3.6.9

Structural Isomers

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Structural Isomers

Structural isomers, including chain, positional and functional group isomers, are different molecules with the same molecular formula.

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Structural isomers

  • Structural isomers are different molecules with the same molecular formula.
  • Structural isomers have different structural formulas, but the same molecular formula.
  • Structural isomers have different physical properties
  • Structural isomers can be better understood by classifying them as chain, positional and functional group isomers.
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Chain isomers

  • Molecular formulas with four or more carbons can be represented by more than one structural formula by changing the amount of branching in the molecule.
  • The longer the carbon chain length the more possibilities there are.
  • The more branching the weaker the London dispersion forces and the lower the boiling point.
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Positional isomers

  • The functional group in a molecule can be moved to a different position to give positional isomers.
  • An example of this with C4H8 is shown above.
Illustrative background for Functional group isomers
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Functional group isomers

  • Molecules can also exist with the same molecular formula but with different functional groups.
  • Two typical examples of this are aldehydes with ketones and alkenes with cycloalkanes, shown above.

Jump to other topics

1Structure - Models of the Particulate of Matter

2Structure - Models of Bonding & Structure

3Structure - Classification of Matter

3.1The Periodic Table: Classification of Elements

3.2Periodic Trends

3.3Group 1 Alkali Metals

3.4Halogens

3.5Noble gases, group 18

3.6Functional Groups: Classification of Organic

3.7Functional Group Chemistry

3.8Alkanes

3.9Alcohols

3.10Halogenoalkanes

4Reactivity - What Drives Chemical Reaction?

5Reactivity - How Much, How Fast & How Far?

6Reactivity - The Mechanisms of Chemical Change

7Measurement, Data Processing & Analysis

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