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									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 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
Section 21.1 Introduction to Hydrocarbons
(cont.)



organic compound           unsaturated hydrocarbon
hydrocarbon                fractional distillation
saturated hydrocarbon      cracking


              Hydrocarbons are carbon-containing
              organic compounds that provide a
              source of energy and raw materials.
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.
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.
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.
Hydrocarbons

• The simplest organic compounds are
  hydrocarbons, which consist of only the
  elements carbon and hydrogen.
• There are thousands of hydrocarbons.
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.
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.
Refining Hydrocarbons (cont.)
Refining Hydrocarbons (cont.)



• Heavier fractions are converted to gasoline or
  other lighter fractions by a process called
  cracking.
Refining Hydrocarbons (cont.)

• Natural gas 1-4 carbons
• Gasoline is not a pure substance.
• Most molecules have 5 to 12 carbons.
• octane rating system.
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
                                             A.    A
C. saturation
                                             B.    B
D. bonding                                   C.    C
                                   0%   0%    0%    0%

                                             D.    D
                               A




                                        B




                                              C




                                                    D
Section 21.1 Assessment

What is a hydrocarbon that contains only
single bonds called?
A. unsaturated
B. organic
C. saturated                                A. A
D. fully bonded                             B. B
                                            C. C
                                    0%   0%  0% 0%
                                            D. D
                                A




                                         B




                                             C




                                                 D
• quiz
                 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.
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
Section 21.2 Alkanes (cont.)

alkane
homologous series
parent chain
substituent group
cyclic hydrocarbon
cycloalkane

               Alkanes are hydrocarbons that contain
               only single bonds.
Straight-Chain Alkanes

• Alkanes are hydrocarbons that have only
  single bonds between atoms.
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.
Straight-Chain Alkanes (cont.)
Branched-Chain Alkanes

• Carbon atoms can bond to one, two, three,
  or four other carbon atoms making a
  variety of chains possible.
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
• 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.
• C7H16
Branched-Chain Alkanes (cont.)
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.
Branched-Chain Alkanes (cont.)

• Naming branched-chain alkanes
 − Write the entire name, using hyphens to separate
   numbers from words and commas to separate
   numbers.
• Isomers of pentane
• Draw all the isomers of hexane
• Make up each with the kit provided.
• Do question 1 to 4 page 705
• Answer to 1 & 2 on page 950
• 3) 2-methylpentane 2,2-dimethylpropane
Cycloalkanes

• An organic compound that contains a
  hydrocarbon ring is called a cyclic
  hydrocarbon.
• Cyclic hydrocarbons with
  only single bonds are called
  cycloalkanes.
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.
• Do questions 10, 11 page 708
• Answers on page 950
Properties of Alkanes

• Structure affects molecular properties.
• Alkanes are not polar and are good solvents
  for other nonpolar molecules.
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.
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.
• Do questions 12 and 13 page 710
• A) 1-ethyl-2,4,5-trimethylcyclohexane
• B) 1,2-dipropylcyclopentane
•   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
Section 21.2 Assessment

What is a cyclic alkane with no
substituents groups and 6 carbon atoms?
A. heptane
B. cycloheptane
C. cyclohexane                            A. A
D. cyclobutane                            B. B
                                          C. C
                                  0%   0%  0% 0%
                                          D. D
                              A




                                       B




                                           C




                                               D
Section 21.2 Assessment

Alkanes contain how many double
bonds?
A. greater than 2
B. 2
C. 1                                     A. A
D. 0                                     B. B
                                         C. C
                                 0%   0%  0% 0%
                                         D. D
                             A




                                      B




                                          C




                                              D
• Self Check Quizzes
                 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.
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
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.
Alkenes

• Unsaturated hydrocarbons that contain at
  least one or more double covalent bonds
  between carbon atoms are called alkenes.
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.
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.
• Examples of alkenes
• Do problem18 and 19 page 714
• Answers on page 950
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.
Alkynes

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

• Straight-chain and branched-chain alkynes
  are named in the same way as alkenes,
  except the ending is –yne.
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.
• Examples of alkynes
•   Do problems 21 page 716
•   1-butyne
•   5-methyl-3-heptene
•   4-methyl-1,3-pentadiene
•   2,3-dimethyl-2-butene
Section 21.3 Assessment

Which of the following is generally the
most reactive?
A. cycloalkanes
B. alkanes
C. alkenes                                   A. A
D. alkynes                                   B. B
                                             C. C
                                     0%   0%  0% 0%
                                             D. D
                                 A




                                          B




                                              C




                                                  D
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                                A. A
C. 2-hexyne
                                           B. B
                                           C. C
D. 3-hexyne                        0%   0%  0% 0%
                                           D. D
                               A




                                        B




                                            C




                                                D
• Self Check Quizzes
                  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.
Section 21.4 Hydrocarbon Isomers

• Distinguish between the two main categories of
  isomers—structural 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
Section 21.4 Hydrocarbon Isomers (cont.)

isomer                     chirality
structural isomer          asymmetric carbon
stereoisomer               optical isomer
geometric isomer           optical rotation



             Some hydrocarbons have the same
             molecular formula but have different
             molecular structures.
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.
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.
Stereoisomers

• Stereoisomers are isomers in which all
  atoms are bonded in the same order but
  are arranged differently in space.
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
Stereoisomers (cont.)
• Cis-platin a cancer treatment drug
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 which
  a molecule exists in
  right and left-handed
  forms is called
  chirality.
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.
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.
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.
Optical Isomers (cont.)
Section 21.4 Assessment

What are two molecules with the same
formula but different structures called?
A. isotopes
B. chiral
C. isomers                                   A. A
D. asymmetric                                B. B
                                             C. C
                                     0%   0%  0% 0%
                                             D. D
                                 A




                                          B




                                              C




                                                  D
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
                                          A. A
C. isotopes
                                          B. B
D. optical isomers                        C. C
                                  0%   0%  0% 0%
                                          D. D
                              A




                                       B




                                           C




                                               D
• Self Check Quizzes
                  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.
Section 21.5 Aromatic Hydrocarbons

• Compare and contrast       hybrid orbitals: equivalent
  the properties of          atomic orbitals that form
  aromatic and aliphatic     during bonding by the
  hydrocarbons.              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.
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.
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.
• Kekulé’s structure explained some of
  benzene's properties, but not its lack of
  reactivity.
The Structure of Benzene (cont.)

• Linus Pauling’s 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.
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.
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.
• Sigma and pi bonding in benzene
Aromatic Compounds (cont.)

• Substituted benzene compounds are
  named in the same way as cyclic alkanes.
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.
Section 21.5 Assessment

Aliphatic compounds were originally
obtained from ____.
A. fossil fuels
B. animal fats
C. plant oils                              A. A
D. minerals                                B. B
                                           C. C
                                   0%   0%  0% 0%
                                           D. D
                               A




                                        B




                                            C




                                                D
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.                                    A. A
D. It has delocalized electrons.                B. B
                                                C. C
                                        0%   0%  0% 0%
                                                D. D
                                    A




                                             B




                                                 C




                                                     D
• Self Check Quizzes
                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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                 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.
                 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.
                  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.
                  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.
                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.
Organic compounds must contain which
elements?
A. carbon
B. oxygen
C. hydrogen                              A. A
D. nitrogen                              B. B
                                         C. C
                                 0%   0%  0% 0%
                                         D. D
                             A




                                      B




                                          C




                                              D
Cyclohexane contains how many
hydrogen atoms?
A. 6
B. 12
C. 14                                   A. A
D. 20                                   B. B
                                        C. C
                                0%   0%  0% 0%
                                        D. D
                            A




                                     B




                                         C




                                             D
Which of the following has the greatest
reactivity?
A. benzene
B. hexane
C. hexene                                   A. A
D. hexyne                                   B. B
                                            C. C
                                    0%   0%  0% 0%
                                            D. D
                                A




                                         B




                                             C




                                                 D
A carbon bonded to four different groups
is ____.
A. cyclic
B. aromatic
C. asymmetric                               A. A
D. left-handed                              B. B
                                            C. C
                                    0%   0%  0% 0%
                                            D. D
                                A




                                         B




                                             C




                                                 D
Where were aromatic compounds
originally obtained from?
A. fossil fuels
B. plant oils, plant parts, and spices
C. animal fats                                   A. A
D. minerals                                      B. B
                                                 C. C
                                         0%   0%  0% 0%
                                                 D. D
                                     A




                                              B




                                                  C




                                                      D
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                        A. A
C. optical isomer
                                            B. B
                                            C. C
D. sterioisotopes                   0%   0%  0% 0%
                                            D. D
                                A




                                         B




                                             C




                                                 D
If n is the number of carbon atoms in a
hydrocarbon, what is the general formula
of a cyclic alkane?
A. CnHn+2
B. CnH2n+2
                                            A. A
C. CnHn
                                            B. B
D. CnH2n                                    C. C
                                    0%   0%  0% 0%
                                            D. D
                                A




                                         B




                                             C




                                                 D
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.                                     A. A
C. The liquid is entering the
                                               B. B
   solid phase.                                C. C
                                       0%   0%  0% 0%

D. The molecules begin to form                 D. D
                                   A




                                            B




                                                C




                                                    D
   a lattice.
What is a series of compounds that differ
from one another by a repeating unit
called?
A. heterogeneous series
B. homologous series
                                            A. A
C. straight-chain series
                                            B. B
D. branched-chain series                    C. C
                                    0%   0%  0% 0%
                                            D. D
                                A




                                         B




                                             C




                                                 D
What structural characteristic do all
aromatic compounds share?
A. They are composed of
   cyclohexane.
B. They have a triple bond.
                                              A. A
C. They contain a benzene
   ring.
                                              B. B
                                              C. C
D. They contain a cyclic              0%   0%  0% 0%

   alkane.                                    D. D
                                  A




                                           B




                                               C




                                                   D
Click on an image to enlarge.
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
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