Difference Between Methane and Ethane

Main Difference – Methane vs Ethane

Methane and ethane are simple organic molecules. These are alkane compounds. Both methane and ethane are colorless and odorless gaseous compounds at room temperature. Methane is a major greenhouse gas. Although ethane is also a greenhouse gas, it is less abundant in the atmosphere. There are many differences between chemical and physical properties of methane and ethane. The main difference between methane and ethane is that methane contains only one carbon atom bonded to four hydrogen atoms whereas ethane contains two carbon atoms bonded to each other and each carbon atom is bonded to three hydrogen atoms.

Key Areas Covered

1. What is Methane
      – Definition, Chemical and Physical Properties
2. What is Ethane
      – Definition, Chemical and Physical Properties
3. What are the Similarities Between Methane and Ethane
      – Outline of Common Features
4. What is the Difference Between Methane and Ethane
      – Comparison of Key Differences

Key Terms: Alkane, Combustion, Ethane, Flammable, Greenhouse Gas, Hydrocarbons, Methane, Natural Gas

What is Methane

Methane is a colorless and odorless gas having the chemical formula CH₄. It is the smallest alkane having only one carbon atom bonded to four hydrogen atoms. The molar mass of methane is about 16 g/mol. The boiling point of methane is about 161^oC. Due to the small size, the methane vapor is lighter than normal air.

Figure 1: Molecular Structure of Methane

The geometry of the molecule is tetrahedral. This gas is a flammable gas. It ignites easily, producing heat and flame. The major source of methane is natural gas. About 70% of natural gas is methane. Apart from methane, natural gas is composed of ethane, propane and some other hydrocarbons in trace amounts. However, methane is also produced as biogas via anaerobic bacterial decomposition of plant matter.

Methane readily undergoes combustion. It is a highly exothermic reaction. The end products given by the methane combustion are carbon dioxide and water vapor. The incomplete combustion of methane forms carbon soot (carbon dust). Methane is used to produce some important chemicals such as methanol, chloroform, etc.

Methane is considered as a greenhouse gas because it can absorb sun’s heat, warming the atmosphere. This is done by absorbing infrared radiation and radiating the heat back to the earth’s surface. This results in changes in climate.

What is Ethane

Ethane is a colorless and odorless gas having the chemical formula C₂H₆. The molar mass of ethane is about 30 g/mol. It is a hydrocarbon compound and is an alkane. The ethane molecule is composed of two carbon atoms bonded to each other via a single covalent bond. Each carbon atom is bonded to three hydrogen atoms.

The geometry of ethane is given considering one carbon atom; it is tetrahedral at one carbon atom. Since there is a C-C sigma bond, the other sigma bonds are free to rotate around this C-C bond. Therefore, ethane has conformational isomers. It has eclipsed conformation and staggered conformation.

Figure 2: The Isomers of Ethane. Eclipsed Conformation (Left) and Staggered Conformation (Right)

Combustion of ethane is highly exothermic and produces a high amount of heat. The complete combustion of ethane produces carbon dioxide and water vapor as end products. The incomplete combustion of ethane produces carbon monoxide along with carbon dioxide and water vapor. Sometimes carbon soot (carbon black) is also produced.

Ethane can be found in natural gas. About 15% of natural gas is ethane. The boiling point of ethane is about −88.5 °C. Therefore, ethane is a gaseous compound at room temperature. Ethane is also a greenhouse gas. But since it is less abundant in the atmosphere, there is no considerable effect of ethane for the greenhouse effect.

Similarities Between Methane and Ethane

Both are hydrocarbon compounds. Both are alkanes.
These are gaseous compounds at room temperature.
Both are flammable gases.
Both are saturated compounds (no double or triple bonds present).

Definition

Methane: Methane is a colorless and odorless gas having the chemical formula CH₄.

Ethane: Ethane is a colorless and odorless gas having the chemical formula C₂H₆.

Number of Carbon Atoms

Methane: Methane has only one carbon atom per molecule.

Ethane: Ethane has two carbon atoms per molecule.

C-C Bond

Methane: There are no C-C bonds in methane.

Ethane: Ethane has one C-C bond.

Conformational Isomers

Methane: There are no conformational isomers for methane.

Ethane: Ethane has eclipsed isomers and staggered isomers as conformational isomers.

Boiling Point

Methane: The boiling point of methane is about -161ºC.

Ethane: The boiling point of ethane is about −88.5 ºC.

Occurrence

Methane: Methane is the principal component of natural gas; about 70%.

Ethane: Natural gas has about 15% of ethane.

Greenhouse Effect

Methane: Methane highly contributes to the greenhouse effect.

Ethane: Ethane has a less contribution to greenhouse effect because ethane vapor is less abundant in the atmosphere.

Conclusion

Methane and ethane both are hydrocarbon compounds that can be found in natural gas. These are flammable gases. The main difference between methane and ethane is that methane contains only one carbon atom bonded to four hydrogen atoms whereas ethane contains two carbon atoms bonded to each other and each carbon atom is bonded to three hydrogen atoms.

References:

1. Libretexts. “1.9: Ethane, Ethylene, and Acetylene.” Chemistry LibreTexts, Libretexts, 21 July 2016, Available here.
2. The Editors of Encyclopædia Britannica. “Methane.” Encyclopædia Britannica, Encyclopædia Britannica, inc., 24 Mar. 2017, Available here.
3. “Methane.” National Center for Biotechnology Information. PubChem Compound Database, U.S. National Library of Medicine, Available here.

Image Courtesy:

1. “Methane-2D-small” (Public Domain) via Commons Wikimedia
2. “Newman projection ethane” By Aglarech at de.wikipedia; Leyo – Own work (Public Domain) via Commons Wikimedia