Chapter 12.5 Aromatic Hydrocarbons

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Chapter 12.5Aromatic Hydrocarbons
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Aromatic Compounds and Benzene

• Aromatic compounds contain benzene.
• Benzene, C6H6 , is represented as a six carbon
  ring with 3 double bonds.
• Two possible isomers can be drawn to show
  benzene in this form.

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Aromatic Compounds and Benzene

• The name aromatic came from many of the first
  examples discovered were pleasant smelling
• Many aromatics that have recently been discovered
  are not pleasant smelling, though
• The most common aromatic ring is benzene which
  includes 6 Carbons and 6 Hydrogens--it is highly
  unsaturated

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Aromatic Compounds and Benzene

• Strangely, aromatics do not undergo the same
  kinds of reactions as alkenes and alkynes
• The benzene ring is planar and hexagonal
• The three double bonds in benzene are shared
  equally between the six carbons. We say that the
  double bonds are delocalized
• Benzene is unusually stable and resists most
  reactions

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Benzene Structure

• The structures for benzene can also be written
  as a single structure where the alternating
  double bonds are written as a circle within the
  ring.
• Benzene
• structure

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Aromatic Compounds in Nature and Health

• Many aromatic compounds are common in nature and
  in medicine.

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Naming Aromatic Compounds

• Aromatic compounds are named with benzene as the
  parent chain. One side group is named in front of
  the name benzene.
• methylbenzene chlorobenzene
• (toluene)

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You Try These!

• Name the following aromatic compounds.

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Answers to You Try These!

• Name the following aromatic compounds.

Bromobenzene Ethylbenzene
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Common Aromatic Compounds You Should Know
Nitrobenzene
Toluene
Aniline
Phenol
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Naming Aromatic Compounds

• When two groups are attached to benzene, the
  ring is numbered to give the lower numbers to the
  side groups. The prefixes ortho (1,2), meta
  (1,3) and para (1,4) are also used.

ortho-dimethylbenzene meta-dichlorobenzene para-ch
loromethylbenzene
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Some Common Names

• Some substituted benzene rings also use a common
  name. Naming with additional side groups then
  uses the ortho-, meta-, para- system. Common
  naming utilizes the prefixes, while IUPAC naming
  uses the numbers.

Toluene m-chlorotoluene
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Some More Common Names
Phenol p-nitrophenol
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Other Common Aromatic Compounds You Should Know
CH3
Xylene
CH3
OH
Cresol
CH3
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You Try These!

• Select the names for each structure
• 1. Chlorocyclohexane
• 2. Chlorobenzene
• 3. 1-chlorobenzene
• 1. Meta-methyltoluene
• 2. Meta-dimethylbenzene
• 3. 1,3-dimethylbenzene

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Answers to You Try These!

• Select the names for each structure
• 2. Chlorobenzene
• 1. Meta-methyltoluene
• 2. Meta-dimethylbenzene
• 3. 1,3-dimethylbenzene

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You Try these!

• Write the structural formulas for each of the
  following
• A. 1-bromo-3-methylbenzene
• B. Ortho-chlorotoluene

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Answers to You Try These!

• Write the structural formulas for each of the
  following
• A. 1-bromo-3-methylbenzene
• B. Ortho-chlorotoluene

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Homework Assignment

• 3rd Ed Pg. 345 11 12
• (use list of common names on
• page 343-344)
• 4th Ed Pg. 354 13 14
• (use list of common names on
• page 352)
• Due Tomorrow!