Introduction to Geometrical Isomerism

1. Introduction to
Geometrical
Isomerism
Geometrical isomerism, also known as cis-trans isomerism, is a type of
stereoisomerism that arises when a molecule contains a rigid, planar
structure with restricted rotation around a carbon-carbon double bond.
This results in the possibility of different spatial arrangements of the
substituents.

2. Definition of Geometrical Isomerism
Geometrical isomerism occurs when two molecules have the same molecular formula and connectivity,
but differ in the spatial arrangement of their substituents around a carbon-carbon double bond. This
results in distinct physical and chemical properties between the isomers.

3. Conditions for Geometrical Isomerism
1 Rigid, Planar
Structure
The molecule must have
a carbon-carbon double
bond with a rigid, planar
structure that prevents
free rotation.
2 Different
Substituents
The two substituents
attached to each carbon
of the double bond must
be different.
3 Restricted
Rotation
The rotation around the
carbon-carbon double
bond must be restricted,
preventing the
substituents from
switching positions.

4. Types of Geometrical Isomers
Cis Isomers
In cis isomers, the same
substituents are on the same
side of the double bond.
Trans Isomers
In trans isomers, the same
substituents are on opposite
sides of the double bond.
E-Z Isomers
E-Z isomerism is a system
used to designate the
stereochemistry of organic
compounds with a carbon-
carbon double bond.

5. Cis-Trans Isomerism
1 Cis Isomers
In cis isomers, the substituents are on the same side of the double bond.
2 Trans Isomers
In trans isomers, the substituents are on opposite sides of the double bond.
3 Interconversion
Cis-trans isomers cannot be interconverted without breaking the double
bond.

6. E-Z Isomerism
Priority Groups
E-Z isomerism considers the
priority of the substituents
attached to the carbon-carbon
double bond.
Directional Orientation
The substituents are assigned
E (from the German
"entgegen") or Z (from the
German "zusammen") based
on their relative positions.
Double Bond Geometry
E isomers have the higher
priority substituents on
opposite sides, while Z isomers
have them on the same side.

7. Factors Affecting Geometrical
Isomerism
Steric Hindrance
Large substituents on the
carbon-carbon double bond
can cause steric hindrance,
favoring the trans isomer.
Electronegativity
The relative electronegativity
of the substituents can also
influence the stability and
formation of the isomers.
Solvent Effects
The polarity of the solvent
can affect the solubility and
stability of the isomers,
potentially shifting the
equilibrium.

8. Importance and Applications of
Geometrical Isomerism
Pharmaceutical Industry
Geometrical isomerism is crucial in the
development of new drugs, as the isomers
can have vastly different biological activities.
Materials Science
Geometrical isomers can exhibit different
physical properties, such as melting and
boiling points, which is important in the
design of new materials.
Organic Synthesis
Understanding and controlling geometrical
isomerism is essential in the synthesis of
complex organic molecules with desired
properties.
Environmental Impact
Geometrical isomers can have different
environmental impacts, such as toxicity and
biodegradability, which is important in
environmental chemistry and regulation.