → 3 CO2(g) + 4 H2O(g)
CH2═CHCH2CH3(g) + 6 O2(g) → 4 CO2(g) + 4 H2O(g)
CH≡CCH3(g) + 4 O2(g) → 3 CO2(g) + 2 H2O(g)

57. Burning hydrocarbons releases heat and light energy.
Chemical Energy
Burning hydrocarbons releases heat and light energy.
Combustion
Alkane + oxygen ® carbon dioxide + water
Larger alkane, more heat released

58. Alkane Reactions Substitution To start breaking bonds
Replace H with a halogen atom.
Initiated by addition of energy in the form of heat or ultraviolet light
To start breaking bonds
Generally get multiple products with multiple substitutions
Methane + chlorine  chloromethane + HCl

59. Alkene and Alkyne Reactions: Addition
Adding a molecule across the multiple bond
Hydrogenation = adding H2
Converts unsaturated molecule to saturated
Alkene or alkyne + H2 → alkane
Generally requires a catalyst
Halogenation = adding X2
Hydrohalogenation = adding HX
HX is polar.
When adding a polar reagent to a double or triple bond, the positive part attaches to the carbon with the most H’s.

60. Addition Reactions

61. Aromatic Hydrocarbons
Contain benzene ring structure
Even though they are often drawn with C═C, they do not behave like alkenes.

62. Resonance Hybrid
The true structure of benzene is a resonance hybrid of two structures.

63. Naming Monosubstituted Benzene Derivatives
(Name of substituent)benzene
Halogen substituent = change ending to “o”
Or name of a common derivative

64. Naming Benzene as a Substituent
When the benzene ring is not the base name, it is called a phenyl group.

65. Naming Disubstituted: Benzene Derivatives
Number the ring starting at attachment for first substituent, and then move toward the second.
Order substituents alphabetically.
Use “di-” if both substituents are the same.

66. Naming Disubstituted: Benzene Derivatives
Alternatively, use relative position prefix.
Ortho- = 1,2; meta- = 1,3; para- = 1,4
2-chlorotoluene
ortho-chlorotoluene
o-chlorotoluene
3-chlorotoluene
meta-chlorotoluene
m-chlorotoluene
4-chlorotoluene
para-chlorotoluene
p-chlorotoluene

67. Polycyclic Aromatic Hydrocarbons
Contain multiple benzene rings fused together
Fusing = sharing a common bond

68. Functional Groups
Other organic compounds are hydrocarbons in which functional groups have been substituted for hydrogens.
A functional group is a group of atoms that shows a characteristic influence on the properties of the molecule.
Generally, the reactions that a compound will perform are determined by what functional groups it has.
Because the kind of hydrocarbon chain is irrelevant to the reactions, it may be indicated by the general symbol.

70. Isopropyl alcohol = (CH3)2CHOH
Alcohols
R—OH
Ethanol = CH3CH2OH
Grain alcohol = fermentation of sugars in grains
Alcoholic beverages
Proof number = 2 times percentage of alcohol
Gasohol
Isopropyl alcohol = (CH3)2CHOH
2-propanol
Rubbing alcohol
Poisonous
Methanol = CH3OH
Wood alcohol = thermolysis of wood
Paint solvent

71. Naming Alcohols
Main chain contains OH.
Number main chain from end closest to OH.
Give base name -ol ending and place number of C on chain where OH attached in front.
Name as hydroxy group if higher precedence group present.

72. Nucleophilic substitution CH3─OH + HCl ® CH3Cl + H2O
Reactions of Alcohols
Nucleophilic substitution
CH3─OH HCl ® CH3Cl + H2O
Acid catalyzed elimination (dehydration)
CH3─ CH2OH ® CH2═CH H2O
H2SO4

73. Alcohols with very active metals
Reactions of Alcohols
Oxidation
CH3CH2OH ® CH3CHO ® CH3COOH
−2 H
A common oxidizing agent is Na2Cr2O7.
Alcohols with very active metals
2 CH3─OH K ® 2 CH3O−K H2

75. Contain the carbonyl group
Aldehydes and Ketones
Contain the carbonyl group
Aldehydes = at least 1 side H
Ketones = both sides R groups
Many aldehydes and ketones have pleasant tastes and aromas.
Some are pheromones.
Formaldehyde = H2C=O
Pungent gas
Formalin = a preservative
Wood smoke, carcinogenic
Acetone = CH3C(=O)CH3
Nail-polish remover

78. Ketone Odors and Flavors
Acetophenone = pistachio
Carvone = spearmint
Ionone = raspberries
Muscone = musk

79. Naming Aldehydes and Ketones
Main chain contains C═O.
Unless COOH present
Number main chain from end closest to C═O.
For aldehydes, give base name -al ending.
Always on C1
For ketones, give base name -one ending and place number of C on chain where C═O attached in front. 79

80. Reactions
Aldehydes and ketones are generally synthesized by the oxidation of alcohols.
Therefore, reduction of an aldehyde or ketone results in an alcohol.
Common reducing agents are H2 with a Ni catalyst, NaBH4, and LiAlH4.

81. Therefore, reduction of an aldehyde or ketone results in an alcohol.
Reactions
Aldehydes and ketones are generally synthesized by the oxidation of alcohols.
Therefore, reduction of an aldehyde or ketone results in an alcohol.
Common reducing agents are H2 with a Ni catalyst, NaBH4, and LiAlH4. 81

82. Therefore, reduction of an aldehyde or ketone results in an alcohol.
Reactions
Aldehydes and ketones are generally synthesized by the oxidation of alcohols.
Therefore, reduction of an aldehyde or ketone results in an alcohol.
Common reducing agents are H2 with a Ni catalyst, NaBH4, and LiAlH4. 82

83. Carbonyl Group C═O group is highly polar.
Many reactions involve addition across C═O,
with positive part attached to O.

84. Addition to C═O
Polar molecules add across the C═O, with the positive part attaching to O. d+ d−

85. Ethanoic acid = acetic acid Methanoic acid = formic acid
Carboxylic Acids
RCOOH
Sour tasting
Weak acids
Citric acid
Found in citrus fruit
Ethanoic acid = acetic acid
Vinegar
Methanoic acid = formic acid
Insect bites and stings

86. Synthesis of Carboxylic Acids
Made by the oxidation of aldehydes and alcohols.

87. Naming Carboxylic Acids
Carboxylic acid group always on end of main chain
Has highest naming precedence of functional groups
C of group always C1
Position not indicated in name
Change ending to -oic acid

88. Examples of Naming Carboxylic Acids

90. RaCOOH + RbOH ⇔ RaCOORb + H2O
Esters
R—COO—R
Sweet odor
Made by reacting carboxylic acid with an alcohol
RaCOOH + RbOH ⇔ RaCOORb + H2O

91. Carboxylic acid group always on end of main chain
Naming Esters
Carboxylic acid group always on end of main chain
Unless carboxylic acid group present
C of ester group on C1
Position not indicated in name
Begin name with alkyl group attached to O.
Name main chain with -oate ending.

92. Condensation Reactions
A condensation reaction is any organic reaction driven by the removal of a small molecule, such as water.
Esters are made by the condensation reaction between a carboxylic acid and an alcohol.
The reaction is acid catalyzed.

93. Condensation Reactions
A condensation reaction is any organic reaction driven by the removal of a small molecule, such as water.

94. Condensation Reactions
A condensation reaction is any organic reaction driven by the removal of a small molecule, such as water.
Acid anhydrides are made by the condensation reaction between to carboxylic acid molecules.
The reaction is driven by heat. 94

95. Synthesis of Aspirin (Acetylsalicylic Acid)

96. Ethers
Ethers have the general formula ROR.
The two R groups may be different or identical.

97. Ethers
Diethyl ether is the most common ether.
It is useful as a laboratory solvent and can dissolve many organic compounds.
It has a low boiling point.

98. Amines
N containing organic molecules
Very bad smelling
Form when proteins decompose
Organic bases
Name alkyl groups attached to the N, then add -amine to the end.

99. Many amines are biologically active.
Dopamine – a neurotransmitter
Epinephrine – an adrenal hormone
Pyridoxine – vitamin B6
Alkaloids are plant products that are alkaline and biologically active.
Toxic
Coniine from hemlock
Cocaine from coca leaves
Nicotine from tobacco leaves
Mescaline from peyote cactus
Morphine from opium poppies

100. RCOOH + H—NHR‘⇔ RCONHR’ + H2O
Amine Reactions
Weak bases
React with strong acids to form ammonium salts
RNH2 + HCl → RNH3+Cl−
React with carboxylic acids in a condensation reaction to form amides
RCOOH + H—NHR‘⇔ RCONHR’ + H2O

101. Polymers
Polymers are very large molecules made by repeated linking together of small molecules.
Monomers

102. Polymers
Natural polymers are polymers found in both the living and nonliving environment.
Modified natural polymers are natural polymers that have been chemically altered.
Synthetic polymers are polymers made in a lab from one, two, or three small molecules linked in a repeating pattern.
Plastics, elastomers (rubber), fabrics, adhesives
Composites are materials made of polymers mixed with various additives.
Additives such as graphite, glass, metallic flakes

103. Natural Polymers
Polysaccharides – polymers made of repeating small sugar molecule units
Cellulose (cotton)
Starch
Proteins – polymers made of repeating amino acid units
Nucleic acids (DNA) – polymers made of repeating nucleotide units
Natural latex rubber – polyisoprene
Shellac – a resin secreted by lac bugs
Gutta-percha – a polyisoprene latex from the sap of the gutta-percha plant
Used to fill space for root canal
Amber, lignin, pine rosin – resins from trees
Asphalt – polymeric petroleum

105. Modified Natural Polymers
Cellulose acetate – an ester of cellulose and acetic acid
Rayon
Film
Vulcanized rubber – latex rubber hardened by cross-linking with sulfur
Nitrocellulose – an ester of cellulose with nitric acid
Gun cotton
Celluloid
Ping-Pong™ balls
Casein – a polymer of the protein casein made by treating cow’s milk with acid
Buttons, moldings, adhesives

106. Polymerization is the process of linking the monomer units together.
There are two processes by which polymerization may proceed—addition polymerization and condensation polymerization.
Monomer units may link head to tail, or head to head, or tail to tail during polymerization.
Head to tail most common
Regular pattern gives stronger attractions between chains than random arrangements

108. Addition Polymerization
Monomers add to the growing chain in such a manner that all the atoms in the original monomer wind up in the chain.
No other side products formed; no atoms eliminated
First monomer must “open” to start reaction.
Done with heat, or the addition of an initiator
The process is a chain reaction.
Each added unit ready to add another

109. Condensation Polymerization
Monomer units are joined by removing small molecules from the combining units.
Polyesters, polyamides lose water
No initiator is needed.
The process is a chain reaction.
Each monomer has two reactive ends, so the chain can grow in two directions.

110. Characteristics of Plastics
Transparent or translucent
Chemical resistance
Thermal and electrical insulators
Low density
Varying strengths
Kevlar
Mold or extrude
Elasticity
Regain original shape if quick stress applied
Foamed
Tend to soften when heated, rather than quickly melt