How can you synthesize acetylene from ethane?
What are the reagents used and products formed along the way.
The Correct Answer and Explanation is :
Acetylene (C₂H₂) can be synthesized from ethane (C₂H₆) through a process called dehydrohalogenation, which involves the removal of hydrogen halides (such as HCl) from the ethane molecule. This transformation is typically achieved by a reaction known as pyrolysis or cracking. Here’s a step-by-step breakdown:
Reagents and Process:
- Reagents:
- Ethane (C₂H₆): The starting material.
- Oxygen (O₂) or Chlorine (Cl₂): These can be used in specific reactions to induce the necessary dehydrogenation steps.
- High Temperature: Pyrolysis reactions are carried out at very high temperatures (around 800–1000°C) to break the carbon-carbon and carbon-hydrogen bonds.
- Steps:
- Step 1: Pyrolysis or Cracking: Ethane is heated to high temperatures (approximately 800–1000°C) in the presence of limited oxygen or under conditions of low oxygen. This process breaks the ethane molecules into smaller fragments, typically producing ethylene (C₂H₄) as one of the major products.
- Step 2: Dehydrogenation of Ethylene: Ethylene can then undergo dehydrogenation, where hydrogen atoms are removed from the molecule. This step produces acetylene (C₂H₂) as the desired product. This can be achieved using a catalyst like copper or in the presence of heat and a small amount of oxygen.
- Reactions:
- Ethane to Ethylene:
[
C_2H_6 \rightarrow C_2H_4 + H_2
] - Ethylene to Acetylene:
[
C_2H_4 \rightarrow C_2H_2 + H_2
]
Products Formed:
- Acetylene (C₂H₂): This is the final desired product.
- Ethylene (C₂H₄): An intermediate product.
- Hydrogen (H₂): Released as a byproduct in both stages of the reaction.
Explanation:
The conversion of ethane to acetylene involves two major steps: first, the cracking of ethane to ethylene (C₂H₄), followed by the dehydrogenation of ethylene to acetylene (C₂H₂). This is a well-known industrial process because acetylene is a valuable compound in various chemical syntheses, including the production of acetylene black and other chemicals. The process requires precise control of temperature and oxygen levels to avoid unwanted side reactions.