General formulae
2 marks · EasyExplain how the presence of a functional group allows chemists to predict the chemical behaviour of organic compounds in the same homologous series.
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The functional group is the reactive part of the molecule. All compounds in a homologous series contain the same functional group, meaning they react in a similar way. This allows chemists to predict the chemical properties and reactions of all members of the series based on the functional group present.
Also accept: Because all members have the same functional group, they share similar chemical behaviour, so testing one compound helps predict how others in the series will react.
Common mistakes: Confusing physical properties with chemical properties
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Marking points
B1 · 1 mark · Mentions functional group is present in all members of the homologous series and determines their reactions.
B1 · 1 mark · States that this enables prediction of chemical behaviour or reactions for all members in the series.
Worked solution
All compounds in the same homologous series contain the same functional group. The functional group is responsible for the characteristic chemical reactions of those compounds. Therefore, if we know the reactions of the functional group, we can predict the chemical behaviour of other members of the series.