Isomers of Butane: Types & Structural Isomers

Isomers of Butane are of two types, namely isobutane (2-methylpropane) and n-butane. In Chemistry, isomers are those compounds that have different chemical structures and the same molecular formula.

•  Isomers have different chemical and physical properties. This is because of their distinct structures. 
• Butane is considered an alkane. 
• The chemical formula of Butane is C₄H₁₀. 
• It consists of 4 carbon atoms and 10 Hydrogen atoms together. 
• The structure of butane is in the form of a long straight chain. 

Read More: Organic Compounds

Key Terms: Isomers, Atoms, Butane, Alkane, Ethane, Methane, Chain Isomerism, stereoisomerism

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What are Isomers? 

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'Isomers' is derived from the Greek words i.e. 'Isos' and 'meros'. It means 'equal parts'. The word “isomer” is derived from the Greek words “isos” and “meros”, which mean “equal parts”.

• Isomers are chemical compounds which share the same chemical formula but vary in their chemical structures. 
• Isomers have various chemical properties. So, it can be said that isomers are those compounds which exhibit the phenomenon of isomerism. 
• In this phenomenon of isomerism, the structure varies due to the arrangements of atoms in the molecule. 

Also Read: 

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Types of Isomers

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On the basis of the structure of atoms, it is classified into various types. The chemical compounds like methane, butane, ethane, etc are structured in different ways. 

Structural Isomerism

In this type of isomerism, the compounds are distributed in different directions and make varying structure. For example, Isobutane and n-butane. 

Chain Isomerism

In this type of Isomerism, the compounds have different branches of Carbon atoms but the molecular formula is the same for it. For example - 2 methyl butane (Isopentane) 

Isopentane

Functional Isomerism

In this type of Isomerism, the compounds have the same molecular formula but vary in their functional group. For example - Ethanol. Ethanol contains 'OH' as its functional group and the molecular formula is C₂H₆O. 

Ethanol

Stereoisomerism

In this type of isomerism , the compounds have molecular formulas with different spatial orders of atoms. This is known as stereoisomerism. For example: 1,2 - dichloroethene. The chemical formula is (C₂H₂Cl₂). There are two types of stereoisomerism namely Optical isomerism and Geometric isomerism. 

1,2 - dichloroethene

Constitutional Iomers of Butane

In this type of isomerism, the chemical compounds have the same molecular formula with different structural formula. 

• The atoms in molecules are connected in a different form.
• In order to determine the constituency of the atoms, the number of each atom is counted in both molecules. 

This can be understood with an example.

• In Isobutane, the carbon atoms are arranged with a side chain because the molecules have different connectivity of atoms. 
• Whereas in case of N-butane, the connectivity of carbon atoms differ. They are arranged in the form of a straight chain. 
• But both these isomers have same molecular formula i.e. C₄H₁₀. 

Conformational Isomers of Butane

This type of conformational isomerism can be seen in alkanes. This is because of the presence of C-C bonds. This can be understood with an example based on the rotation around the sigma bond. 

• The stereoisomers change their form by rotation. 
• When the molecules of butane are rotated at the axis of Carbon bond, then the Conformational Isomers of butane is obtained. 
• In this type of isomerism, the identical groups are seen that makes the bond unstable. 
• The rotation leads to the spatial arrangements of the hydrogen atoms with Carbon.
• This is known as conformational isomers of butane.
• Example: Butane, there are three conformers attached with the two methyl (CH₃) groups. 

Conformational Isomers of Butane

Staggered Conformation of Butane

A conformer which has a dihedral angle of 60 degrees, wherein the H-atoms of C-1 are close enough to the H-atoms of C-2 are known as staggered conformation. 

• The staggered conformer is known to be more stable than the eclipsed conformer. 
• This is due to the H-atoms which are separated by an adequate distance. 
• Butane staggered conformers are of two types: anti and gauche conformers. 
• When one carbon atom in butane is fixed, while spinning the other, three types of conformers can be obtained: eclipsed, anti, and gauche.
• In anti-form, both methyl groups of butane can be found at anti position. It is considered to be one of the most stable butane forms. The other type is known as gauche or skew conformation.

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Isomers of Butane

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Isomers are composed of more than two molecules. That's why their structure as well as their properties are different. The isomers of Butane are: Isobutane (2-methylpropane) and n-butane.

Thus, some of the Properties of Isomers of Butane are:

• Those isomers who form branched- chain have low melting and boiling points. Its example is isobutane. 
• The melting point of isobutane is -160° C and boiling point is -12° C
• The properties of N - butane are different. The boiling point is 0 °C and melting point is -138 °C. The lower the boiling and melting points.Thus,it shows if there is low melting and boiling point of the compound, the more branched chain can be formed. 
• Butane is highly inflammable in nature. So, it can be used for heating purposes easily. 

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Structural Isomers of Butane

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Butane is a chemical compound which consists of 4 carbon alkane and 10 atoms of hydrogen. 

• The chemical formula of Butane is C₄H₁₀. It constitutes two different types of structures.
•  It simply means, the structures are straight as well as branched chain forms. 
• The main aim of the structure is to complete the valency of the carbon atom in order to form the four bonds. 

Butane consists of two structural/constitutional isomers. They are N-butane and Isobutane. According to the IUPAC name, they are known as butane and 2 - methylpropane. 

The structure of N-butane is present in the form of a straight chain because of the arrangement of all Carbon atoms. Whereas isobutane has the side chain. 

Structural Isomers of Butane

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Things to Remember

• Alkanes are chemical compounds that exhibit the phenomenon of isomerism. 

Example - Methane (CH₄), ethane (C₂H₆), propane (C₃H₈) and butane (C₄H₁₀). 

• Isomers are those compounds that have the same molecular formula but their chemical structure is different. 
• Butane is an example of alkane and the chemical formula of Butane is C₄H₁₀.
• There are two isomers of Butane and they are known as N-butane and Isobutane. Their structures are formed in a ring chain and in a straight chain. 
• There are two types of isomerism. They are known as structural or constitutional isomerism and stereoisomerism/spatial isomerism. 

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Previous Year Questions

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