Alkenes, Alkynes, and Aromatic Compounds

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Chapter 13

• Alkenes, Alkynes, and Aromatic Compounds

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Alkenes and Alkynes

• Alkanes are saturated hydrocarbons
• Alkenes and alkynes are unsaturated hydrocarbons
  contain multiple bonds
• Alkene At least 1 CC
• Alkyne At least 1 CC

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Naming Alkenes and Alkynes

• Rules similar to Alkanes
• Identify the parent compound longest chain that
  contains the double or triple bond
• Name the parent compound
• If alkene name the parent with the suffix ene
• If alkyne name the parent with the suffix yne

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Naming Alkenes and Alkynes

• The number of multiple bonds is indicated using a
  numerical prefix (diene 2 double bonds, triene
  3 double bonds, and so on) when there is more
  than one.

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Naming Alkenes and Alkynes

• Number the carbon atoms in the main chain,
  beginning at the end nearer the multiple bond. If
  the multiple bond is an equal distance from both
  ends, begin numbering at the end nearer the first
  branch point.

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Naming Alkenes and Alkynes

• Cyclic alkenes are called cycloalkenes. The
  double-bond carbon atoms in substituted
  cycloalkenes are numbered 1 and 2 so as to give
  the first substituent the lower number

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Naming Alkenes and Alkynes

• Write the full name.
• Assign numbers to the branching substituents, and
  list the substituents alphabetically.
• Use commas to separate numbers and hyphens to
  separate words from numbers.
• Indicate the position of the multiple bond in the
  chain by giving the number of the first
  multiple-bonded carbon. If more than one double
  bond is present, identify the position of each
  and use the appropriate name ending (for example,
  1,3-butadiene and 1,3,6-heptatriene).

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Cis-Trans Isomerism

• Shape
• Alkanes tetrahedral
• Alkenes trigonal planar
• Alkynes Linear
• Alkanes contain single bonds which allowed for
  easy rotation many conformers
• Alkenes and Alkynes the formation of the multiple
  bond inhibits rotation
• Very specific isomers

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Cis-Trans Isomerism

• Cistrans isomerism occurs in an alkene whenever
  each double-bond carbon is bonded to two
  different substituent groups. If one of the
  double-bond carbons is attached to two identical
  groups, cistrans isomerism is not possible.

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Cis-Trans Isomerism
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Properties of Alkenes and Alkynes

• Like the alkanes, alkenes and alkynes are
• Nonpolar insoluble in water soluble in nonpolar
  organic solvents less dense than water
• Flammable nontoxic
• Unlike the alkanes
• Alkenes display cistrans isomerism when each
  double-bond carbon atom has different
  substituents
• Alkenes and alkynes are chemically reactive at
  the multiple bond

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Types of Organic Reactions

• Addition Reactions

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Types of Reactions

• Elimination Reactions

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Types of Reactions

• Substitution Reactions

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Types of Reactions

• Rearrangement Reactions

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Reactions of Alkenes and Alkynes

• Most common reaction of alkenes and alkynes are
  addition reactions
• Hydrogenation
• Halogenation
• Hydrohalogenation
• Hydration

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Reactions of Alkenes and Alkynes

• Hydrogenation adds Hs to each carbon making up
  the multiple bond forming a saturated alkane

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Reactions of Alkenes and Alkynes

• Halogenation adds a halogen to each carbon
  present in the multiple bond

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Reactions of Alkenes and Alkynes

• Hydrohalogenation adds H to one carbon and a
  halogen to the other carbon making up the
  multiple bond
• Markovnikovs rule When adding different
  substituents to the Cs of a multiple bond the H
  goes on the C with the most Hs in the multiple
  bond

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Reactions of Alkenes and Alkynes

• Hydration Adds a water molecule to the double
  bond. The OH is attached to the C with the
  fewest Hs and the H is attached to the C with
  the most Hs.

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How Alkene Addition Reactions Occur

• Reaction mechanism A description of the
  individual steps by which old bonds are broken
  and new bonds are formed in a reaction

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Alkene Polymers

• A polymer is a large molecule formed by the
  repetitive bonding together of many smaller
  molecules called monomers.

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Alkene Polymers

• Adding an initiator to an alkene results in a
  break in the double bond, yielding a reactive
  intermediate that contains an unpaired electron.

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Aromatic Compounds and the Structure of Benzene

• Aromatic compound any compound that contains a
  benzene ring

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Aromatic Compounds and the Structure of Benzene

• Aromatic compounds are much less reactive than
  alkenes

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Aromatic Compounds and the Structure of Benzene

• Simple aromatic hydrocarbons like benzene are
  nonpolar, insoluble in water, volatile, and
  flammable. Unlike alkanes and alkenes, however,
  several aromatic hydrocarbons are toxic.

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Naming Aromatic Compounds

• Substituted benzenes are named using -benzene as
  the parent.
• No number is needed for monosubstituted benzenes
  because all the ring positions are identical.

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Naming Aromatic Compounds

• Disubstituted aromatic compounds are named using
  one of the prefixes ortho-, meta-, or para-.
• ortho- 1,2 relationship on the ring.
• meta- 1,3 relationship on the ring.
• para- 1,4 relationship on the ring.
• Name in alphabetical order

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Naming Aromatic Compounds

• Many substituted aromatic compounds have common
  names in addition to their systematic names.

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Naming Aromatic Compounds

• Occasionally, the benzene ring itself may be
  considered a substituent group attached to
  another parent compound. When this happens, the
  name phenyl is used for the unit

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Reactions of Aromatic Compounds

• Aromatic Compounds typically follow
  substitution reactions
• Nitration
• Halogenation
• Sulfonation

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Reactions of Aromatic Compounds

• Nitration replaces a H for NO2 using nitric
  acid and sulfuric acid

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Reactions of Aromatic Compou

• Halogenation replacement of H with a halogen

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Reactions of Aromatic Compounds

• Sulfonation replaces a H with HSO3

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Homework

• 13.23, 13.24, 13.25, 13.26, 13.27, 13.29, 13.34,
  13.35, 13.36, 13.37, 13.38, 13.39, 13.40, 13.41,
  13.48, 13.50, 13.51, 13.56, 13.57, 13.58, 13.59,
  13.60, 13.61, 13.63, 13.64, 13.66, 13.67, 13.80,
  13.81, 13.82, 13.84, 13.85, 13.86, 13.89, 13.90,
  13.91