Structural isomerism in the alkanes
3 marks · NormalA hydrocarbon has the molecular formula C6H14. How many structural isomers are possible for C6H14? Show your reasoning.
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5 (±0)
Common mistakes: Including identical isomers by rotation; Forgetting one or more possible structures
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Marking points
M1 · 1 mark · Attempts to list or count different possible carbon backbone structures for C6.
M2 · 1 mark · Identifies and avoids counting duplicates by rotation or flipping.
A1 · 1 mark · Gives correct total: 5 structural isomers.
Worked solution
There are five structural isomers for C6H14 (hexane):
1. Hexane (straight chain) 2. 2-methylpentane 3. 3-methylpentane 4. 2,3-dimethylbutane 5. 2,2-dimethylbutane