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Hydrocarbons
aromatic
aliphatic
Alkane
alkene
alkyne
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Unsaturated hydrocarbons
Some of them have pleasant odors.
Aromatic compounds
Aromatic hydrocarbons
1. Unsaturated ring compounds which contain
a benzene ring in their molecules, C6H6 .
2. Compounds that are far more stable than
they should be and resist the addition
reactions
typical
of unsaturated
aliphatic
compounds.
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H
H
Aromatic Compounds
H
C
C
C
C
Arene: A compound containing one or more benzene rings.
C
C
H
H
benzene
H
ek ulé structure
A Keku lé structu re
w ing all atoms as a line-angle formula
Aryl group: When we remove
Naphthalene
H
C
C
C
C
C
C
H
Phenyl C6H5H
H
Kek ulé structure
A Keku lé structu re
Phena
a H atom from an arene (Ar-)
H
H
Anthracene

Benzene C6H6

Methylbenzene C7H8

Ethylbenzene C8H10
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Many aromatic compounds are common in
nature and in medicine.
Aspirine
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Six carbon atoms joined to form a
hexagonal ring.
 Each carbon has four valence electrons
 One of these is used to form a bond with
a hydrogen atom.
 Two other electrons are used to form
sigma bonds with the carbon atoms on
the either side.

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Aromatic compounds are named with
benzene as the parent chain. One side
group is named in front of the name
benzene.
CH3
methylbenzene
Cl
chlorobenzene
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• A benzene substituent is called a phenyl group, and it can be
abbreviated in a structure as “Ph-”.
• Therefore, benzene can be represented as PhH, and phenol would be
PhOH.
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• To name a benzene ring with one substituent, name the substituent
and add the word benzene.
• Many monosubstituted benzenes have common names which you
must also learn.
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OH
n ol
Some substituted benzenes have common names
CH
OH3
Toluene
Phen
ol
OCH3
A nisole
NH2
A niline
OH
OCH
3
NHOCH
2 3
O
NH
2
C-H
Phen ol A niline
A nisoleBenAzaldehyde
niline Ben
A nisole
O
C-H
Ben zaldehyde
O
C-OH
Benzoic acid
• There are three different ways that two groups can be attached to a benzene ring,
so a ortho, meta, or para—can be used to designate the relative position of the
two substituent.
ortho-dibromobenzene
or
o-dibromobenzene
or 1,2-dibromobenzene
meta-dibromobenzene
or
m-dibromobenzene
or 1,3-dibromobenzene
para-dibromobenzene
or
p-dibromobenzene
or 1,4-dibromobenzene
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• If the two groups on the benzene ring are different,
alphabetize the names of the substituents preceding the
word benzene.
• If one substituent is part of a common root, name the
molecule as a derivative of that monosubstituted benzene.
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For three or more substituents on a benzene ring:
1. Number to give the lowest possible numbers around the ring.
2. Alphabetize the substituent names.
3. When substituents are part of common roots, name the molecule as
a derivative of that monosubstituted benzene. The substituent that
comprises the common root is located at C1.
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1
NO2
2
NO2
OH
CH3
3
4
Cl
4-Ch loro-2nitrotoluen e
Br
6
1
5
Br
2
3
4
Br
2,4,6-Trib romoph enol
4
3
2
Br
CH2 CH3
1
2-Bromo-1-ethyl-4n itroben zene
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Select the names for each structure:
Cl
1. Chlorocyclohexane
2. Chlorobenzene
3. 1-chlorobenzene
CH 3
1. Meta-methyltoluene
2. Meta-dimethylbenzene
3. 1,3-dimethylbenzene
CH 3
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Select the names for each structure:
Cl
2. Chlorobenzene
1. Meta-methyltoluene
2. Meta-dimethylbenzene
3. 1,3-dimethylbenzene
CH 3
CH 3
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Write the structural formulas for each of the
following:
A. 1,3-dichlorobenzene
B. Ortho-chlorotoluene
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Write the structural formulas for each of the
Cl
following:
A. 1,3-dichlorobenzene
Cl
B. Ortho-chlorotoluene
CH3
Cl
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Identify the organic family for each:
A. CH3CH2CH3
B.
C.
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Identify the organic family for each:
A. CH3CH2CH3alkane
B.
cycloalkane
aromatic
C.
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Stability of Benzene
• Benzene’s unusual behavior is not limited to hydrogenation. Benzene
does not undergo addition reactions typical of other highly
unsaturated compounds.
• Benzene does not react with Br2 to yield an addition product. Bromine
substitutes for a hydrogen atom, yielding a product that retains the
benzene ring.
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
Physical state: Benzene, methylbenzene
and ethylbenzene are liquids.

Insoluble in water.

Soluble in non-polar solvents such as
cyclohexane.
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