Structural isomerism in the alkanes
2 marks · NormalExplain what is meant by the term 'structural isomers' with reference to alkanes.
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Structural isomers are molecules with the same molecular formula but different structural formulae; in alkanes, this means carbon atoms are joined in different arrangements (branched or unbranched chains).
Also accept: Molecules having the same molecular formula but atoms connected differently; Compounds with the same number of each element but different connections of atoms
Common mistakes: Confusing isomers with isotopes; Saying only that they have different formulas
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Marking points
B1 · 1 mark · States that structural isomers have the same molecular formula.
B2 · 1 mark · States that structural isomers have different structures/structural formulae or carbon arrangements.
Worked solution
Structural isomers are molecules that have the same molecular formula but a different structural formula; this means the atoms are connected in different arrangements. For alkanes, this means the carbon atoms can form straight or branched chains.