Chemistry · General chemistry II · Worked example
Name cis- and trans-2-butene
CH₃CH=CHCH₃ can be drawn with its two methyl groups on the same side of the double bond or on opposite sides. Name each.
Name the chain
Four carbons with the double bond starting at carbon 2: 2-butene.
Check for cis/trans
Each double-bond carbon has one methyl group and one hydrogen, so the arrangement matters.
Read the drawing
Methyl groups on the same side of the double bond: cis. On opposite sides: trans.
Result
cis-2-butene (methyl groups on the same side) and trans-2-butene (opposite sides).
Your turn
Does CH₃CH=C(CH₃)₂ have cis and trans forms?
Show the answer and explanation
No.
One double-bond carbon carries two identical methyl groups, so swapping sides gives the same compound: 2-methyl-2-butene.
Keep exploring
Draw 2-butene in the Skeletal tool, choose Name, then flip one methyl group across the double bond and choose Name again.
Return to the concept →Sources and scope
Authored study material. Tool results depend on the stated inputs and model assumptions.
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Draw 2-butene in the Skeletal tool Open worked example on a board Organic nomenclature in Chemistry ReferenceYour existing work stays on this device. Examples open as editable copies.