General formulae
2 marks · HardState what is meant by the term 'functional group' in organic chemistry. Explain why functional groups are important when studying homologous series.
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A functional group is an atom or group of atoms responsible for the characteristic chemical reactions of a compound. Functional groups determine the chemical properties shared by all compounds in the same homologous series.
Also accept: Functional group: an atom or group of atoms that determines the chemical properties of an organic compound. They allow compounds in the same homologous series to have similar reactions.
Common mistakes: Saying only that it's a 'group of atoms', without mentioning effect on chemical properties; Defining by example only, without mentioning its role
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Marking points
B1 · 1 mark · States that a functional group is an atom or group of atoms that determines the chemical properties of the compound.
B2 · 1 mark · Explains that functional groups are important because they give all members of a homologous series similar chemical properties / determine reactions.
Worked solution
A functional group is an atom or group of atoms responsible for the characteristic chemical properties of a compound. Functional groups are important because all members of a homologous series share the same functional group, so they have similar chemical reactions.