Ch. 16: Solutions
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Transcript Ch. 16: Solutions
Ch. 11: Unsaturated
Hydrocarbons
Chem 20
El Camino College
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Unsaturated Hydrocarbons
Unsaturated means that the molecule
contains one or more multiple bonds
Alkenes contain a double bond
Alkynes contain a triple bond
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Label as alkane, alkene, or alkyne
H3C
alkene
C
C
alkyne
CH3
alkene
alkane
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Naming
Name the longest carbon chain that
contains the multiple bond (-ene or –yne)
Number the chain to give the multiple bond
the lowest number, show location
Give the location and name of each
substituent in alphabetical order, using
numbers, hyphens, and commas between
numbers
Give location of the double bond (if needed)
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Name These
H
C
H2C
CH3
H3C
C
H2
propene
C
C
CH3
2-butene
1-butene
2-butyne
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Name These
Br
H
C
CH3
HC
C
H2C
C
C
H2
CH
Br
2-methylpropene
Br
Cl
4,4-dibromo-1-butyne
3-bromo-3-chloro-1-butene
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Draw These
F
1-chloro-1,2,2-trifluoroethene
C
F
F
C
H
H
H
1,2-dimethyl-1-cyclohexene
Cl
CH3
H
C
C
H
CH3
H
H
H3C
1,1,4,4-tetrabromo-2-pentyne
Br
H
C
Br
Br
C
CH
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Br
Cis-Trans Isomers
cis--on the same side of the double bond
trans--on opposite sides of the double bond
The cis and trans isomers are different
molecules and have different properties
cis-2-butene bp = 3.7 oC
trans-2-butene bp = 0.3 oC
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Cis-Trans Isomers
The groups that are cis and trans may differ
cis & trans do not refer to gps on the same C
The words cis and trans come first in the names,
followed by a hyphen
H
Br
H
H
F
H
F
Br
trans-1-bromo-2-fluoroethene
cis-1-bromo-2-fluoroethene
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Write the names
1-pentene
4-chloro-1-pentene
Cl
trans-3-heptene
H
H
Br
cis-1-bromo-1-butene
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Write the names
H3CH2C
CH2CH3
C
cis-3,4-dibromo-3-hexene
C
Br
Br
H3CH2C
Br
C
Br
trans-3,4-dibromo-3-hexene
C
CH2CH3
Br
trans-4,4,6,6-tetrabromo-2-hexene
Br
Br
Br
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Addition Reactions
In addition reactions of alkenes, the double
bond breaks and two atoms add to the
molecule
C
C
+
A
B
A
B
C
C
We’ll study some addition reactions
Addition of H2 (hydrogenation)
Addition of X2 (halogenation)
Addition of H2O (hydration)
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Hydrogenation
In hydrogenation reactions of alkenes, the
double bond breaks & 2 H atoms add
A catalyst such as Pt, Ni, or Pd speeds up
the reactions
A cmpd with a multiple bond is unsaturated
A cmpd with single bonds only is saturated
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Hydrogenation
Double bonds react with 1 molecule of H2
Triple bonds react with 2 molecules of H2
C
C
C
C
+
+
H
2 H
H
H
Ni
Pd
H
H
C
C
H
H
C
C
H
H
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Write Product, Name
Reactant & Product
+
H
H
Pd
cyclopentene
cyclopentane
+
H
H
trans-4-methyl-2-pentene
Pt
2-methylpentane
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Halogenation
Double bond reacts with 1 molecule of bromine
Addition of bromine is useful for detection of carboncarbon double bond
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Bromination
One cyclohexene molecule reacts with 1 molecule of
bromine to give 1,2-dibromo cyclohexane
Rapid decolorization of a bromine solution is
characteristic of compound containing carbon-carbon
double bond
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Hydration
In hydration reaction of alkene, the double
bond breaks, H and OH add with formation
of an alcohol
An acid catalyst (shown as H+) is used
If the two “C”s of the double bond are
attached to different groups, H adds to the
carbon of the double bond with more “H”s.
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Hydration
H
H
C
C
H
OH
H
H
H3C
H
C
H3C
H
H+
C
H
H
OH
H+
H3C
H
OH
C
C
H
H
H
OH
H
C
C
CH3
H
H
side with more "H"s
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Write Product, Name Reactant,
OH
+
H
OH
H+
C6H12O
cyclohexene
OH
+
H
OH
H+
C5H12O
2-methyl-2-butene
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3-D (Spatial) Drawings
Bonds lying on the plane of the paper are shown
with ordinary lines
Bonds coming out of the page are shown as solid
wedges
Bonds going to the back of the page are shown as
dashed (striped, broken)wedges
H
C
H
H
H
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3-D (Spatial) Drawings
H3C
CH2
CH2
H3C
is the same as
OH
H
O
is the same as
H
H
C
C
H
H
H
O
H
Note--every tetrahedral will have two lines,
one broken wedge(dash), and one solid
wedge. The lines make the zig-zag chain.
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3-D (Spatial) Drawings
Draw a spatial drawing for butane
H
H
H
C
H
H
C
C
H
C
H
H
H
H
Draw a spatial drawing for 2,2-dibromopropane
Br
Br
H
C
H
C
H
C
H
H
H
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3-D (Spatial) Drawings
Do not show planar atoms with dashes or wedges
H
H
H
H
H
H
C
C
H
C
C
H
H
ethene
ethyne
H
C
H
H
1-propene
Draw a spatial drawing for trans-1-bromo-1H
H
propene
H
C
H
C
Br
C
H
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Aromatic Hydrocarbon
Benzene molecule, C6 H6 , consists of a ring of six
carbon atoms with one hydrogen atom attached to
each carbon.
Each carbon atom uses three valence electrons to
bond to hydrogen atom and two adjacent C atoms
Six electrons are shared equally among six
carbon atoms
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Naming of Aromatic
Hydrocarbon
When benzene has only one substituent the
benzene ring is not numbered.
Example Chlorobenzene
When there are 2 or more substituents the
benzene ring is numbered to give the lower
numbers to the substituents.
Example 1,3-dichlorobenzene
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Common name of Aromatic
Compounds
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Naming of Aromatic
Hydrocarbon
When a common name such as toluene, phenol
or aniline is used, the carbon atom attached to the
methyl, hydroxyl, or amine group is number as
carbon 1
Example: 2-chlorotoluene
Example: 4-ethyltoluene
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Polycyclic Aromatic
Compounds (PAHs)
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Polymer
Polymer are large molecules that consist of
small units called monomers
Many are made by addition reaction of
alkenes. Examples:
Polyethylene monomer is ethylene
Polyvinyl chloride monomer is vinyl chloride
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