Difference Between Acetylene and Ethylene

Key Difference – Acetylene vs Ethylene
 

The key difference between acetylene and ethylene is that acetylene has a triple bond between two carbon atoms whereas ethylene has a double bond between two carbon atoms.

The names acetylene and ethylene sound similar, but they are different hydrocarbon compounds. However, they also have some similarities. This article describes both the similarities and differences between acetylene and ethylene.

CONTENTS

1. Overview and Key Difference
2. What is Acetylene
3. What is Ethylene
4. Similarities Between Acetylene and Ethylene
5. Side by Side Comparison – Acetylene vs Ethylene in Tabular Form
6. Summary

What is Acetylene?

Acetylene is an organic compound having the chemical formula C₂H₂. Furthermore, it is the simplest alkyne among hydrocarbons. An alkyne is a compound having a triple bond between two carbon atoms. Therefore, acetylene has a triple bond between the two carbon atoms it has. There are two pi bonds and one sigma bond between those carbon atoms. The molecule has a linear geometry because one carbon atom can form only four covalent bonds (acetylene has a triple bond and a single bond, C-H, which makes the molecule linear). Therefore, the carbon atoms of the acetylene molecule are sp hybridized.

Chemical Properties of Acetylene

Some chemical facts about acetylene are as follows:

• Chemical formula = C₂H₂
• Molar mass = 26.04 g/mol
• Physical state at room temperature = it is a colorless gas
• Odor = odorless
• Melting point = -80.8°C
• Boiling point = -84°C
• Solubility in water = slightly soluble
• IUPAC name = Ethyne

Moreover, acetylene does not exist as a liquid in atmospheric pressure. Thus, it has no actual melting point. The melting temperature given above is actually the triple point of acetylene. Therefore, the solid form of acetylene undergo sublimation rather than melting. There, solid acetylene is converted into vapor.

Figure 01: Use of oxy-acetylene Flame

The major application of acetylene is in welding processes. The oxy-acetylene flame is a high-temperature flame that is important in welding and cutting. We can produce this flame from the combustion of acetylene with oxygen.

What is Ethylene?

Ethylene is an organic compound having the chemical formula C₂H₄. There are two carbon atoms bonded to each other via a double bond (a pi bond and sigma bond). Therefore the ethylene molecule has two sp2 hybridized carbon atoms. Since a carbon atom is able to form four chemical bonds, there are two hydrogen atoms bonded to each carbon atom via single bonds. Then the ethylene molecule has a planar structure.

Figure 02: The Chemical Structure of Ethylene

Some chemical facts about ethylene are as follows:

• Chemical formula = C₂H₄
• Molar mass = 28.05 g/mol
• Physical state at room temperature = it is a colorless, flammable gas
• Odor = sweet odor
• Melting point = −169.2°C
• Boiling point = −103.7°C
• Solubility in water = slightly soluble
• IUPAC name = Ethene

The major source of ethylene is crude oil and natural gases. There are three main processes used to produce ethylene from these sources. They are;

1. Steam cracking of ethane and propane
2. Steam cracking of naphtha
3. Catalytic cracking of gas oil

Ethylene possesses important uses as monomers for the production of polymers such as polyethylene via addition polymerization. Polyethylene is a common packaging material. Furthermore, in biological systems, ethylene is important as a plant hormone since it stimulates the fruit ripening process.

What are the Similarities Between Acetylene and Ethylene?

• Both are small hydrocarbons.
• Acetylene and Ethylene are composed only of carbon atoms and hydrogen atoms.
• Both are colorless gases.
• Both Acetylene and Ethylene are flammable gases.
• Acetylene and Ethylene are planar structures.

What is the Difference Between Acetylene and Ethylene?

Summary – Acetylene vs Ethylene

Acetylene and ethylene are very important hydrocarbon compounds because of their wide range of applications. The difference between acetylene and ethylene is that acetylene has a triple bond between two carbon atoms whereas ethylene has a double bond between two carbon atoms.

Reference:

1. “Acetylene.” Wikipedia, Wikimedia Foundation, 14 Apr. 2018. Available here  
2. “Ethylene.” Wikipedia, Wikimedia Foundation, 18 Apr. 2018. Available here
3. “Acetylene.” National Center for Biotechnology Information. PubChem Compound Database, U.S. National Library of Medicine. Available here 

Image Courtesy:

1.’US Navy 070413-N-2943C-001 Hull Technician Fireman Troy Heffner lights up an oxygen acetyl torch prior to a welding job in the hull technician shop’By U.S. Navy photo by Mass Communication Specialist Carlos Cepeda (Public Domain) via Commons Wikimedia  
2.’Ethylene-3D-balls’By Benjah-bmm27 – Own work, (Public Domain) via Commons Wikimedia  

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