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Homologous Series

A homologous series is a set of compounds with the same functional group. Members of a homologous series have very similar properties because they have the same functional group.

General formulae

General formulae

  • Every homologous series has its own general formula:
    • E.g. Alkanes: CnH2n+2
    • E.g. Alkenes: CnH2n
    • E.g. Alcohols: CnH2n+2O
  • The general formula gives the molecular formula for each compound in the homologous series.
  • Different molecules in the series differ mainly in the length of their aliphatic chains.
    • Aliphatic chains are carbon chains that do not have a benzene ring.
Functional groups

Functional groups

  • A functional group is a group of atoms that characterise the chemistry of a molecule. Functional groups cause specific reactions to happen with certain reagents.
  • Examples of functional groups are:
    • Hydroxyl group (-OH).
    • Carboxylic acid group (-COOH) (pictured).
    • Carbon-carbon double bond (C=C).
Alkyl group

Alkyl group

  • An alkyl group is a saturated hydrocarbon chain attached to a molecule.
    • The letter R can be used to represent alkyl groups.
Aliphatic

Aliphatic

  • Aliphatic compounds contain carbon chains that do not involve a benzene ring.
  • Aliphatic chains can be saturated, unsaturated, straight, branched or circular.
Alicyclic

Alicyclic

  • Alicyclic compounds are aliphatic compounds that have non-aromatic rings but no side chains.
    • E.g. Cyclohexane.
Aromatic

Aromatic

  • Aromatic compounds contain at least one benzene ring.
  • Benzene rings tend to make these compounds smell.
    • This is why these compounds are described as aromatic.
Saturated/unsaturated

Saturated/unsaturated

  • Saturated compounds contain single bonds only between carbon atoms (C-C).
  • Unsaturated compounds contain at least one different carbon-carbon bond such as C=C or an aromatic ring.
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Principles of Science I

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Structure & Bonding

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Cell Structure & Function

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1.6

Working with Waves

1.7

Waves in Communication

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Practical Scientific Procedures and Techniques

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Science Investigation Skills

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Principles of Science II

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Extracting Elements

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Relating Properties to use of Substances

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Organic Chemistry

4.4

Energy Changes in Industry

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4.6

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Contemporary Issues in Science

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