Transcript Introductory Chemistry: Concepts & Connections 4th Edition

Introductory Chemistry:
Concepts & Connections
4th Edition by Charles H. Corwin
Chapter 19
Organic
Chemistry
Christopher G. Hamaker, Illinois State University, Normal IL
© 2005, Prentice Hall
Introduction
• Organic chemistry is the study of carbon and its
compounds.
• The major sources of carbon are the fossil fuels:
petroleum, natural gas, and coal.
• Currently, about 7 million organic compounds
account for about 90% of all known substances.
• Each year, over 50,000 new organic compounds
are synthesized.
Chapter 19
2
Conclusions Continued
• A hydrocarbon is a compound that contains only
carbon and hydrogen.
• A hydrocarbon derivative is a compound derived
from a hydrocarbon but containing other elements
such a fluorine, nitrogen, and oxygen.
• There are two types of hydrocarbons:
– Saturated hydrocarbons
– Unsaturated hydrocarbons
Chapter 19
3
Saturated Hydrocarbons
• A saturated hydrocarbon has only single bonds
between the carbon atoms.
• Carbon can form four single covalent bonds to
other atoms.
• A saturated hydrocarbon with only single bonds
belongs to the alkane family.
Chapter 19
4
Unsaturated Hydrocarbons
• An unsaturated hydrocarbon has either a double
or triple bond between two carbon atoms.
– If it has a double bond, it is an alkene (b).
– If it has a triple bond, it is an alkyne (c).
• An aromatic hydrocarbon has a benzene ring. A
benzene ring is a 6-membered ring of carbon
atoms with alternating single and double bonds (d).
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5
Classification of Hydrocarbons
• Below is a flowchart for the classification of
hydrocarbons.
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Alkanes
• Alkanes are a family of compounds whose names
end in the suffix -ane. They are saturated
hydrocarbons.
• They each have the same general molecular
formula: CnH2n+2.
– The fifth member of the alkane family, pentane, has 5
carbon atoms and (2 × 5 + 2 = 12) hydrogen atoms,
C5H12.
Chapter 19
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Alkane Family
• The lighter alkanes (1 – 10 carbons) are used as
fuels while the larger alkanes (20 – 40 carbons)
are solids used to make waxes and candles.
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8
Structural Isomers
• Two compounds with the same molecular formula
but different structural formulas are isomers.
• Butane has the formula C4H10. We can draw the
formula in two ways:
CH3CH2CH2CH3 and CH3CH(CH3)CH3
• The two isomers have different physical
properties.
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9
Alkyl and Aryl Groups
• When a hydrogen is removed from an alkane, an
alkyl group results.
CH4 - H = CH3–
methane
methyl group
CH3-CH3 - H = CH3-CH2–
ethane
ethyl group
• When we remove the hydrogen atom, the name
-ane suffix is changed to -yl.
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Alkyl and Aryl Groups
Chapter 19
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Guidelines for Naming Alkanes
1. Name an alkane for its longest continuous carbon
chain regardless of the branches.
2. Number the longest continuous chain starting
from the end closest to the first branch on the
chain.
3. Indicate the position of the alkyl groups by name
and number.
4. If there are two or more of the same group
attached to the chain, use the prefixes di-, tri-,
tetra-, etc.
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Nomenclature of Alkanes
• What is the name of the following alkane?
CH3
CH3 CH3 CH2 CH2 CH CH3
6
5
4
3
2
1
• The longest chain has 6 carbons, so it is a hexane
derivative. The methyl group is in the 2 position.
• The name is 2-methylhexane.
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Nomenclature of Alkanes
• What is the name of the following alkane?
5
4
3
2
1
• The longest chain has 5 carbons, so it is a pentane
derivative. The methyl groups are in the 2 and 3
positions.
• The name is 2,3-dimethylpentane.
Chapter 19
14
Alkane Reactions
• The C-C and C-H bonds in alkanes are very
strong and unreactive at room temperature.
• At high temperatures, alkanes burn rapidly in the
presence of oxygen. This is a combustion
reaction.
spark
CH4(g) + 2 O2(g) → CO2(g) + 2 H2O(g)
• The products of a combustion reaction are carbon
dioxide and water.
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Alkene & Alkyne Formulas
• Alkenes contain one or more double bonds. The
general molecular formula for an alkene with one
double bond is CnH2n.
– The fifth member of the alkene family, pentene, has 5
carbon atoms and (2 × 5 = 10) hydrogen atoms, C5H10.
• Alkynes contain one or more triple bonds. The
general molecular formula for an alkyne with one
triple bond is CnH2n-2.
– The fifth member of the alkyne family, pentyne, has 5
carbon atoms and (2 × 5 – 2 = 8) hydrogen atoms,
C5H8.
Chapter 19
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Alkene Family
• Butene, C4H8, has two structural isomers. The
double bond can be between the first and second
carbon or between the second and third carbon.
Chapter 19
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Guidelines for Naming Alkenes
1. Name an alkene for its longest continuous carbon
chain that contains the double bond. The name
is the same as the alkane with the -ane suffix
changed to -ene.
2. Number the longest continuous chain starting
from the end closest to the double bond.
3. Indicate the position of the attached alkyl groups
by name and number.
4. If there are two or more of the same group
attached to the chain, use the prefixes di-, tri-,
tetra-, etc.
Chapter 19
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Nomenclature of Alkenes
• What is the name of the following alkene?
5
4
3
2
1
• The longest chain with the double bond has 5
carbons, so it is a pentene derivative. The double
bond is the first bond, so it is a 1-pentene. The
ethyl group is in the 2 position.
• The name is 2-ethyl-1-pentene.
Chapter 19
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Alkyne Family
• Butyne, C4H6, has two structural isomers. The
triple bond can be between the first and second
carbon or between the second and third carbon.
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Guidelines for Naming Alkynes
1. Name an alkene for its longest continuous carbon
chain that contains the triple bond. The name is
the same as the alkane with the -ane suffix
changed to -yne.
2. Number the longest continuous chain starting
from the end closest to the triple bond.
3. Indicate the position of the attached alkyl groups
by name and number.
4. If there are two or more of the same group
attached to the chain, use the prefixes di-, tri-,
tetra-, etc.
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Nomenclature of Alkynes
• What is the name of the following alkyne?
1
2
3
4
• The longest chain with the triple bond has 4
carbons, so it is a butyne derivative. The triple
bond is the first bond, so it is a 1-butyne. The
methyl group is in the 3 position.
• The name is 3-methyl-1-butyne.
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Reactions of Alkenes & Alkynes
• In addition to combustion reactions, alkenes and
alkynes also undergo addition reactions. The
double or triple bond can add atoms. There are
two types: hydrogenation and halogenation.
• Hydrogenation
Ni
– CH≡CH(g) + H2(g) → CH2=CH2(g)
• Halogenation
– CH2=CH2(l) + Br2(l) → CH2Br-CH2Br(l)
Chapter 19
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Polymerization Reactions
• A polymer is a giant molecule made up from
many small molecules (monomers) joined in a
long chain.
• Ethylene, CH2=CH2, can react to give
polyethlyene.
• We represent the polymer as [-CH2-CH2-]n.
n CH2=CH2 → [-CH2-CH2-]n
monomer
polymer
Chapter 19
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Arenes
• Arenes contain a benzene ring.
• Arenes are also called aromatic compounds
because of their fragrant smell.
• The formula for benzene is C6H6 and it has a
cyclic structure.
• The double bonds are
delocalized and benzene
is often written with a
circle in the middle.
Chapter 19
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Isomers of Disubstituted Benzene
• If we replace two of the hydrogens on benzene
with chlorines, we have dichlorobenzene, C6H4Cl2.
• The chlorine atoms can be arranged in three
different ways:
Chapter 19
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Isomers of Disubstituted Benzene
• If the chlorines are on
adjacent carbons, we have
ortho-dichlorobenzene.
• If the chlorines are separated
by one carbon, we have
meta-dichlorobenzene.
• If the chlorines are opposite
each other, we have
paradichlorobenzene.
Chapter 19
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Hydrocarbon Derivatives
• There are millions of organic compounds.
• We can categorize them into classes of
compounds.
• Each of the classes has a specific functional
group. A function group is a set of atoms that
gives a class of compounds its characteristics.
• There are 10 classes: five without a carbonyl
group and five with a carbonyl group (C=O).
Chapter 19
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Non-Carbonyl Classes
of Hydrocarbon Derivatives
• Here are the basic hydrocarbon classes. R is an
alkyl group and Ar is an aryl group.
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Carbonyl Classes
of Hydrocarbon Derivatives
Chapter 19
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Organic Halides
• If a halogen atom (F, Cl, Br, I) replaces a
hydrogen atom in a hydrocarbon, the new
compound is an organic halide.
• Organic halides are used primarily as household
and industrial solvents.
• They are found in many pesticides.
• They are essentially nonpolar molecules with low
boiling points and properties similar to those of
alkanes.
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Alcohols & Phenols
• When an –OH group replaces a hydrogen atom on
an alkane, the result is an alcohol.
• When an –OH replaces a hydrogen atom on a
arene, the resulting molecule is a phenol.
• The –OH group is called a hydroxyl group.
• The name of alcohols is derived from the parent
alkane by changing the -ane ending to a -ol suffix.
– For example, CH3CH2OH is ethanol
Chapter 19
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Alcohols & Phenol Continued
• Most alcohols are quite water soluble because of
the polar –OH group which allows for hydrogen
bonding.
• Alcohols higher boiling points are different than
their parent alkanes.
Chapter 19
33
Ethers
• Organic molecules with two hydrocarbon groups
attached to an oxygen are ethers, R-O-R.
• Ethers are usually named by indicating the two
groups attached to the oxygen.
• Ethers do not hydrogen bond and their properties
lie between those of alkanes and alcohols.
Chapter 19
34
Amines
• If an alkyl or aryl group replaces a hydrogen in
ammonia, an amine results, R-NH2.
• Amines are often referred to by their common
names, indicating the alkyl group present.
• Most amines are polar due to their ability to
hydrogen bond.
Chapter 19
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Aldehydes
• Aldehydes contain a carbonyl (C=O) group and are
polar.
• In an aldehyde, the carbonyl group is attached to a
hydrogen and an alkyl or aryl group, RCHO.
• The name of an aldehyde is derived from its parent
alkane by changing the -ane to an -al suffix.
Chapter 19
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Ketones
• Ketones also contain the carbonyl group and are
generally polar.
• Ketones have two alkyl or aryl groups attached to
the carbonyl group.
• Ketones are named for their parent alkane.
Chapter 19
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Carboxylic Acids
• In a carboxylic acid, a hydroxyl group and alkyl
or aryl group is bonded to a carbonyl group,
RCOOH.
• This group, -COOH, is a carboxyl group.
• Acetic acid, CH3COOH, is a major component of
vinegar and gives it its sour taste.
• Carboxylic acids are named from their parent
alkane by dropping the -ane ending and replacing
it with a -oic acid suffix.
Chapter 19
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Carboxylic Acids Continued
• Carboxylic acids are polar since the carboxyl
group, –COOH, can form hydrogen bonds.
• They have similar properties to alcohols with high
boiling points and good water solubility.
Chapter 19
39
Esters
• An ester has an –R and an –OR group bonded to a
carbonyl group, RCOOR.
• Esters typically have a pleasant, fruity odor.
• They are slightly polar.
• They are typically formed from the reaction of an
alcohol with a carboxylic acid.
Chapter 19
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Amides
• In amides, a carbonyl group is attached to an alkyl
or aryl group and an –NH2 group.
• Amides are formed from the reaction of a
carboxylic acid with ammonia.
• They are polar molecules with properties similar
to those of carboxylic acids.
Chapter 19
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Conclusions
• Organic chemistry is the study of compounds that
contain carbon.
• Hydrocarbons contain only hydrogen and carbon.
• Saturated hydrocarbons have only single carboncarbon bonds.
• Unsaturated hydrocarbons have double or triple
carbon-carbon bonds.
• Aromatic hydrocarbons have a benzene ring.
Chapter 19
42
Conclusions Continued
• Alkenes have at least one carbon-carbon double
bond.
• Alkynes have at least one carbon-carbon triple
bonds.
• Arenes contain a benzene ring.
• Hydrocarbon derivatives have a functional group
in addition to the hydrocarbon function. They are
summarized on the next slide.
Chapter 19
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Chapter 19
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