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What is an isomer? Write the isomers of butane with structural formula

An isomer is a chemical compound having the same number and types of atoms as another chemical compound but differ in arrangement of atoms. When the same number and type of atoms can assume different configurations and orientation, the phenomenon is called isomerism.

Types of isomers:

1.  Structural Isomers: Structural isomers, also known as constitutional isomers, are where two or more organic compounds have the same molecular formulas but different structures. They can be further divided into three main subgroups: chain isomers, position isomers, and functional group isomers depending upon where the difference occurs in their structure.

2. Stereoisomers: Stereoisomers are isomers that differ in spatial arrangement of atoms, rather than order of atomic connectivity. They can be further divided into Geometric Isomers and Optical isomers.

Geometric isomers exhibit changes in orientation of atoms around a chemical bond e.g. Cis and Trans isomers. Optical isomers are two organic compounds that are non-superimposable mirror images of each other. They are also known as enantiomers.


Butane is an organic compound from the Hydrocarbon Series called Alkanes. The molecular formula for Butane is C4H10. It consists of 4 Carbon Atoms joined with 10 Hydrogen atoms via Single bonds. The Prefix “But-“ is derived from 4 carbon butyric acid and the suffix “-ane” comes from its functional group series i.e Alkanes.

Butane exists in two different forms of structural isomers called normal butane, or unbranched butane, and isobutane, or i-butane. The number and types of atoms in both of them remain the same, but only differ in their structure. Normal Butane is a long chain alkane whereas isobutane has a branched structure in which a Methyl group (-CH3) is bonded to the second carbon atom. Their structural formulas are given below:
According to IUPAC nomenclature, these isomers are called simply butane and 2-methylpropane.

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