Introduction to Organic Chemistry
 The Organic Molecule
 Representative hydrocarbons
 Alkanes and nomenclature
 Haloalkanes
 Cycloalkanes
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Hydrocarbons: Representative Alkanes, Alkenes
Alkynes, and Aromatic Compounds
 Hydrocarbons contain only carbon and hydrogen atoms
 Subgroups of Hydrocarbons:
Alkanes contain only carbon-carbon single bonds
Alkenes contain one or more carbon-carbon double bonds
Alkynes contain one or more carbon-carbon triple bonds
Aromatic hydrocarbons contain benzene-like stable structures
(discussed later)
 Saturated hydrocarbons: contain only carbon-carbon
single bonds e.g. alkanes
 Unsaturated hydrocarbons: contain double or triple
carbon-carbon bonds e.g. alkene, alkynes, aromatics
Contain fewer than maximum number of hydrogens per carbon
Capable of reacting with H2 to become saturated
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Representative Hydrocarbons
 Alkanes
 Principle sources of alkanes are natural gas and
petroleum
Smaller alkanes (C1 to C4) are gases at room temperature
 Methane is
A component of the atmosphere of many planets
Major component of natural gas
Produced by primitive organisms called methanogens found in
mud, sewage and cows’ stomachs
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Methane and Global Warming
• Methane is more directly related to food production and
population growth so it could also dominate
in the near future
• Frozen methane is also found in the Arctic Ice Caps
and will be released due to global warming thus
exacerbating the problem.
• This is far more serious than people realize.
• A potentially serious effect.
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Alkenes
 Ethene (ethylene) is a major industrial feedstock
Used in the production of ethanol, ethylene oxide and the polymer
polyethylene
 Propene (propylene) is also very important in
industry
 Molecular formula C3H6
 Used to make the polymer polypropylene and is the
starting material for acetone
Can you give the structural formula for propene?
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Alkenes
 Many alkenes occur naturally
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Turpentine
• An organic solvent and synthetic material
Turpentine has been used medically since
ancient times.
• A highly effective treatment for lice.
• When mixed with animal fat is a primitive
chest rub for nasal and throat ailments.
• Drinking turpentine is extremely dangerous
and can be life threatening. In addition,
drinking turpentine is not an effective way
to induce an abortion.
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Alkynes
 Ethyne (acetylene) is used in welding torches because it
burns at high temperature
 The following reaction is a good example of making
organic material from inorganic materials.
CaC2 + 2H2O → C2H2 + Ca(OH)2
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Alkynes
 Many alkynes are of biological interest
 Capillin is an antifungal agent found naturally
 Dactylyne is a marine natural product
 Ethinyl estradiol is a synthetic estrogen used in oral
contraceptives
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What’s the structural formula for C6H6?
Total e = 24 + 6 = 30
H
C-C-C-C-C-C
H
30-10-12=8
HHHH
H
C-C-C-C-C-C
H
Molecules with
single electrons
are not stable.
HHHH
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Benzene: A Representative Hydrocarbon
 Benzene is the prototypical aromatic compound
 The Kekulé structure (named after August Kekulé
who formulated it) is a six-membered ring with
alternating double and single bonds
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Benzene: A Representative Hydrocarbon
 Benzene does not actually have discreet single and
double carbon-carbon bonds
All carbon-carbon bonds are exactly equal in length (1.38 Å)
This is between the length of a carbon-carbon single bond and a
carbon-carbon double bond
 Resonance theory explains this by suggesting there are
two resonance hybrids that contribute equally to the real
structure
The real structure is often depicted as a hexagon with a circle in
the middle
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Nomenclature: Alkanes
IUPAC - International Union of Pure and Applied Chemistry
# of Cs
1
2
3
4
5
6
7
8
9
10
MF
CH4
C 2H 6
C 3H 8
C4H10
C5H12
C6H14
C7H16
C8H18
C9H20
C10H22
Name
methane
ethane
propane
butane
pentane
hexane
heptane
octane
nonane
decane
General formula: CnH2n+2
Chapter 11 & 12
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IUPAC Rules
For acyclic saturated hydrocarbons, use the ending suffix
-ane.
Linear alkanes named according to their chain length.
e.g.
butane
heptane
For branched alkanes, find the longest continuous chain
e.g.
5-ethylnonane
Chapter 11
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IUPAC Rules
Groups attached to the chain are called substituents.
Saturated hydrocarbon substituents are called alkyl groups
(substituting –ane with –yl).
e.g.
# of Cs
1
2
3
4
5
6
7
8
9
10
MF
CH3
C 2H 5
C 3H 7
C 4H 9
C5H11
C6H13
C7H15
C8H17
C9H19
C10H21
Chapter 12
Name
methyl
ethyl
propyl
butyl
pentyl
hexyl
heptyl
octyl
nonyl
decyl
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IUPAC Rules
The main chain is numbered to give the first substituent
the lowest number. In addition, if more than 1 identical
group is attached to the chain, use prefix di, tri or tetra.
If there are 2 or more different substituents, list them
alphabetically
e.g.
Punctuation is important.
- Hydrocarbons are written as 1 word
- Use commas to separate numbers
- Use hyphens to separate numbers & names
5-ethyl-2,8-dimethyldecane
Chapter 12
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Classifying Carbons
e.g.
Carbon centers are classified as follows:
-Primary carbons are connected to only one
other carbon
-Secondary carbons are connected to two
other carbon
-Tertiary carbons are connected to three
other carbon
Chapter 12
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In-Class Practice
How about drawing the structures for
2,2,4-trimethylpentane
4,7-diethyl-5-(2-methylpropyl)decane
Chapter 12
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Haloalkanes
Substituent
F
Cl
Br
I
fluorochlorobromoiodo-
e.g. Give the structure of 5-chloro-3,3-diiodooctane
Name this compound:
Cl
Br
Chapter 12
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Haloalkanes
Simple haloalkanes are commonly called Alkyl Halides.
F
CH3-Cl
IUPAC:
CH3-CH2-Br
chloromethane
Common Methyl chloride
name:
CH3-CH-CH3
Bromoethane
2-fluoropropane
Ethyl bromide
isopropylfluoride
Chapter 12
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Haloalkanes
Halomethanes have common names that do not
indicate their structures.
Cl
Cl
CH2-Cl Cl
CH
Cl
Cl
C
Cl
Cl
Cl
IUPAC: dichloromethane
trichloromethane
Common: Methylene chloride
chloroform
Chapter 12
tetrachloromethane
Carbon tetrachloride
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Haloalkanes as Common Solvent and Anesthetics
Dry cleaners used CCl4 for grease removal.
CCl4 is toxic to liver and can cause cancer.
Residual CCl4 still in the environment from the 1920s.
Today dry cleaners use other haloalkanes such as
CH2Cl2, 1,1,1-trichloroethane, and FCl2C-CClF2.
CHCl3 was once used as an anesthetic but now we
know that it is toxic and maybe carcinogenic.
CCl3F (Freon 11) and CCl2F2 (Freon 12), CFCs, were
widely used as propellants and refrigerants in home
and car air conditioners.
CFCs catalyze the decomposition of ozone therefore
thinning the ozone layer in the stratosphere.
One chlorine atom can destroy 100,000 ozone
molecules.
Chapter 12
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Halomethanes as DBPs
DBP=disinfection by product.
Disinfecting water with Cl2 causes the formation of
CH3Cl, CH2Cl2, CHCl3, and CCl4.
These contribute to CFCs in the environment and the
ecosystem.
AIR
Absorption
volatilization
WATER
Sediment
Chapter 12
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Naming Cycloalkanes
Fit the general MF = CnH2n
Add cyclo in front of the alkane name.
e.g.
Br
Cl
Br
H
CH3
H3C
1-bromo-3-chloro-1-methylcyclohexane
CH3
3-bromo-1,1-dimethylcyclobutane
Going around the ring to
give the lowest location #
Chapter 12
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