Constitutional isomers: Positional,functional and chain isomerism

Constitutional isomers are further divided into three types.They are:
1)Positional isomers
2)Functional group isomers
3)Chain isomers

Positional isomers:

The compounds having the same molecular formula but differ in the position of double bond or triple bond or the functiobla group are called positional isomers.
Ex:  But-1-ene ; But-2-ene.
      Pentan-1-ol ; Pentan-2-ol.

Functional group isomers:

The compounds having the same molecular formula but which differ in the functional groups is called functional group isomers.
Ex:C₂H₆O⇒CH₃-CH₂-OH(Ethanol)  ;  CH₃-O-CH₃(Dimethyl ether).

Chain isomers:

The compounds having same molecular formula but differ only in arrangements of carbon atom in the main carbon chain.
Ex: C₄H₁₀⇒Butane ; 2-Methyl propane.

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