Geometric isomers are compounds that have the same molecular formula and bonding but different spatial arrangements of atoms. They can exist as cis or trans isomers depending on whether substituents are on the same or opposite sides of a bond. Cis-2-butene and trans-2-butene were used as examples, with the hydrogen atoms having different orientations around the central double bond, resulting in shapes that are semi-hexagonal or zig-zag respectively.

1. GEOMETRIC ISOMERS
(CIS-TRANS)
Holden Montgomery

2. DEFINITION
• Portion D of the lab was focused on identifying and understanding what
are known as geometric isomers.
• Geometric isomers are two or more coordination compounds which
contain the same number and types of atoms and bonds, but which
have different spatial arrangements of the atoms.
(http://www.chem.purdue.edu/jmol/cchem/geomi.html)
• “cis” - molecular structure in which two particular atoms or groups lie on
the same side of a given plane in the molecule.
• “trans” - a molecular structure in which two particular atoms or groups lie
on opposite sides of a given plane in the molecule.

3. CIS-2-
BUTENE• This picture is of a molecule
of cis-2-butene. Cis-2-
butene is called this
because the molecules of
hydrogen attached to the
center two carbons are
located on the same side of
the molecule. This
orientation of the molecule
changes the shape from a
zig-zag to that of a semi-
hexagonal shape.

4. TRANS-2-
BUTENE• This is a picture of trans-2-
butene. This is the name for
this because the two
hydrogens attached to the
center two carbons are each
located on the opposite side
of the other. This
orientation changes the
shape of the molecule from
a semi-hexagonal shape to
a zig-zag shape

5. GEOMETRIC
ISOMERS FACT
• Geometric isomers differ in
physical properties such as
melting point and boiling
point.
(http://www.encyclopedia.c
om/science-and-
technology/chemistry/chem
istry-general/isomer)

6. SUMMARY
• Geometric isomers are a form of
stereoisomerism. Stereoisomers have the
same atoms and bonds but are 3-
dimensionally different. This difference in the
arrangements of the atoms results in different
properties. In the case for 2-butene, the
geometric isomerism is caused by the lack of
rotation around the center double bond.