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Chapter 22Hydrocarbon Compounds
22.1 Hydrocarbons
22.2 Unsaturated Hydrocarbons
22.3 Isomers22.4 Hydrocarbon Rings22.5 Hydrocarbons from Earth’s Crust
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What does it mean if a fat is unsaturated?
For example, olives are high in unsaturated fat but low in saturated fat.
CHEMISTRY & YOUCHEMISTRY & YOU
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Alkenes
What are the structural characteristics of alkenes?
AlkenesAlkenes
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• An organic compound that contains the maximum number of hydrogen atoms per carbon atom is called a saturated compound.
• Alkanes are saturated compounds because the only bonds in alkanes are single covalent bonds.
AlkenesAlkenes
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• An organic compound that contains double or triple carbon-carbon bonds is called an unsaturated compound.
• The ratio of the hydrogen atoms to carbon atoms is lower in an unsaturated compound than in a saturated compound.
• An alkene is a hydrocarbon that contains one or more carbon-carbon double covalent bonds.
AlkenesAlkenes
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At least one carbon-carbon bond in an alkene is a double covalent bond. Other bonds may be single carbon-carbon bonds and carbon-hydrogen bonds.
AlkenesAlkenes
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• Ethene (C2H4) is the simplest alkene.
• It is often called by the common name ethylene.
AlkenesAlkenes
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• To name an alkene by the IUPAC system, find the longest chain that contains the double bond.
• This chain is the parent alkene.
• It has the root name of the alkane with the same number of carbons plus the ending -ene.
AlkenesAlkenes
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• The chain is numbered so that the carbon atoms of the double bond have the lowest possible numbers.
• Substituents on the chain are named and numbered in the same way they are for alkanes.
AlkenesAlkenes
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What is the difference between propene and propane?
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What is the difference between propene and propane?
Propene is an alkene with three carbons and one carbon-carbon double bond. Propane is an alkane with three carbons and no carbon-carbon double bonds.
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Describe how saturated and unsaturated fats differ structurally.
CHEMISTRY & YOUCHEMISTRY & YOU
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13
Describe how saturated and unsaturated fats differ structurally.
An unsaturated fat is a fat that contains double or triple carbon-carbon bonds.
CHEMISTRY & YOUCHEMISTRY & YOU
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Alkynes
What are the structural characteristics of alkynes?
AlkynesAlkynes
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• A hydrocarbon that contains one or more carbon-carbon triple covalent bonds is called an alkyne.
• A carbon-carbon triple bond is shown in structural formulas as three parallel lines.
AlkynesAlkynes
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At least one carbon-carbon bond in an alkyne is a triple covalent bond. Other bonds may be single or double carbon-carbon bonds and carbon-hydrogen bonds.
• Like alkenes, alkynes are unsaturated compounds.
AlkynesAlkynes
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• Alkynes are not plentiful in nature.
• The simplest alkyne is the gas ethyne (C2H2), which has the common name acetylene, and is shown at left.
• The triple bond restricts rotation in an ethyne molecule, which has a linear shape.
AlkynesAlkynes
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• As a result, the introduction of a double or triple bond into a hydrocarbon does not have a dramatic effect on physical properties such as boiling point.
Like alkanes, the major attractions between alkenes and alkynes are weak van der Waals forces.
Bo
ilin
g p
oin
t (º
C) 0
–20
–40
–60
–80
–100
–120
AlkynesAlkynes
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19
What is the difference between ethene and ethyne?
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What is the difference between ethene and ethyne?
Ethene is an alkene containing two carbons in a carbon-carbon double bond. Ethyne is an alkyne containing two carbons in a carbon-carbon triple bond.
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At least one carbon-carbon bond in an alkene is a double covalent bond. Other bonds may be single carbon-carbon bonds and carbon-hydrogen bonds.
At least one carbon-carbon bond in an alkyne is a triple bond. Other bonds may be single or double carbon-carbon bonds and carbon-hydrogen bonds.
Key ConceptsKey Concepts
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• saturated compound: an organic compound in which all carbon atoms are joined by single covalent bonds; it contains the maximum number of hydrogen atoms per carbon atom
• unsaturated compound: an organic compound with one or more double or triple carbon-carbon bonds
• alkene: a hydrocarbon containing one or more carbon-carbon double bonds; alkenes are unsaturated hydrocarbons
• alkyne: a hydrocarbon containing a carbon-carbon triple bond; alkynes are unsaturated hydrocarbons
Glossary TermsGlossary Terms