Chemistry: Matter and Change

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Chapter Menu
Hydrocarbons
Section 22.5 Introduction to Hydrocarbons Section
22.1 Alkanes Section 22.3 Alkenes and
Alkynes Section 22.4 Hydrocarbon Isomers Section
22.5 Aromatic Hydrocarbons
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Section 21-1
Section 21.1 Introduction to Hydrocarbons

• Explain the terms organic compound and organic
  chemistry.

• Identify hydrocarbons and the models used to
  represent them.
• Distinguish between saturated and unsaturated
  hydrocarbons.
• Describe where hydrocarbons are obtained and how
  they are separated.

microorganism a tiny organism, such as a
bacterium or a protozoan, that cannot be seen
without a microscope
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Section 21-1
Section 21.1 Introduction to Hydrocarbons (cont.)
organic compound hydrocarbon saturated hydrocarbon
unsaturated hydrocarbon fractional
distillation cracking
Hydrocarbons are carbon-containing organic
compounds that provide a source of energy and raw
materials.
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Section 21-1
Organic Compounds

• Chemists in the early 19th century knew living
  things produced a variety of carbon compounds,
  called organic compounds.

• They were not able to synthesize them in the lab
  and labeled them as mysterious.
• Wöhler was the first to produce an organic
  compound in the lab.

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Section 21-1
Organic Compounds (cont.)

• Organic compound is applied to all
  carbon-containing compounds
• the primary exceptions of carbon oxides,
  carbides, and carbonates, which are considered
  inorganic.

• carbon shares its electrons and forms four
  covalent bonds.

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Section 21-1
Organic Compounds (cont.)

• Carbon atoms are bonded to hydrogen atoms or
  other elements near carbon on the periodic table.

• Carbon atoms also bond to other carbon atoms and
  form long chains.

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Section 21-1
Hydrocarbons

• The simplest organic compounds are hydrocarbons,
  which consist of only the elements carbon and
  hydrogen.

• There are thousands of hydrocarbons.

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Section 21-1
Hydrocarbons (cont.)

• Carbon atoms bond to each other by single,
  double, and triple bonds.

• Saturated hydrocarbons contain only single bonds.
• Unsaturated hydrocarbons contain at least one
  double or triple bond.

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Section 21-1
Refining Hydrocarbons

• Most hydrocarbons are obtained from crude oil.

• Fractional distillation involves boiling
  petroleum and collecting each group of components
  as they condense at different temperatures.

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Section 21-1
Refining Hydrocarbons (cont.)
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Section 21-1
Refining Hydrocarbons (cont.)

• Heavier fractions are converted to gasoline or
  other lighter fractions by a process called
  cracking.

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Section 21-1
Refining Hydrocarbons (cont.)

• Natural gas 1-4 carbons
• Gasoline is not a pure substance.

• Most molecules have 5 to 12 carbons.
• octane rating system.

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Section 21-1
Section 21.1 Assessment
Petroleum is separated into usable parts by
boiling and condensing each component in a
process called ____. A. cracking B. fractional
distillation C. saturation D. bonding

1. A
2. B
3. C
4. D

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Section 21-1
Section 21.1 Assessment
What is a hydrocarbon that contains only single
bonds called? A. unsaturated B. organic
C. saturated D. fully bonded

1. A
2. B
3. C
4. D

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• quiz

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Study Guide 1
Section 21.1 Introduction to Hydrocarbons
Key Concepts

• Organic compounds contain the element carbon,
  which is able to form straight chains and
  branched chains.

• Hydrocarbons are organic substances composed of
  carbon and hydrogen.
• The major sources of hydrocarbons are petroleum
  and natural gas.
• Petroleum can be separated into components by the
  process of fractional distillation.

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End of Section 21-1
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Section 21-2
Section 21.2 Alkanes

• Name alkanes by examining their structures.

• Draw the structure of an alkane when given its
  name.
• Describe the properties of alkanes.

IUPAC (International Union of Pure and Applied
Chemistry) an international group that aids
communication between chemists by setting rules
and standards in areas such as chemical
nomenclature, terminology, and standardized
methods
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Section 21-2
Section 21.2 Alkanes (cont.)
alkane homologous series parent chain substituent
group cyclic hydrocarbon cycloalkane
Alkanes are hydrocarbons that contain only single
bonds.
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Section 21-2
Straight-Chain Alkanes

• Alkanes are hydrocarbons that have only single
  bonds between atoms.

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Section 21-2
Straight-Chain Alkanes (cont.)

• The names of alkanes end in ane.

• Prefixes are derived from Greek . Memorize these
  from page 700.
• A series of compounds that differ from one
  another by a repeating unit is called a
  homologous series.

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Section 21-2
Straight-Chain Alkanes (cont.)
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Section 21-2
Branched-Chain Alkanes

• Carbon atoms can bond to one, two, three, or four
  other carbon atoms making a variety of chains
  possible.

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Section 21-2
Branched-Chain Alkanes (cont.)

• Straight chains and branched chains can have the
  same molecular formula.

• Order and arrangement of atoms in organic
  compounds determine their identities.
• C5H12

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• When naming branched chain alkanes, the longest
  continuous chain of carbon atoms is called the
  parent chain.
• All the side branches are known as substituent
  groups.

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• C7H16

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Section 21-2
Branched-Chain Alkanes (cont.)
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Section 21-2
Branched-Chain Alkanes (cont.)

• Naming branched-chain alkanes

• Count the number of carbon atoms in the longest
  continuous chain.
• Number each carbon in the parent chain.
• Name each alkyl group substituent.
• If the same alkyl group appears more than once as
  a branch on the parent structure, use a prefix to
  indicate how many times it appears.
• When different alkyl groups are attached to the
  same parent chain, place their names in
  alphabetical order.

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Section 21-2
Branched-Chain Alkanes (cont.)

• Naming branched-chain alkanes

• Write the entire name, using hyphens to separate
  numbers from words and commas to separate numbers.

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• Isomers of pentane

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• Draw all the isomers of hexane
• Make up each with the kit provided.

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• Do question 1 to 4 page 705
• Answer to 1 2 on page 950
• 3) 2-methylpentane 2,2-dimethylpropane

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Section 21-2
Cycloalkanes

• An organic compound that contains a hydrocarbon
  ring is called a cyclic hydrocarbon.

• Cyclic hydrocarbons with only single bonds are
  called cycloalkanes.

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Section 21-2
Cycloalkanes (cont.)

• Naming substituted cycloalkanes is the same as
  straight-chains but with a few exceptions.

• The ring is always considered the parent chain.
• Numbering starts on the carbon that is bonded to
  the substituent.
• When more than one carbon has a substituent,
  number in the direction that gives the lowest
  possible numbers for the substituents.

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• Do questions 10, 11 page 708
• Answers on page 950

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Section 21-2
Properties of Alkanes

• Structure affects molecular properties.

• Alkanes are not polar and are good solvents for
  other nonpolar molecules.

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Section 21-2
Properties of Alkanes (cont.)

• Physical properties of alkanes

• Compared to water, methane boils and melts at
  lower temperatures.
• Methane molecules have little intermolecular
  attraction compared to water.

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Section 21-2
Properties of Alkanes (cont.)

• Chemical properties of alkanes

• Alkanes have low reactivity because they are
  nonpolar and have no charge, and because they
  have strong single bonds between carbon atoms.

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• Do questions 12 and 13 page 710
• A) 1-ethyl-2,4,5-trimethylcyclohexane
• B) 1,2-dipropylcyclopentane

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• NAMING AND DRAWING ALKANES
• butane 2) hexane 3) decane 4) 3 methylhexane
• 5) 2-methylhexane 6) 3-methylheptane
• 7) 3,5-dimethylheptane 8) 4-ethyl-4-propylheptane
• 9) 3,5-diethyloctane 10) 3,4,5,7-tetraethylnonane
  
• 11) 3,6-diethyl-4-methyl-7-propyldecane
• 12)cyclopentane 13) 1,2-dimethylcyclobutane
• 14) 1-ethyl-3-methylcyclohexane

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Section 21-2
Section 21.2 Assessment
What is a cyclic alkane with no substituents
groups and 6 carbon atoms? A. heptane
B. cycloheptane C. cyclohexane D. cyclobutane

1. A
2. B
3. C
4. D

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Section 21-2
Section 21.2 Assessment
Alkanes contain how many double bonds?
A. greater than 2 B. 2 C. 1 D. 0

1. A
2. B
3. C
4. D

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• Self Check Quizzes

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Study Guide 2
Section 21.2 Alkanes
Key Concepts

• Alkanes contain only single bonds between carbon
  atoms.

• Alkanes and other organic compounds are best
  represented by structural formulas and can be
  named using systematic rules determined by the
  International Union of Pure and Applied Chemistry
  (IUPAC).
• Alkanes that contain hydrocarbon rings are called
  cyclic alkanes.

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End of Section 21-2
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Section 21-3
Section 21.3 Alkenes and Alkynes

• Compare the properties of alkenes and alkynes
  with those of alkanes.

• Describe the molecular structures of alkenes and
  alkynes.
• Name an alkene or alkyne by examining its
  structure.
• Draw the structure of an alkene or alkyne by
  analyzing its name.

hormone chemical produced in one part of an
organism and transported to another part, where
it causes a physiological change
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Section 21-3
Section 21.3 Alkenes and Alkynes (cont.)
alkene alkyne
Alkenes are hydrocarbons that contain at least
one double bond, and alkynes are hydrocarbons
that contain at least one triple bond.
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Section 21-3
Alkenes

• Unsaturated hydrocarbons that contain at least
  one or more double covalent bonds between carbon
  atoms are called alkenes.

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Section 21-3
Alkenes (cont.)

• Alkenes are named in much the same way as alkanes.

• Alkenes end in ene.
• When four or more carbon atoms are present,
  specify the location of the double bond.

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Section 21-3
Alkenes (cont.)

• When naming branched-chain alkenes, follow the
  same rules as for alkanes, with two exceptions.

• The parent chain is always the longest chain that
  contains double bond, whether it is the longest
  chain or not.
• The position of the double bond, not the
  branches, determine the numbering.
• Use a prefix to designate the number of double
  bonds.

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• Examples of alkenes

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• Do problem18 and 19 page 714
• Answers on page 950

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Section 21-3
Alkenes (cont.)

• Alkenes are nonpolar and have low solubility in
  water.

• Alkenes are more reactive than alkanes because
  the double bond increases electron density
  between the two carbon atoms, providing a good
  site for chemical reactivity.

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Section 21-3
Alkynes

• Unsaturated hydrocarbons that contain one or more
  triple bonds between carbon atoms are called
  alkynes.

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Section 21-3
Alkynes (cont.)

• Straight-chain and branched-chain alkynes are
  named in the same way as alkenes, except the
  ending is yne.

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Section 21-3
Alkynes (cont.)

• Alkynes have physical and chemical properties
  similar to alkenes but are generally more
  reactive because the triple bonds cause even
  larger electron densities than double bonds.

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• Examples of alkynes

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• Do problems 21 page 716
• 1-butyne
• 5-methyl-3-heptene
• 4-methyl-1,3-pentadiene
• 2,3-dimethyl-2-butene

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Section 21-3
Section 21.3 Assessment
Which of the following is generally the most
reactive? A. cycloalkanes B. alkanes
C. alkenes D. alkynes

1. A
2. B
3. C
4. D

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Section 21-3
Section 21.3 Assessment
What is the name of a straight-chain hydrocarbon
with six carbon atoms and a triple bond between
the second and third carbon atoms? A. 2-hexene
B. 3-hexene C. 2-hexyne D. 3-hexyne

1. A
2. B
3. C
4. D

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• Self Check Quizzes

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Study Guide 3
Section 21.3 Alkenes and Alkynes
Key Concepts

• Alkenes and alkynes are hydrocarbons that contain
  at least one double or triple bond, respectively.

• Alkenes and alkynes are nonpolar compounds with
  greater reactivity than alkanes but with other
  properties similar to those of alkanes.

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End of Section 21-3
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Section 21-4
Section 21.4 Hydrocarbon Isomers

• Distinguish between the two main categories of
  isomersstructural isomers and stereoisomers.

• Differentiate between geometric isomers with cis-
  and transprefixes.
• Describe the structural variation in molecules
  that results in optical isomers.

electromagnetic radiation transverse waves that
carry energy through empty space
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Section 21-4
Section 21.4 Hydrocarbon Isomers (cont.)
isomer structural isomer stereoisomer geometric
isomer
chirality asymmetric carbon optical
isomer optical rotation
Some hydrocarbons have the same molecular formula
but have different molecular structures.
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Section 21-4
Structural Isomers

• Isomers are two or more compounds that have the
  same molecular formula but different molecular
  structures.

• Structural isomers have the same chemical formula
  but their atoms are bonded in different
  arrangements.

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Section 21-4
Structural Isomers (cont.)

• There are two main classes of isomers structural
  isomers and stereoisomers.

• Structural isomers have different physical and
  chemical properties.
• More rounded shapes are less sticky
• The structure of a substance determines
  properties.

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Section 21-4
Stereoisomers

• Stereoisomers are isomers in which all atoms are
  bonded in the same order but are arranged
  differently in space.

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Section 21-4
Stereoisomers (cont.)

• Geometric isomers result from different
  arrangements of groups around a double bond.

• Cis means on the same side, and trans means
  across from.
• Geometric isomers have different physical and
  chemical properties.
• Cis but-2-ene trans but-2-ene
• Build these from the kit

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Section 21-4
Stereoisomers (cont.)
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• Cis-platin a cancer treatment drug

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Section 21-4
Chirality

• Louis Pasteur discovered two forms of
  crystallized tartaric acid.

• The forms were mirror images of each other called
  right and left-handed forms.
• The property in whicha molecule exists in right
  and left-handed forms is called chirality.

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Section 21-4
Optical Isomers

• Chirality occurs whenever a compound contains an
  asymmetric carbon.

• Asymmetric carbon is a carbon atom that has four
  different atoms or groups attached to it.
• The four groups can be arranged in two different
  ways.

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Section 21-4
Optical Isomers (cont.)

• Isomers that result from different arrangements
  of four different groups around a carbon atom
  represent the other class of stereoisomers,
  called optical isomers.

• Optical isomers have the same physical and
  chemical properties except in chemical reactions
  where chirality is important.

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Section 21-4
Optical Isomers (cont.)

• When polarized light passes through a solution
  containing an optical isomer, the plane of
  polarization is rotated to the right by the
  D-isomer and to the left by the L-isomer,
  producing and effect called optical rotation.

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Section 21-4
Optical Isomers (cont.)
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Section 21-4
Section 21.4 Assessment
What are two molecules with the same formula but
different structures called? A. isotopes
B. chiral C. isomers D. asymmetric

1. A
2. B
3. C
4. D

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Section 21-4
Section 21.4 Assessment
Which type of substances have the same physical
and chemical properties but produce different
optical rotations? A. isomers B. geometric
isomers C. isotopes D. optical isomers

1. A
2. B
3. C
4. D

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• Self Check Quizzes

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Study Guide 4
Section 21.4 Hydrocarbon Isomers
Key Concepts

• Isomers are two or more compounds with the same
  molecular formula but different molecular
  structures.

• Structural isomers differ in the order in which
  atoms are bonded to each other.
• Stereoisomers have all atoms bonded in the same
  order but arranged differently in space.

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End of Section 21-4
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Section 21-5
Section 21.5 Aromatic Hydrocarbons

• Compare and contrast the properties of aromatic
  and aliphatic hydrocarbons.

hybrid orbitals equivalent atomic orbitals that
form during bonding by the rearrangement of
valence electrons

• Explain what a carcinogen is, and list some
  examples.

aromatic compound aliphatic compound
Aromatic hydrocarbons are unusually stable
compounds with ring structures in which electrons
are shared by many atoms.
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Section 21-5
The Structure of Benzene

• Even by the middle of the 19th century,
  hydrocarbon ring structures remained unknown.

• Michael Faraday first isolated benzene in 1825.
• Chemists knew the formula was C6H6 and proposed
  several possible models which would have all be
  very reactive, but benzene is unusually stable.

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Section 21-5
The Structure of Benzene (cont.)

• German chemist Friederich Kekulé claimed to have
  had a dream in which he realized the flat,
  hexagonal shape ring structure for benzene.

• Kekulés structure explained some of benzene's
  properties, but not its lack of reactivity.

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Section 21-5
The Structure of Benzene (cont.)

• Linus Paulings hybrid orbital theory explained
  benzenes lack of reactivity.

• The double bonds in benzene are not fixed, but
  rather the electrons are delocalized and shared
  among all six carbon atoms.

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Section 21-5
Aromatic Compounds

• Organic compounds that contain benzene rings as
  part of their structure are called aromatic
  compounds.

• Aromatic was originally used because many benzene
  related compounds were found in pleasant smelling
  oils that came from plants and plant parts.

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Section 21-5
Aromatic Compounds (cont.)

• Aliphatic compounds are the alkane, alkene, and
  alkyne hydrocarbons, coming from the Greek word
  for fat because they were obtained by heating
  animal fat.

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• Sigma and pi bonding in benzene

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Section 21-5
Aromatic Compounds (cont.)

• Substituted benzene compounds are named in the
  same way as cyclic alkanes.

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Section 21-5
Aromatic Compounds (cont.)

• Many aromatic compounds were commonly used as
  industrial and laboratory solvents.

• Health risks linked to aromatics include
  respiratory ailments, liver problems, and damage
  to the nervous system.
• Some aromatic compounds cause cancer.

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Section 21-5
Section 21.5 Assessment
Aliphatic compounds were originally obtained from
____. A. fossil fuels B. animal fats C. plant
oils D. minerals

1. A
2. B
3. C
4. D

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Section 21-5
Section 21.5 Assessment
Which is NOT true of benzene? A. It is an
aromatic compound. B. It has a flat hexagonal
shape. C. The double bonds make it unstable.
D. It has delocalized electrons.

1. A
2. B
3. C
4. D

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• Self Check Quizzes

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Study Guide 5
Section 21.5 Aromatic Hydrocarbons
Key Concepts

• Aromatic hydrocarbons contain benzene rings as
  part of their molecular structures.

• The electrons in aromatic hydrocarbons are shared
  evenly over the entire benzene ring.

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End of Section 21-5
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Resources Menu
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104
Study Guide 1
Section 21.1 Introduction to Hydrocarbons
Key Concepts

• Organic compounds contain the element carbon,
  which is able to form straight chains and
  branched chains.

• Hydrocarbons are organic substances composed of
  carbon and hydrogen.
• The major sources of hydrocarbons are petroleum
  and natural gas.
• Petroleum can be separated into components by the
  process of fractional distillation.

105
Study Guide 2
Section 21.2 Alkanes
Key Concepts

• Alkanes contain only single bonds between carbon
  atoms.

• Alkanes and other organic compounds are best
  represented by structural formulas and can be
  named using systematic rules determined by the
  International Union of Pure and Applied Chemistry
  (IUPAC).
• Alkanes that contain hydrocarbon rings are called
  cyclic alkanes.

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Study Guide 3
Section 21.3 Alkenes and Alkynes
Key Concepts

• Alkenes and alkynes are hydrocarbons that contain
  at least one double or triple bond, respectively.

• Alkenes and alkynes are nonpolar compounds with
  greater reactivity than alkanes but with other
  properties similar to those of alkanes.

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Study Guide 4
Section 21.4 Hydrocarbon Isomers
Key Concepts

• Isomers are two or more compounds with the same
  molecular formula but different molecular
  structures.

• Structural isomers differ in the order in which
  atoms are bonded to each other.
• Stereoisomers have all atoms bonded in the same
  order but arranged differently in space.

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Study Guide 5
Section 21.5 Aromatic Hydrocarbons
Key Concepts

• Aromatic hydrocarbons contain benzene rings as
  part of their molecular structures.

• The electrons in aromatic hydrocarbons are shared
  evenly over the entire benzene ring.

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Chapter Assessment 1
Organic compounds must contain which elements?
A. carbon B. oxygen C. hydrogen D. nitrogen

1. A
2. B
3. C
4. D

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Chapter Assessment 2
Cyclohexane contains how many hydrogen atoms?
A. 6 B. 12 C. 14 D. 20

1. A
2. B
3. C
4. D

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Chapter Assessment 3
Which of the following has the greatest
reactivity? A. benzene B. hexane C. hexene
D. hexyne

1. A
2. B
3. C
4. D

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Chapter Assessment 4
A carbon bonded to four different groups is ____.
A. cyclic B. aromatic C. asymmetric
D. left-handed

1. A
2. B
3. C
4. D

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Chapter Assessment 5
Where were aromatic compounds originally obtained
from? A. fossil fuels B. plant oils, plant
parts, and spices C. animal fats D. minerals

1. A
2. B
3. C
4. D

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STP 1
Molecules that have the same formula and the
atoms are bonded in the same order but are
arranged differently in space, and have different
properties are ____. A. structural isomers
B. geometric isomers C. optical isomer
D. sterioisotopes

1. A
2. B
3. C
4. D

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STP 2
If n is the number of carbon atoms in a
hydrocarbon, what is the general formula of a
cyclic alkane? A. CnHn2 B. CnH2n2 C. CnHn
D. CnH2n

1. A
2. B
3. C
4. D

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STP 3
Which does NOT describe what happens as a liquid
freezes? A. The temperature of the system is
increased. B. Energy is released by the
system. C. The liquid is entering the solid
phase. D. The molecules begin to form a
lattice.

1. A
2. B
3. C
4. D

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STP 4
What is a series of compounds that differ from
one another by a repeating unit called?
A. heterogeneous series B. homologous series
C. straight-chain series D. branched-chain
series

1. A
2. B
3. C
4. D

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STP 5
What structural characteristic do all aromatic
compounds share? A. They are composed of
cyclohexane. B. They have a triple bond.
C. They contain a benzene ring. D. They
contain a cyclic alkane.

1. A
2. B
3. C
4. D

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CIM
Table 21.5 Examples of Alkenes Table
21.6 Examples of Alkynes Figure 21.17 Isomers of
Pentane Figure 21.25 Sigma- and Pi-bonding in
Benzene
143
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