Isomerism
Contents
• Isomerism
• Structural isomerism
• Chain isomerism
• Positional isomerism
• Functional isomerism
• Metamerism
• Tautomerism
• Stereo isomerism
• Geometrical isomerism
• Optical isomerism
Learning
Objectives
At the end of this lecture, student will be able to
• Define the term isomerism
• Differentiate between the different types of isomerism
with examples
Isomerism
Definition
• Two or more compounds with same molecular formula but
different physical or chemical properties
• Isomers
Types of isomerism
• Structural isomerism
• Stereo isomerism
Structural isomerism
• Two or more compounds with same molecular formula and
different structural formula
Stereo isomerism
• Two or more compounds with same structural formula and
different configuration
TYPES OF ISOMERISM
Chain Isomerism
• Difference in the nature of the carbon chain
• Examples
Position isomerism
• Position of the substituent atom or group or unsaturated
linkage
• Examples
Functional isomerism
• Difference in the nature of the functional group
• Examples
Metamerism
• Nature of the alkyl groups attached to the same functional
group
• Example
CH3—CH2—NH—CH2—CH3
CH3—CH2—CH2—NH—CH3
Keto enol tautomerism
– Tautomers
– Keto tautomer – more stable
Keto enol tautomerism
• Examples
Geometrical isomerism
• Geometrical isomers
• Cis isomers
• Trans isomers
Optical isomerism
• Laevo isomer
• Dextro isomer
Summary
• Isomerism is the phenomenon in which two or more compounds
have the same molecular formula but different properties
• Structural isomers have same molecular formula but
different structural formula
• Stereo isomers have same molecular formula but atoms
occupy different positions in space