Table of Contents

What is Ethyne?

Ethyne, also known as acetylene, is an organic chemical compound with the chemical formula C2H2. Since the entire chemical composition only features hydrogen and carbon atoms, this compound is a hydrocarbon. Ethyne is regarded by many to be the simplest alkyne since it consists of only two carbon atoms, which are triply bonded to each other. Pure ethyne is known to be highly unstable. Therefore, it is not uncommon for ethyne to be handled in a solution. Ethyne (or acetylene) is an unsaturated hydrocarbon since it contains a carbon-carbon triple bond.

How is Ethyne prepared?

Ethyne can be prepared by subjecting methane to partial combustion. This compound can also be prepared from the hydrolysis of calcium carbide (a chemical compound with the formula CaC2, also known as calcium acetylide). The chemical equation for this reaction between calcium carbide and water is provided below.

H2O + CaC2 → C2H2 + Ca(OH)2

Thus, the hydrolysis of calcium carbide produces calcium hydroxide and ethyne as the final products.

Structure of Ethyne Molecules

The ethyne molecule features a triple bond between two carbon atoms, each of which is singly bonded to one other hydrogen atom. It can be noted that all four atoms align in a straight line with bond angles of approximately 180o. It can also be noted that the bond length of the carbon-hydrogen bond in the ethyne molecule is roughly equal to 106 picometres whereas the carbon-carbon bond length in the molecule is approximately equal to 120.3 picometres. The structure of the ethyne molecule is illustrated below.

Structure of Ethyne Molecules

Properties of Ethyne

The notable physical and chemical properties of ethyne are listed below.

  • The molar mass of ethyne is equal to 26.038 grams per mole.
  • Under standard conditions for temperature and pressure (usually abbreviated to STP), ethyne is known to exist as a colourless gas which does not have any distinct odour.
  • The density of this compound is known to be approximately equal to 1.097 grams per litre.
  • The melting point of ethyne is roughly equal to -80.8 degrees Celsius (or 192.3 Kelvin).
  • Ethyne is known to be slightly soluble in water.
  • The molecular shape of the ethyne molecule is linear.

What are the uses of Ethyne?

Since ethyne burns with a very hot flame, one of its most notable applications is in oxyacetylene gas welding and oxyacetylene gas cutting. When ethyne is subjected to combustion with oxygen, the flame created is known to have a temperature of roughly 3600 Kelvin. The energy released for every gram of fuel subjected to combustion corresponds to 11.8 kilojoules per gram.

Another vital application of ethyne is in the production of portable lighting. For use in mining activities, calcium carbide is often employed in combination with water to generate acetylene, which is used in lamps. However, it is important to note that such lighting devices have been rendered obsolete with the development of LED lights.

Acetylene is also used in the production of several polyethene plastics. When ethyne is subjected to semi-hydrogenation, it is converted into ethylene (also known as ethene). The ethylene formed as a product from this reaction can be employed as a feedstock in the polymerization reactions that afford polyethene as the final product.

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