Aromatic Compounds Classification
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Questions and Answers

What differentiates aromatic compounds from aliphatic compounds?

  • Aromatic compounds have less hydrogen compared to aliphatic compounds. (correct)
  • Aromatic compounds are always liquid at room temperature.
  • Aromatic compounds are more reactive than aliphatic compounds.
  • Aromatic compounds are exclusively derived from alkanes.

    • Who was the first to recognize Benzene as the first aromatic compound?

  • Mendeleev
  • Dalton
  • Kekulé (correct)
  • Rutherford

    • How did Kekulé describe the two different ways to draw the structure of '1,2-dibromobenzene'?

  • As isomers with distinct properties.
  • As identical structures with no differences.
  • As completely unrelated structures.
  • As two sides of the same coin, always changing. (correct)

    • How do we differentiate the naming of aromatic compounds from chain compounds?

    <p>Naming aromatic compounds is more complex and often has multiple acceptable names.</p> Signup and view all the answers

    What structural feature is common to all aromatic compounds?

    <p>They are derived from benzene and have a ring with six carbon atoms.</p> Signup and view all the answers

    Why is the numbering of substituents on a benzene ring important?

    <p>To give the substituents the smallest numbers in the name</p> Signup and view all the answers

    Which compound would be named 'xylene'?

    <p>Benzene with two methyl groups attached</p> Signup and view all the answers

    In alkyl group naming, when is phenyl considered as the parent compound?

    <p>When phenyl is attached to an unsaturated chain</p> Signup and view all the answers

    How does benzene react differently compared to unsaturated compounds when reacting with bromine?

    <p>Benzene substitutes with bromine instead of adding it</p> Signup and view all the answers

    Study Notes

    Aromatic Compounds

    • Aromatic compounds have common names that are used as formal names in the IUPAC system, e.g., Toluene, phenol, aniline.
    • Aromatic compounds with multiple groups attached to the benzene ring use "ortho" (o-), "meta" (m-), and "para" (p-) to show the location of the groups, or numbering.

    Numbering Aromatic Compounds

    • The first group attached to the ring is at position 1.
    • Other positions are numbered 2 to 6, and can be counted in either direction.
    • The numbering system is chosen to give the smallest numbers in the name.

    Nomenclature of Aromatic Compounds

    • Aromatic compounds with only one group attached to the benzene ring consider benzene as the parent and start naming with the substituent as a prefix.
    • If there are more than two groups on the benzene ring, numbers are used to show their location.
    • If there are more than two different groups, they are listed in alphabetical order.

    Phenyl Group

    • The phenyl group (C6H5-) is formed by removing one hydrogen from benzene.
    • When phenyl is attached to a saturated chain, it must have more carbons than the aromatic compound to be used as the parent.
    • When phenyl is attached to an unsaturated chain, the chain length doesn't matter, and the unsaturated compound is used as the parent, with the aromatic compound as a substituent.

    General Reactions of Aromatic Compounds

    • Aromatic compounds do not react like unsaturated compounds, e.g., alkenes.
    • Benzene reacts with bromine, but not by addition, rather by substitution, forming only one mono-bromobenzene.

    Aromaticity

    • Benzene is said to be aromatic, and any molecule with the same characteristics is also aromatic.
    • Aromatic compounds have four main characteristics:
      • Cyclic compounds that are planar.
      • They must have a conjugated system.
      • They must have high stabilization energy.
      • Prefer substitution reactions over addition.

    Theories of Aromaticity

    • There are two theories to explain why benzene has higher energy and less stability than expected:
      • Resonance theory.
      • Molecular Orbital (MO) theory.

    Classification of Organic Compounds

    • Organic compounds are classified into two categories:
      • Aliphatic: means "fat-like", reacts like alkane, alkene, and alkyne.
      • Aromatic: means the compound has less hydrogen than aliphatic compounds, and refers to "scent or smell or fragrant".

    Kekulé's Contribution

    • Kekulé was the first to recognize benzene as an aromatic compound.
    • He found two different ways to draw the structure of "1,2-dibromobenzene", but only one was found in experiments.
    • He proposed the concept of resonance hybrid structure, like a blend of two structures.

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    Description

    Learn about the classification of organic compounds into aliphatic and aromatic categories. Understand the differences between aliphatic and aromatic compounds, with a focus on the properties and characteristics of aromatic compounds like benzene.

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