Draw the product of the complete hydrogenation of ethyne.
The Correct Answer and Explanation is:
The complete hydrogenation of ethyne (C₂H₂) produces ethane (C₂H₆).
Structural Formula of Ethane (Product):
H – C – C – H
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H H
Alternatively written as:
CH₃ – CH₃
Explanation:
Ethyne, also known as acetylene, is the simplest alkyne with the formula C₂H₂. Its structure consists of two carbon atoms connected by a triple bond, with each carbon bonded to one hydrogen atom. The triple bond includes one sigma bond and two pi bonds, making ethyne a highly unsaturated molecule.
Hydrogenation is the process where hydrogen molecules (H₂) are added to an unsaturated compound in the presence of a catalyst. In complete hydrogenation, all multiple bonds (double or triple) are converted into single bonds. Catalysts such as nickel, palladium, or platinum are typically used to facilitate the reaction under heat and pressure.
In the case of ethyne, the complete hydrogenation involves the addition of two moles of hydrogen gas. The reaction proceeds as follows:
C₂H₂ + 2H₂ → C₂H₆
During this reaction:
- The triple bond between the carbon atoms breaks.
- Two new hydrogen atoms add to each carbon.
- The final product, ethane (C₂H₆), is formed.
Ethane is a saturated hydrocarbon belonging to the alkane family. All carbon-carbon and carbon-hydrogen bonds in ethane are single covalent bonds, making it chemically stable and less reactive compared to ethyne.
This transformation is significant in the petrochemical industry, where unsaturated hydrocarbons are hydrogenated to produce alkanes used as fuels or starting materials for other chemical processes.
Thus, the complete hydrogenation of ethyne converts an unsaturated, reactive molecule into a stable, saturated alkane, specifically ethane.
