Coding for the type of compound
3 marks · NormalExplain how the name but-2-ene shows both the number of carbon atoms and the position of the double bond in the molecule.
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‘But’ means four carbon atoms. The ‘2’ in but-2-ene shows the double bond starts on the second carbon. The ‘ene’ ending tells us it has a carbon–carbon double bond.
Also accept: ‘But’ = 4 carbons, ‘2’ = position of double bond, ‘ene’ = double bond
Common mistakes: Saying the double bond is between carbon 1 and 2
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Marking points
B1 · 1 mark · Correctly states that 'but' means 4 carbon atoms
B2 · 1 mark · Correctly explains the '2' means double bond is at the second carbon
B3 · 1 mark · States the 'ene' ending means a C=C double bond is present
Worked solution
‘But’ in the name shows the molecule has four carbon atoms. The number ‘2’ tells us the double bond starts at the second carbon. The ending ‘ene’ shows there is a carbon–carbon double bond.