Difference Between Ethene and Ethyne

Main Difference – Ethene vs Ethyne

Ethene and Ethyne are organic compounds found under the category of hydrocarbons. These are called hydrocarbons because these compounds are composed of entirely C and H atoms. Hydrocarbons can be either aliphatic or aromatic. Aliphatic hydrocarbons are linear or branched structures whereas aromatic hydrocarbons are cyclic structures. Both Ethene and Ethyne are aliphatic hydrocarbons. Ethene is an alkene and is composed of two carbon atoms and four hydrogen atoms. Ethyne is an alkyne and is composed of two carbon atoms and two hydrogen atoms. Ethene is the IUPAC name for Ethylene. Ethyne is the IUPAC name for Acetylene. The main difference between Ethene and Ethyne is that Ethene is composed of sp² hybridized carbon atoms whereas Ethyne is composed of sp hybridized carbon atoms.

Key Areas Covered

1. What is Ethene
      – Definition, Properties, Reactions, Applications
2. What is Ethyne
      – Definition, Properties, Reactions, Applications
3. What are the Similarities Between Ethene and Ethyne
      – Outline of Common Features
4. What is the Difference Between Ethene and Ethyne
      – Comparison of Key Differences

Key Terms: Acetylene, Aliphatic Hydrocarbon, Alkene, Alkyne, Aromatic Hydrocarbon, Ethene, Ethylene, Ethyne, Hydrocarbons

What is Ethene

Ethene is an alkene. The common name for ethene is ethylene. It is composed of two carbon atoms and four hydrogen atoms. The chemical formula of ethene is C₂H₄. The two carbon atoms are bonded to each other through a double bond. Hydrogen atoms are bonded to these carbon atoms through single bonds. Since carbon atoms can make a maximum of 4 covalent bonds, two hydrogen atoms are bonded to each carbon atom. The bond angle between these bonds is about 121.3^o.

Figure 1: Molecular Structure of Ethene

Ethene is planar. The two carbon atoms are sp² hybridized in order to form three sigma bonds. Therefore, there is one p orbital per carbon atom that remains un-hybridized and these p orbitals form the pi bond of the double bond. The presence of this pi bond causes the reactivity of ethene.

The natural sources of ethene include natural gases and petroleum oil. The molar mass of ethene is about 28 g/mol. At standard temperature and pressure, ethene is a colorless gas. It is a flammable gas having a characteristic odor. The melting point of ethene is about -169.4^oC. The boiling point is about -103.9^oC.

Ethene is used in polymerization processes as a monomer to produce polyethylene. It is also used to produce ethylene oxide in order to produce detergents, surfactants like chemicals.

What is Ethyne

The common name for ethyne is acetylene. Ethyne is an alkyne composed of two carbon atoms and two hydrogen atoms. The two carbon atoms are bonded to each other through a triple bond. In other words, there is a sigma bond and two pi bonds between the two carbon atoms. The two hydrogen atoms are bonded to each carbon atom through single bonds. The carbon atoms of ethyne are sp hybridized. Therefore, there are two un-hybridized p orbitals in each carbon atom. These p orbitals together form the two pi bonds. The molecular shape of ethyne is linear. Therefore, the bond angle between atoms is 180^oC.

Figure 2: Molecular Structure of Ethyne

The chemical formula of ethyne is C₂H₂. The molar mass of ethyne is about 26.04 g/mol. It is a colorless and odorless gas at room temperature and pressure. The melting point is -80.8^oC. The triple point of ethyne is equal to the melting point. Therefore, at temperatures below the triple point, solid acetylene can be directly converted into gaseous ethyne (this is called sublimation). The sublimation point of ethyne is -84.0^oC.

Ethyne is commonly used to produce the oxy-acetylene flame for welding purposes. It is also used as the starting material for the production of like chemical compounds ethanol, ethanoic acid, and PVC.

Similarities Between Ethene and Ethyne

Both molecules are composed of two carbon atoms.
Both molecules have sigma bonds and pi bonds.
The carbon atoms of both molecules have un-hybridized p orbitals.
Both molecules exist in the gaseous phase at room temperature and atmospheric pressure.
Both are hydrocarbons.

Definition

Ethene: Ethene is a hydrocarbon composed of two carbon atoms and four hydrogen atoms.

Ethyne: Ethyne is a hydrocarbon composed of two carbon atoms and two hydrogen atoms.

Common Name

Ethene: The common name used for ethene is ethylene.

Ethyne: The common name used for ethyne is acetylene.

Hybridization of Carbon

Ethene: The carbon atoms are sp² hybridized in ethene.

Ethyne: The carbon atoms are sp hybridized in ethyne.

Molecular Formula

Ethene: Ethene is given as C₂H₄.

Ethyne: Ethyne is given as C₂H₂.

Distance Between Two Carbon Atoms

Ethene: Distance between two carbon atoms in ethene is about 133.9 pm.

Ethyne: Distance between two carbon atoms in ethyne is about 120.3 pm.

Distance Between Carbon Atom and Hydrogen Atom

Ethene: The distance between C and H in ethene is about 108.7 pm.

Ethyne: The distance between C and H in ethyne is about 106.0 pm.

Molecular Geometry

Ethene: The geometry of ethene is planar.

Ethyne: The geometry of ethyne is linear.

Number of Pi Bonds

Ethene: There is one pi bond in ethene.

Ethyne: There are two pi bonds in ethyne.

Molar Mass

Ethene: The molar mass of ethene is about 28 g/mol.

Ethyne: The molar mass of ethyne is about 26.04 g/mol.

Melting Point

Ethene: The melting point of ethene is -169.4oC.

Ethyne: The melting point of ethyne is –80.8^oC.

Bond Angle

Ethene: The bond angle in ethene is 121.3^o.

Ethyne: The bond angle in ethyne is 180^o.

Conclusion

Ethene and Ethyne are important hydrocarbon compounds used for industrial purposes. These molecules are often used as monomers for the production of polymers through polymerization processes. The main difference between Ethene and Ethyne is that Ethene is composed of sp² hybridized carbon atoms whereas Ethyne is composed of sp hybridized carbon atoms.

References:

1. “Ethylene (H2C=CH2).” Encyclopædia Britannica. Encyclopædia Britannica, inc., n.d. Web. Available here. 03 Aug. 2017.
2. “Acetylene.” Wikipedia. Wikimedia Foundation, 30 July 2017. Web. Available here. 03 Aug. 2017.

Image Courtesy:

1. “Ethene structural” By McMonster – Own work (Public Domain) via Commons Wikimedia
2. “Ethyne-2D-flat” (Public Domain) via Commons Wikimedia