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. Chapter 11 Unsaturated Hydrocarbons
11.2
Cis–Trans Isomers

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

20. 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.

21. 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.

22. 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

23. 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.

24. 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

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

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

27. Chapter 11 Unsaturated Hydrocarbons
11.3
Addition Reactions

28. 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

29. 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

30. 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

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

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

33. 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.

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

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

36. 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.

37. 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.

38. 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

39. 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

40. 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

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

42. 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

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

44. Chapter 11 Unsaturated Hydrocarbons
11.4
Polymers of Alkenes

45. 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

46. 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

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

48. 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.

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

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

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

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

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

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

55. 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

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

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

58. 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.

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

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

61. Chapter 11 Unsaturated Hydrocarbons
11.5
Aromatic Compounds

62. 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

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

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

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

66. 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)

67. 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 ,4-dichlorobenzene chlorophenol

68. 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

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

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

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

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

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

74. Concept Map – Unsaturated Hydrocarbons