There are two geometric isomers of 2-butene called cis-2-butene and trans-2-butene that differ only in whether the fourth carbon is on the same side or opposite side of the third carbon. While they have the same chemical formula of C4H8 and similar boiling points, they are different structures due to the inability of double bonds to rotate like single bonds can.

1. Geometric
Isomers
Sarah Gilbert

2. two isomers for 2-butene
• Cis-: “on the near side of”
• Trans-: “across, beyond, transverse”
• These are almost the same the only difference is
whether the fourth carbon added goes on the
same side as the third or not.
• Chemical formula is C4H8
• Average molar mass 56.11 g/mol

3. Cis-2-butene
• Same line
formula as
trans-2-butene

4. Trans-2-butene

5. Extra Fact
• This is the most simple alkene
showing cis/trans isomerism,
meaning it exists as two geometric
isomers.
• They are very difficult to separate by
distillation due to their close boiling
points

6. Summary
• Double bonds can not rotate due to the strength
of their bonds, but single bonds can because they
have less connection.
• Even though these two isomers have the same
formula they are very different structures with
different names.