Chemistry · General chemistry II · Worked example
Name a branched alkene
Name CH₃CH₂C(CH₃)=C(CH₃)CH₂CH₃.
Find the chain with the double bond
The longest chain containing the C=C runs from one ethyl end, across the double bond, to the other ethyl end: six carbons, so the parent is hexene.
Number the chain
The double bond starts at carbon 3 from either end, so both directions give 3.
Place the branches
The two methyl groups are on carbons 3 and 4, from either end.
Write the name
Two methyl groups are 3,4-dimethyl, and the bond’s number goes before the parent name.
Result
3,4-dimethyl-3-hexene (today’s IUPAC form: 3,4-dimethylhex-3-ene).
Your turn
Name HC≡CCH₂CH₃.
Show the answer and explanation
1-butyne.
Four carbons with a triple bond starting at carbon 1 (but-1-yne in today’s IUPAC form). Numbering from the other end would put it at 3.
Keep exploring
Draw it with the name as its target and turn Check on. Choose Name to see the steps: cis/trans is left out, because each double-bond carbon carries two groups and needs E/Z rules instead.
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Open the example inputs, change a value and keep a useful result on your board.
Draw it and check the name See 1-butyne in every representation Open worked example on a board Organic nomenclature in Chemistry ReferenceYour existing work stays on this device. Examples open as editable copies.