22.4 Hydrocarbon Rings

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“WE R FAMILY”
Functional groups determine the
family a substance is in.
They also
determine how
that substance is
names and it
properties
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22.4 Hydrocarbon Rings> Cyclic Hydrocarbons
A compound that contains a hydrocarbon ring
is called a cyclic hydrocarbon.
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•
Many molecules
found in nature
contain cyclic
hydrocarbons.
•
Rings with five and
six carbons are the
most abundant.
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22.4 Hydrocarbon Rings> Cyclic Hydrocarbons
• Just as straight-chain and branched-chain
alkanes can be either saturated or
unsaturated, so can cyclic hydrocarbons.
• A cyclic hydrocarbon that contains only
single bonds, and is therefore saturated is
called a cycloalkane.
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22.4 Hydrocarbon Rings> Cyclic Hydrocarbons
• To determine the
IUPAC name of a
cycloalkane, first
count the number of
carbons in the ring
and assign the
corresponding alkane
name.
Name: cyclopropane
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• Then simply add the
prefix cyclo- to the
alkane name.
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Benzene
•
•
•
has six electrons shared equally among six carbon
atoms in a ring
is written as two possible ring structures
is also represented as a hexagon with a circle
drawn inside
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Basic Chemistry
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Resonance in Benzene
• C6H6 has two resonance structures with
alternating double bonds.
• The π electrons are delocalized over the ring.
H
C
H
C
C
H
HC C C H
H
H
H
C
C
H
C
C
H
CH
C
H
Resonance structures of benzene, C6 H6
H
C
HC
H
C
C
C
H
H
CH
Abbreviated representation
of resonance structures
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Resonance in Benzene
• CC bond order is _______________
• C–C single bond = 154 pm
C=C bond = 134 pm
• CC bonds in benzene = 139 pm
π electrons delocalized
22.4 Hydrocarbon Rings> Aromatic Hydrocarbons
Substituted Aromatic Rings
• Compounds containing substituents
attached to a benzene ring are named
using benzene as the parent hydrocarbon.
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22.4 Hydrocarbon Rings> Aromatic Hydrocarbons
Substituted Aromatic Rings
When the benzene ring is a
substituent, the C6H5 group is called a
phenyl group.
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Benzene Derivatives
Aniline
C6H5NH2
Phenol
C6H5OH
TNT
trinitrotoluene
C6H4CH3(NO2)3
Aromatic Compounds in Nature
and Health
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Basic Chemistry
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Aromatic compounds are named
• with benzene as the parent chain
• with the name of a substituent in front of the
name benzene
• with common names for some substituted
compounds
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Basic Chemistry
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Naming Aromatic Compounds
When two groups are attached to benzene,
the ring is numbered to give the lower number
to the side group.
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Basic Chemistry
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Example of Naming an
Aromatic Compound
Select the correct name for the following structure:
1) chlorohexane
2)
2) chlorobenzene
chlorobenzene
3) 1-chlorobenzene
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Basic Chemistry
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Write the IUPAC name of the
following compound:
CH3
STEP 1 Write the name of the aromatic
compound.
benzene
Cl
STEP 2 Number the aromatic ring starting
from the substituent.
The ring is numbered to give the lower
number to the methyl substituent.
CH3
STEP 3 Give the location and name of each
substituent as a prefix to the name.
3-chloromethylbenzene
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1
2
3
Cl
Draw the condensed structural formula for
1-bromo-3,4-dichlorobenzene.
The name indicates a benzene
ring with one bromine atom and
two chlorine atoms. Counting
the carbon attached to the
bromine atom as carbon 1, the
chlorine atoms are attached to
carbons 3 and 4.
Br
Cl
Cl
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22.4 Hydrocarbon Rings> Aromatic Hydrocarbons
Substituted Aromatic Rings
• There are three constitutional isomers for
dimthylbenzene (C6H4(CH3)2).
• The boiling points of the three compounds
are a reminder that constitutional isomers
have different physical properties.
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22.4 Hydrocarbon Rings> Aromatic Hydrocarbons
Substituted Aromatic Rings
• In the IUPAC naming system, the possible positions of
two substituents in disubstituted benzene are
designated as 1,2; 1,3; or 1,4.
• Common names for disubstituted benzenes use the
terms ortho, meta, and para (abbreviated as o, m, and
p) in place of numbers.
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Naming Benzene Derivatives
Cl
1
6
2
3
5
4
Ortho to Cl
Meta to Cl
Para to Cl
1,4-dimethylbenzene
Common name: Para-xylene
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Simple ORGANIC Reactions
COMBUSTION
ADDITION
REACTIONS
ESTERIFICATION
SUBSTITUTION
Substitution Reactions
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Reactions of Aromatics
• Substitutions — not additions — are
typical.
CH3
+ CH3Cl
AlCl3
AlCl3 is a catalyst.
+ HCl
Addition Reactions
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Reactions of Alkenes:
ADDITION REACTIONS
• Alkenes are unsaturated — more
bonds can form to the C atoms
• Molecules such as Br2, H2, HCl, HBr, and
H2O add to the double bond
H
C C + Br2
H
H
H
Br Br
H C C H
H H
1,2-dibromoethane
An Addition Reaction
• Fats can be “hydrogenated” with H2.
Peanut butter has partially hydrogenated
vegetable oil.
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H2 C
HC
H2 C
O
O CR
O
O CR
O
O CR
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Fats and Oils
Fats with C=C bonds are usually LIQUDS
Oleic acid: a
monounsaturated
fatty acid
C=C bond
H2 C
HC
H2 C
O
O CR
O
O CR
O
O CR
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Fats and Oils
Fats with saturated acids (no C=C
bonds) are SOLIDS.
Saturated fats are
more common in
animals.
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Fats
H2 C
HC
H2 C
O
O CR
O
O CR
O
O CR
What is the
functional group
in a fat or oil?
R = organic group
with NO C=C bonds
C12 = Lauric acid
C16 = Palmitic acid
C18 = Stearic acid
R = organic group
with C=C bonds
C18 = oleic acid
Esterification
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Acids + Alcohols --> ESTERS
Esters have generally pleasant odors
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Acids + Alcohols --> ESTERS
O
O
CH 3COH + CH 3CH 2OH
Acetic acid
H+
CH 3COCH 2CH 3 + H 2O
Ethyl acetate
Ethanol
O
O
RC—O—H
+ R'—O—H
Carboxylic acid
Alcohol
H+
RC—O—R' + H 2O
Ester
One of the important reactions in nature!
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Acids + Alcohols --> ESTERS
3-methylbutanol
Acetic acid
O
H3C
C
CH3
O
CH2 CH2CHCH3
3-methylbutylacetate
Combustion
C
S
E
A
A
C
A
E
A
S

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