1. Chapter 11 Unsaturated Hydrocarbons
11.1
Alkenes and Alkynes

2. Saturated Hydrocarbons
have the maximum number of hydrogen atoms attached to each carbon atom
are alkanes and cycloalkanes with single C–C bonds
CH3–CH2–CH3

3. Unsaturated Hydrocarbons
have fewer hydrogen atoms attached to the carbon chain than alkanes
are alkenes with double bonds
are alkynes with triple bonds
Ball-and-stick models of ethene and ethyne show functional groups of double or triple bonds and bond angles.

4. Bond Angles in Alkenes and Alkynes
According to VSEPR theory:
the three groups bonded to carbon atoms in a double bond are at 120 angles
alkenes are flat because the atoms in a double bond all lie in the same plane
the two groups bonded to each carbon in a triple bond are at 180 angles

5. Ethene (Ethylene) Ethene, or ethylene,
is the simplest alkene, with the formula C2H4
has two carbon atoms connected by a double bond
has two H atoms bonded to each C atom
is flat, with all the C and H atoms in the same plane
is a plant hormone used to accelerate the ripening of fruits

6. Fragrant Alkenes
The odors associated with the smell of lemons, oranges, roses, and lavender are due to volatile compounds that are synthesized by the plants.

7. Ethyne (Acetylene)
The simplest alkyne is ethyne, which has the common name of acetylene.
Acetylene is a fuel used in welding.

8. Naming Alkenes and Alkynes
When the carbon chain of an alkene or alkyne has four or more C atoms, number the chain to give the lowest number to the first carbon in the double or triple bond. CH2=CHCH2CH3 1-butene CH3CH=CHCH3 2-butene CH3CH2C≡CCH3 2-pentyne

9. Guide to Naming Alkenes and Alkynes

10. Naming Alkenes Using the IUPAC system, name the following compounds:
CH CH3 CH3
A. CH3CHH2C=CH B. H2C=CHCHCHCH3
Step 1 Name the longest carbon chain that contains the double bond. Use the ending ene for alkenes.
CH CH3 CH3
A. CH3CHH2C=CH2 B. H2C=CHCHCHCH3
butene pentene

11. Naming Alkenes
Step 2 Number the longest carbon chain starting from the end nearer the double bond.
CH CH3 CH3
A. CH3CHH2C=CH2 B. H2C=CHCHCHCH3
1-butene pentene
Step 3 Give the location and name of each substituent (in alphabetical order) as a prefix to the alkene name.
CH CH3 CH3
A. CH3CHH2C=CH2 B. H2C=CHCHCHCH3
3-methyl-1-butene ,4-dimethyl-1-pentene

12. Naming Alkynes Using the IUPAC system, name the following compound:
CH3 CH3
HC CCHCHCH3
Step 1 Name the longest carbon chain that contains the triple bond. Use the ending yne for alkynes.
CH3 CH3
HC CCHCHCH3
pentyne

13. Naming Alkynes
Step 2 Number the longest carbon chain starting from the end nearer the triple bond.
CH3 CH3
HC CCHCHCH3
1-pentyne
Step 3 Give the location and name of each substituent (in alphabetical order) as a prefix to the alkyne name.
HC CCHCHCH3 3,4-dimethyl-1-pentyne

14. Learning Check
Write the IUPAC name for each of the following: A. CH2=CHCH2CH3 B. CH3CH=CHCH3 CH3 C. CH3CH=CCH3 D. CH3C CCH3

15. Solution 15
Write the IUPAC name for each of the following: A. CH2=CHCH2CH3 1-butene B. CH3CH=CHCH3 2-butene CH3 C. CH3CH=CCH3 2-methyl-2-butene D. CH3C CCH3 2-butyne

16. Learning Check
Write the IUPAC name for each of the following: A. CH3CH2CH2C CCH3 CH3 B. CH3CH2C=CHCH3

17. Solution 17
Write the IUPAC name for each of the following: A. CH3CH2CH2C CCH3 2-hexyne CH3 B. CH3CH2C=CHCH3 3-methyl-2-pentene

18. Sample Problem 11.1 Naming Alkenes and Alkynes
Write the IUPAC name for each of the following: a. b.
Solution
a. Step 1 Name the longest carbon chain that contains the double bond. There are five carbon atoms
in the longest carbon chain containing the double bond. Replace the ane in the corresponding
alkane name with ene to give pentene.
Step 2 Number the carbon chain starting from the end nearer the double bond. Place the number
of the first carbon in the double bond in front of the alkene name.
Alkenes or alkynes with two or three carbons do not need numbers. For example, the double
bond in ethene or propene must be between carbon 1 and carbon 2.
Step 3 Give the location and name of each substituent (alphabetical order) as a prefix to the
alkene name. The methyl group is located on carbon 4.

19. Sample Problem 11.1 Naming Alkenes and Alkynes
Continued
b. Step Name the longest carbon chain that contains the triple bond. There are six carbon atoms in
the longest chain containing the triple bond. Replace the ane in the corresponding alkane name
with yne to give hexyne.
Step Number the carbon chain starting from the end nearer the triple bond. Place the number
of the first carbon in the triple bond in front of the alkyne name.
Step Give the location and name of each substituent (alphabetical order) as a prefix to the
alkyne name. There are no substituents in this formula. For cycloalkenes, the double bond is
always between carbons 1 and 2. If there is a substituent, the ring is numbered from carbon 2 in
the direction to give the lower number to the substituent.
Study Check 11.1
Draw the condensed structural formula for each of the following:
a. 2pentyne b. 2chloro1hexene

20. Chapter 11 Unsaturated Hydrocarbons
11.2
Cis–Trans Isomers

21. Cis and Trans Isomers In an alkene, the double bond is rigid
holds attached groups in fixed positions
makes cis–trans isomers possible

22. Cis–Trans Isomers In cis–trans isomers,
there is no rotation around the double bond in alkenes
groups attached to the double bond are fixed relative to each other
You can make a “double bond” with your fingers with both thumbs on the same side or opposite from each other.

23. Cis–Trans Isomers Two isomers are possible when the
groups attached to each side of
the double bond are different.
In a cis isomer, the alkyl groups are attached on one side of the double bond and H atoms are on the other side.
In the trans isomer, the groups and H atoms are attached on opposite sides.
Ball-and-stick models of the cis and trans isomers of 2-butene.

24. Cis–Trans Isomerism
Alkenes cannot have cis–trans isomers if a carbon atom in the double bond is attached to identical groups.
Identical Identical
2-Bromopropene ,1-Dibromoethene
(not cis or trans) (not cis or trans) H Br H H

25. Cis–Trans Isomers in Nature
Insects emit tiny quantities of pheromones, which are chemicals that send messages.
The silkworm moth attracts other moths by emitting bombykol, which has one cis and one trans double bond.
Pheromones allow insects to attract mates from a great distance.

26. Naming Cis–Trans Isomers
The prefix of cis or trans is placed in front of the alkene name when the compound is a cis or trans isomer.
cis trans
cis-1,2-dibromoethene trans-1,2-dibromoethene

27. Learning Check
Name each, using cis or trans prefixes when needed.

28. Solution Name each, using cis or trans prefixes when needed.
cis-1,2-dibromoethene
trans-2-butene
1,1-dichloropropene

29. Sample Problem 11.2 Identifying Cis–Trans Isomers
Identify each of the following as the cis or trans isomer and give its name:
a. b.
Solution
a This is a cis isomer because the two H atoms in the double bond are on the same side. The
two-carbon alkene with a bromo group on carbon 1 and a chloro group on carbon 2 is named
cis1bromo2chloroethene.
b This is a trans isomer because the two H atoms in the double bond are on the opposite sides of the
double bond. The five-carbon alkene is named trans2pentene.
Study Check 11.2
Is the following compound cis3hexene or trans3hexene?

30. Chapter 11 Unsaturated Hydrocarbons
11.3
Addition Reactions

31. Addition Reactions In alkene and alkynes,
the double or triple bond is easily broken, providing electrons to form new bonds
double and triple bonds are very reactive
in addition reactions, reactants are added to the carbon atoms in the double or triple bond

32. Hydrogenation In hydrogenation,
hydrogen atoms add to the carbon atoms of a double bond or triple bond
a catalyst such as Pt or Ni is used to speed up the reaction

33. Hydrogenation of Oils
Adding H2 to double bonds in vegetable oils produces
compounds with higher melting points
solids at room temperature, such as margarine, soft margarine, and shortening

34. Learning Check
Write an equation for the hydrogenation of 1-butene using a platinum catalyst.

35. Solution
Write an equation for the hydrogenation of 1-butene using a platinum catalyst. Pt CH2=CHCH2CH3 + H2 CH3CH2CH2CH3

36. Trans Fats
The process of hydrogenation is used commercially to convert the double bonds in the unsaturated fats in vegetable oils to saturated fats such as margarine, which are more solid. Adjusting the amount of added hydrogen produces partially hydrogenated fats such as soft margarine, solid margarine in sticks, and shortenings, which are used in cooking.

37. Learning Check Write the product of each the following: Pt
CH3CH=CHCH3 + H2
+ H2

38. Solution Write the product of each the following: Pt
CH3CH=CHCH3 + H CH3CH2CH2CH3
+ H2

39. Sample Problem 11.3 Writing Equations for Hydrogenation
Draw the condensed structural formula for the product of each of the following hydrogenation reactions: a. b. c.
Solution
In an addition reaction, hydrogen adds to the double or triple bond to give an alkane. a. b. c.
Study Check 11.3
Draw the condensed structural formula of the product of the hydrogenation of 2methyl1butene, using a platinum catalyst.

40. Halogenation Reactions
In halogenation reactions,
halogen atoms such as chlorine or bromine add across a double bond
the reaction occurs without a catalyst
a dihaloalkane product results
In the general equation for halogenation, X2 is used for
either Cl2 or Br2.

41. Halogenation Reactions
The addition reaction of Br2 across a double bond is used to test for the presence of double bonds. A positive result turns a clear solution red.

42. Sample Problem 11.4 Halogenation
Draw the condensed structural formula of the product of the following reaction:
Solution
The addition of bromine to an alkene places a bromine atom on each of the carbon atoms of the double bond.
Study Check 11.4
What is the name of the product formed when chlorine is added to 1butene?

43. Hydration In the addition reaction called hydration,
an acid H+ catalyst is required
water (H−OH) adds to a double bond
an H atom bonds to one C in the double bond
an OH bonds to the other C
an alkene is converted to an alcohol
H OH H+
CH3CH=CHCH3 + HOH CH3CHCHCH3

44. Hydration When hydration occurs with a double bond that has an
unequal number of H atoms,
the H atom bonds to the C in the double bond with the more H
the OH bonds to the C in the double bond with the fewer H atoms

45. Learning Check
Write the product for the hydration of each of the following. H+ 1. CH3CH2CH=CHCH2CH3 + HOH CH3 2. CH3C=CHCH2CH3 + HOH 3. + HOH

46. Solution
Write the product for the hydration of each of the following. H+ 1. CH3CH2CH=CHCH2CH3 + HOH OH H CH3CH2CHCHCH2CH3

47. Solution
Write the product for the hydration of each of the following. CH3 H+ 2. CH3C=CHCH2CH3 + HOH CH3CCHCH2CH3 OH H

48. Solution
Write the product for the hydration of each of the following. H HOH

49. Sample Problem 11.5 Hydration
Draw the condensed structural formula of the product that forms in the following hydration reaction:
Solution
The H– and –OH from water (HOH) add to the carbon atoms in the double bond. The H– adds to the carbon with more hydrogens, and the –OH bonds to the carbon with fewer hydrogen atoms.
Study Check 11.5
Draw the condensed structural formula of the alcohol obtained by the hydration of 2methyl2butene.

50. Chapter 11 Unsaturated Hydrocarbons
11.4
Polymers of Alkenes

51. Polymers Polymers are large, long-chain molecules
found in nature, including cellulose in plants, starches in food, proteins, and DNA in the body
also synthetic, such as polyethylene and polystyrene, Teflon, and nylon
composed of small repeating units called monomers
made from reaction of small alkenes

52. Addition Reactions: Polymerization
In polymerization, small repeating units called monomers join to form a long-chain polymer in an addition reaction.
monomer unit repeats n

53. Common Synthetic Polymers
Synthetic polymers provide a wide variety of items that we use every day.

54. Common Synthetic Polymers: Polyethylene
Polyethylene is made using an addition reaction with the monomer unit ethylene. Common uses for polyethylene include plastic bottles, film, and insulation materials.

55. Common Synthetic Polymers: Polytetrafluoroethylene
Polytetrafluoroethylene, primarily used in nonstick coatings, is made using an addition reaction with the monomer unit of tetrafluoroethene.
tetrafluoroethene
polytetrafluoroethylene

56. Common Synthetic Polymers: Polypropylene
Polypropylene is used for ski and hiking clothing, carpets, and artificial joints.

57. Common Synthetic Polymers: Polystyrene
Polystyrene is used for plastic coffee cups, cartons, and insulation.

58. Common Synthetic Polymers: Polyvinylchloride
Polyvinylchloride, also known as PVC, is used for plastic pipes and tubing, garden hoses, and garbage bags.

59. Common Synthetic Polymers: Polydichloroethylene
Polydichloroethylene is used in plastic film and wraps.

60. Learning Check
Name the starting monomer and give its structure for each of the following polymers: A. polyethylene B. polyvinylchloride C. polystyrene

61. Solution
Name the starting monomer and give its structure for each of the following polymers: A. polyethylene ethene B. polyvinylchloride chloroethene C. polystyrene phenylethene, styrene

62. Learning Check
Name the monomer used to make polypropylene, and write a portion of a polypropylene polymer using three monomers.

63. Solution
Name the monomer used to make polypropylene, and write a portion of a polypropylene polymer using three monomers.

64. Recycling Plastics
Recycling is simplified by using codes on plastic items. 1 PETE Polyethylene terephtalate 2 HDPE High-density polyethylene 3 PV Polyvinyl chloride 4 LDPE Low-density polyethylene 5 PP Polypropylene 6 PS Polystyrene 7 OTHER Other plastic: fiberglass, polycarbonate, etc.

65. Learning Check
What types of plastic are indicated by the following codes? A. B. C. 3 PV 5 PP 6 PS

66. Solution
What types of plastic are indicated by the following codes? A. polyvinylchloride B. polypropylene C. polystyrene 3 PV 5 PP 6 PS

67. Sample Problem 11.6 Polymers
Give the name and draw the condensed structural formula of the starting monomers for the following polymers:
a. polypropylene b.
Solution
a. propene (propylene), b. 1,1-dichloroethene,
Study Check 11.6
What is the condensed structural formula of the monomer used in the manufacturing of PVC?

68. Chapter 11 Unsaturated Hydrocarbons
11.5
Aromatic Compounds

69. Aromatic Compounds Benzene is an aromatic compound
a ring of six C atoms and six H atoms
a flat ring structure drawn with three double bonds
represented by two structures because the electrons are shared among all the C atoms

70. Benzene Structure Benzene
has six electrons shared equally among the six C atoms
is also represented as a hexagon with a circle drawn inside

71. Aromatic Compounds in Nature and Health
Vanillin Aspirin
Ibuprofen Acetaminophen

72. Naming Aromatic Compounds
Aromatic compounds are named
with benzene as the parent chain
with one side group named in front of benzene
methylbenzene chlorobenzene

73. Some Common Names Some substituted benzene rings
have common names that have been in use for many years
with a single substituent use a common name or are named as a benzene derivative
toluene aniline phenol
(methylbenzene) (benzenamine) (hydroxybenzene)

74. Naming Aromatic Compounds
When two groups are attached to the benzene ring, the ring is numbered to give the lowest numbers to the side groups.
3-chlorotoluene ,3-dichlorobenzene chlorophenol

75. Learning Check
Select the correct name for each compound. 1. A. chlorocyclohexane B. chlorobenzene C. 1-chlorobenzene 2. A. 1,2-dimethylbenzene B. 1,4-dimethylbenzene C. 1,3-dimethylbenzene

76. Solution
Select the correct name for each compound. 1. B. chlorobenzene 2. C. 1,3-dimethylbenzene

77. Learning Check
Write the structural formulas for each of the following:
1. 1,3-dichlorobenzene
chlorotoluene

78. Solution Write the structural formulas for each of the following:
1. 1,3-dichlorobenzene
chlorotoluene

79. Learning Check
Identify the organic family for each: A. CH3CH2CH=CH2 B. C. CH3C CH D.

80. Solution
Identify the organic family for each: A. CH3CH2CH=CH2 alkene B. cycloalkane (alkane) C. CH3C CH alkyne D. aromatic

81. Concept Map – Unsaturated Hydrocarbons

82. Sample Problem 11.7 Naming Aromatic Compounds
Give the IUPAC name for the following:
Solution
A benzene ring with a methyl substituent is named toluene. The methyl group is attached to carbon 1 and the ring is numbered to give the lower numbers. Naming the substituents in alphabetical order, this aromatic compound is
4bromo3chlorotoluene.
Study Check 11.7
Name the following compound: