Structural Isomers
Chemistry: IB Diploma Higher Level, topic 3.6.9
Structural Isomers
Structural isomers, including chain, positional and functional group isomers, are different molecules with the same molecular formula.
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.
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.
Chain isomers
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.
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.
Test yourself on Structural Isomers
Which of these is NOT an example of structural isomerism?
Which of these statements is NOT correct?