Isomerism
(Short Note)
Definition
The phenomenon in which different
compounds have the same molecular formula but different structural formula or
electronic configuration is known as Isomerism.
The different compounds are called
Isomers.
Types of Isomerism
There are various types of isomerism,
but the four important types are
1. Chain Isomerism
2. Position Isomerism
3. Functional group Isomerism
4. Metamerism
1 Chain Isomerism
The phenomenon in which different
compounds have the same molecular formula but differ in length of carbon chain
is called Chain Isomerism. The structures are known as Chain Isomers.
Examples
1. Methane, Ethane and Propane have
no chain isomers because the cannot be rearranged with small carbon chain.
CH4 CH3-CH3 CH3-CH2-CH3
2. The carbon chain of butane (C4H10)
is long enough. So, butane has two isomers.
CH3-CH2-CH2-CH3 (n-butane)
CH3-CHCH3-CH3 (iso-butane)
3. Pentane (C5H12) shows the
following isomers.
CH3-CH2-CH2-CH2-CH3 (N-PENTANE)
CH3-CHCH3-CH2-CH3 (ISO-PENTANE)
In saturated hydrocarbons, the number
of isomers increases with increase in number of carbon atoms. This is the
reason why decane shows 75 isomers.
2. Position Isomerism
The phenomenon in which different
compounds have same molecular formula but differ in position of functional
group, double bond or triple bond in same length of carbon chain is called
Position Isomerism. The structures are called Position Isomers.
Examples
1. Propyl alcohol shows two position
isomers.
Diagram Coming Soon
2. Butene C4H8 has two position
isomers.
Diagram Coming Soon
3. Functional Group Isomerism
The phenomenon in which different
compounds have same molecular formula but differ in functional groups is called
functional group Isomerism. The structures are known as functional group
isomers.
4. Metamerism
The phenomenon in which different
compounds have same molecular formula and functional group but different alkyl
groups attached to the same multivalent atom is called metamerism.
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