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Chapter 13 Alkanes, Alkynes, and Aromatic Compounds

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Title: Chapter 13 Alkanes, Alkynes, and Aromatic Compounds


1
Chapter 13 Alkanes, Alkynes, and Aromatic
Compounds
2
Saturated Hydrocarbons
  • Saturated hydrocarbons
  • Have the maximum number of hydrogen atoms
    attached to each carbon atom.
  • Are alkanes and cycloalkanes with single C-C
    bonds.
  • CH3CH2CH3

3
13.1 Alkenes and Alkynes
  • Unsaturated hydrocarbons
  • Have fewer hydrogen atoms attached to the carbon
    chain than alkanes.
  • Are alkenes with double bonds or alkynes with
    triple bonds.

4
Alkenes Have Double Bonds
  • In a double bond
  • One pair of electrons form a strong sigma (?)
    bond.
  • One pair of electrons in adjacent p orbitals
    overlap to form a pi (?) bond.

5
Alkynes have Triple Bonds
  • In a triple bond
  • One pair of electrons form a strong sigma (?)
    bond.
  • Two pairs of electrons in adjacent p orbitals
    overlap to form two pi (?) bonds.

6
Bond Angles in Alkenes and Alkynes
  • According to VSEPR theory
  • The three groups bonded to carbon atoms in a
    double bond are at angles of 120.
  • The two groups bonded to each carbon in a triple
    bond are at angles of 180.

7
13.2 Naming Alkenes and Alkynes
  • In the IUPAC system, the ane ending of the
    corresponding alkane is changed to ene for
    alkenes and to yne for alkynes.

8
Naming Alkenes and Alkynes
  • When the carbon chain has 4 or more C atoms, the
    chain is numbered to give the lowest number to
    the double or triple bond.
  • 1
  • CH2CHCH2CH3 1-butene
  • 2
  • CH3CHCHCH2CH3 2-pentene
  • 3
  • CH3CH2C?CCH2CH3 3 -hexyne

9
Learning Check
  • Write the IUPAC name for each
  • A. CH3CH2C?CCH3
  • CH3
  • B. CH3CCHCH3 C.

10
Solution
  • Write the IUPAC name for each
  • A. CH3CH2C?CCH3
  • 2-pentyne
  • CH3
  • B. CH3CCHCH3 C.
  • 2-methyl-2-butene
    3-methylcyclopentene

11
13.3 The Structure of Alkenes Cis-Trans Isomerism
  • 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.

12
Cis-Trans Isomers
  • Two isomers are possible when groups are attached
    to the double bond.
  • In a cis isomer, groups are attached on the same
    side of the double bond.
  • In the trans isomer, the groups are attached on
    opposite sides.

13
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.

14
Naming Cis-Trans Isomers
  • The prefixes cis or trans are placed in front of
    the alkene name when there are cis-trans
    isomers. cis-1,2-dibromoethene
    trans-1,2-dibromoethene

15
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
    1,1-dibromoethene

16
Learning Check
  • Name each, using cis-trans prefixes when needed.

17
Solution
  • cis-1,2-dibromoethene
  • trans-2-butene
  • 1,1-dichloropropene

18
13.4 Properties of Alkenes and Alkynes
  • 13.4 Addition Reactions

19
Addition Reactions
  • The pi (?) bond is easily broken, which makes
    double and triple bonds very reactive.
  • In the addition reaction, reactants are added to
    the carbon atoms in the double or triple bond.

20
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.

21
Hydrogenation of Oils
  • When hydrogen adds to the double bonds in
    vegetable oils, the products are solids at room
    temperature.

22
Learning Check
  • Write the equation for the addition of hydrogen
    to 1-butene using a Ni catalyst.

23
Solution
  • Write the equation for the addition of hydrogen
    to 1-butene using a Ni catalyst.
  • Ni
  • CH2CHCH2CH3 H2
  • CH3CH2CH2CH3

24
Halogenation
  • In halogenation, halogen atoms add to the carbon
    atoms of a double bond or triple bond.

25
Testing for Double and Triple Bonds
  • When bromine (Br2) is added to an alkane, the red
    color of bromine persists.
  • When bromine (Br2) is added to an alkene or
    alkyne, the red color of bromine disappears
    immediately.

26
Learning Check
  • Write the product of each addition reaction

  • Pt
  • CH2CHCH3 H2

27
Solution
  • Write the product of each addition reaction
  • Pt
  • CH2CHCH3 H2 CH3CH2CH3

28
Hydrohalogenation
  • In hydrohalogenation, the atoms of a hydrogen
    halide add to the carbon atoms of a double bond
    or triple bond.

29
Markovnikovs Rule
  • When an unsymmetrical alkene undergoes
    hydrohalogenation, the H in HX adds to the carbon
    in the double bond that has the greater number of
    H.

30
Hydration Adds Water
  • In hydration, H and OH from water add to the
    carbon atoms of a double bond or triple bond to
    form alcohols (OH).
  • The reaction is catalyzed by acid H.

31
Learning Check
  • Write the products of each reaction.

32
Solution
  • Write the products of each reaction.

33
13.8 Alkene Polymers
34
Polymers
  • Polymers are
  • 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.

35
Common Synthetic Polymers

36
Polymerization
  • In polymerization, small repeating units called
    monomers are bonded to form a long chain polymer.

Repeating monomer
37
(No Transcript)
38
Recycling Plastics
  • Recycling is simplified by using codes on plastic
    items.
  • 1 PETE Polyethyleneterephtalate
  • 2 HDPE High-density polyethylene
  • 3 PV Polyvinyl chloride
  • 4 LDPE Low-density polyethylene
  • 5 PP Polypropylene
  • 6 PS Polystyrene

39
Learning Check
  • What is the starting monomer for polyvinyl
    chloride (PVC)?

40
Solution
  • What is the starting monomer for polyvinyl
    chloride (PVC)?

41
Chapter 13 Unsaturated Hydrocarbons
  • 13.6 Aromatic Compounds

42
13.9 Aromatic Compounds and the Structure of
Benzene
  • Benzene is
  • An aromatic compound.
  • A ring of 6 C atoms and 6 H atoms.
  • A flat ring structure drawn with double bonds.
  • Represented by two structures because the
    electrons move among the C atoms.

43
Benzene Structure
  • Because the pi electrons in benzene are shared
    equally among the 6 C atoms, benzene can also be
    represented as a hexagon with a circle drawn
    inside.

44
Aromatic Compounds in Nature and Medicine
45
13.10 Naming Aromatic Compounds
  • A benzene with a single substituent is often
    named as a benzene derivative.
  • Methylbenzene Chlorobenzene

46
Some Common Names
  • Some substituted benzene rings have common names
    that have been in use for many years.

47
Naming Aromatic Compounds
  • A benzene ring with two or more substituents is
    numbered to give the lowest numbers to the side
    groups.
  • Common names use the prefixes ortho- (1,2-),
    meta- (1,3-) and para- (1,4-).

48
Learning Check
  • Select the correct name for each structure
  • 1) chlorocyclohexane
  • 2) chlorobenzene
  • 3) 1-chlorobenzene
  • 1) 1,3-dichlorobenzene
  • 2) o-dichlorobenzene
  • 3) m-dichlorobenzene

49
Solution
  • Select the correct name for each structure
  • 2) Chlorobenzene
  • 1) 1,3-dichlorobenzene
  • 3) m-dichlorobenzene

50
Learning Check
  • Write the structural formula for each
  • A. 1-bromo-4-chlorobenzene
  • B. o-chlorotoluene

51
Solution
  • Write the structural formula for each
  • A. 1-bromo-4-chlorobenzene
  • B. o-chlorotoluene

52
Chapter 13 Unsaturated Hydrocarbons
  • 13.7 Properties of Aromatic Compounds

53
13.11 Reactions of Aromatic Compounds
  • Aromatic compounds
  • Have a stable aromatic bonding system.
  • Are resistant to many reactions.
  • Undergo substitution reactions, which retains the
    stability of the aromatic bonding system.

54
Substitution Reactions
  • In a substitution reaction, a hydrogen atom on a
    benzene ring is replaced by an atom or group of
    atoms.
  • Type of substitution H on benzene replaced by
  • Halogenation chlorine or bromine atom
  • Nitration nitro group (NO2)
  • Sulfonation SO3H group

55
Halogenation
  • Halogenation replaces a H on benzene by a
    chlorine or bromine atom.
  • A catalyst such as FeCl3 is used in chlorination
    FeBr3 in bromination.

56
Nitration
  • Nitration replaces a H on benzene by a nitro
    (NO2) group from HNO3.
  • An acid catalyst such as H2SO4 is used in
    nitration.

57
Sulfonation
  • Sulfonation replaces a H on benzene by a
  • SO3H group from SO3.
  • An acid catalyst such as H2SO4 is used in
    sulfonation.

58
Learning Check
  • Write the equation for the bromination of
    benzene, including catalyst.

59
Solution
  • Write the equation for the bromination of
    benzene, including catalyst.

60
Chapter Summary
  • Alkenes contain carbon-carbon double bonds.
  • Alkynes contain carbon-carbon triple bonds.
  • Aromatic compounds contain six carbons in a ring
    arrangement with three double and three single
    bonds alternating between carbon atoms.
  • Alkenes are named using the family ending ene,
    while the alkynes use the family ending yne.
  • Alkenes and alkynes generally undergo addition
    reactions and aromatic compounds generally
    undergo substitution reactions.
  • Reaction mechanism A description of the
    individual steps by which old bonds are broken
    and new bonds are formed.

61
  • End of Chapter 13

62
Thank you
  • Thanks so much for a wonderful semester. You have
    been so wonderfully Kind to me.
  • I love you so much and will miss you.
  • Love
  • Divan
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