This document discusses different types of structural isomers: 1) Structural isomers have the same molecular formula but different structural formulas, meaning different bond patterns or arrangements of atoms. 2) Types of structural isomers include chain isomers, positional isomers, functional isomers, metamers, and tautomers. 3) Tautomers are functional isomers that exist in rapid equilibrium in solution and differ in the position of a hydrogen atom on an alpha carbon, allowing interconversion through catalysis. Only the more stable tautomeric form is considered an isomer.

1. STRUCTURE OF ISOMERS
Presented by
manka marycleopha.
2nd MSc microbiology

2. STRUCTURAL OF ISOMERS
Introduction
 Structural Isomers: Isomers ,which have same molecular
formula, but different structural formula are called
structural isomers.
 Different Structural formula means, Different bond pattern or Different
arrangement of σ bonds or Different connectivity of atoms.
 The key to organic chemistry is crystal clear understanding
of different terms used.

3. ISOMERS
Examples
1-chloropropane and 2-chloropropane has different structural fumular

4.  Example 2
 cis-2-butene and trans-2-butene has same structural
formula

5. Types of structural isomers
. Chain Isomerism
2. Positional Isomerism
3. Functional Isomerism
4. Metamerism.
5. Tautomerism
Chain Isomerism
: Isomers which have same functional groups but different
arrangement of carbon skeleton in principal chain or side chains
are chain isomers.
Note 1. No of atoms same

6. .Ethylbenzene and o-Xylene. 2. Butanoicacid and 2-methylpropanoicacid

7. Positional Isomerism: Isomers which have same functional groups ,same arrangement of
carbon skeleton but different position of functional groups or substituents
Example 1. 1-butanol & 2-butanol 2. O-Xylene & m-
Xylene

8. Functional Isomers: Isomers which have different functional
group
Example 1. 1-butanol & Ethoxyethane 2. Ethanal and
Oxirane

9.  Metamers: Isomers which have different carbon chain
length along a functional group with hetro atom (Ex- Ethers,
Esters, secondary amines, tertiary amines , Secondary
amides
 Example 1. Methoxypropane & Ethoxyethane 2. Ethylethanoate and
Methylpropanoate

10.  Tautomers: A type of functional Isomers which exist in rapid
equilibrium in solution are called functional isomers.
Tautomers are interconvertable in solution
 Tautomers usually differs in position of H atom at α carbon.
Interconversion of tautomers can be catalysed.
 Tautomers can’t be seperated in solution at normal
temperature.
 The more stable form dominates in equillibrium.
15 15Isomers Isomers
 Only the stable tautomeric form is counted while counting
isomers.
Type-1 Keto- Enol tautomerism.
 Example Cyclohexanone and cyclohexenol
 ◆ Type-1 Nitro-Acinitro ◆ Example nitrocyclohexane and
acinitrocyclohexen

11.  Type-4 Cyano - isocyano ◆ Example Cyanicacid and
isocyanicacid