Isomers of Butane

Isomerism is the phenomenon in which molecules with the same number and type of atoms have the same chemical formula but differ in their physical and chemical properties and structures. Let us look at the isomers of butane, their properties and their real-life applications in the article below.

What are Isomers?

Isomers are compounds that have the same molecular formula but differ in chemical structures. Isomers are chemical compounds that have the same chemical formula but differ in their properties and atom arrangement in the molecule. Because of their distinct structures, isomers can have diverse physical and chemical properties.

How many Isomers does Butane have?

Butane is a four-carbon alkane, hence its chemical formula is C4H10. Butane has two structural (also known as constitutional) isomers: normal butane, also known as unbranched butane, and isobutane, commonly known as i-butane. These isomers are known as butane and 2-methylpropane in IUPAC nomenclature.

Constitutional Isomers of Butane (Based on connectivity)

Structural isomerism is another name for constitutional isomerism. Constitutional isomers are isomers that have the same chemical formula but differ in how their atoms or groups of atoms are connected. In other words, constitutional isomers have varying atom connections in molecules. To determine whether two molecules are constitutional isomers, we must count the number of atoms in both molecules.

Butane is available in both straight and branched chain forms. Both of these butane structures satisfy the valency of the carbon atom and hence form four bonds. There are 13 covalent bonds in both butane and isobutane.

Isobutane got its name because it is a constitutional isomer of butane. The carbon atom coupled to hydrogen and two -CH3 groups is the structural unit of the ‘iso’ group. This is also referred to as chain isomerism. These are the isomers with different carbon skeletons.

In the case of n-butane, all carbon atoms are in a straight chain, whereas in the case of isobutane, the molecule contains a side chain. As a result, they have different atom connections and are constitutional isomers of each other.

Isomers of Butane

Conformational Isomers of Butane (Based on rotation around sigma bond)

Because of free rotation around sigma bonds, different spatial configurations of atoms in molecules can be obtained. All of these configurations are referred to as conformations. Because of the presence of C-C bonds, alkanes typically exhibit conformational isomerism. Because the carbon-carbon link in butane is a sigma bond, rotation around the single carbon-carbon bond is feasible. This rotation around the C-C single bond is possible without affecting orbital overlap.

For example, when we rotate a butane molecule along its C-C bond axis, we get eclipsed, gauche, and anti-butane structural isomers. Because the eclipsed conformation has identical groups squarely in line with one another, it is unstable. The existence of identical groups at 60 degrees from one another is referred to as gauche conformation. Gauche is more stable than eclipse confirmation because there is a less steric barrier between the same molecules.

Staggered Conformation of Butane

The study of conformers is primarily concerned with the arrangement of atoms or groups in relation to a central atom. A conformer with a dihedral angle of 60 degrees, the H-atoms of C-1 are close enough to the H-atoms of C-2. This is known as staggered conformation. The staggered conformer is more stable than the eclipsed conformer because the H-atoms are separated by a sufficient distance. Butane staggered conformers come in two varieties: anti and gauche conformers. When we fix one carbon atom in butane and spin the other, we get three types of conformers: eclipsed, anti, and gauche.

Staggered Conformation

Structural Isomers of Butane

Structural Isomers of Butane

Properties of Isomers of Butane

Because isomers are separate molecules, their properties differ. Branched-chain isomers typically have lower boiling and melting points than straight-chain isomers. Iso-butane, for example, has boiling and melting temperatures of -12 °C and -160 °C, respectively, whereas n-butane has 0 °C and -138 °C. The lower the boiling and melting points, the more branching there is. Natural gas liquids and refinery gas streams can be used to produce isomers of butane.

Frequently Asked Questions

Q1. What Does the Term Isomerism Mean?

Answer. Isomerism is defined as the phenomena in which organic compounds with similar chemical formulas but different structural atom arrangements exist. That is, they have different structural formulas. Organic substances are classified as isomers. The isomers of butane compounds are isobutane and n-butane.

Q2. What is the most common application for butane?

Answer. Butane is a highly flammable gas, which makes it suitable for heating. It’s frequently marketed in bottles for use in camping stoves or outdoor grills. When it was discovered that the substance, chlorofluorocarbons (CFCs), destroyed the ozone layer, butane was utilized as a substitute ingredient to act as a propellant in the aerosol spray cans.

Q3. What are the main types of isomerism?

Answer. The two primary types of isomerism are structural or constitutional isomerism, which occurs when the bonds between the atoms differ, and stereoisomerism or spatial isomerism, which occurs when the bonds are the same but the relative positions of the atoms differ.

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