Acetylene

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What is Acetylene?

Acetylene is the chemical compound, having the formula as C2H2. It is the simplest alkyne and is a hydrocarbon. Acetylene is a colorless gas (in general, the lower hydrocarbons are gaseous in nature), which is used as a chemical building block widely and also as a fuel. In the pure form of acetylene, it is unstable, and therefore, it is usually handled as a solution. Pure acetylene is odorless, but, usually, the commercial grades have a marked odor because of impurities. The systematic C2H2 name can be given as ethyne.


Acetylene is unsaturated as an alkyne because its two carbon atoms are together bonded in a triple bond. The carbon-carbon triple bond places all the four atoms in a similar straight line, with the CCH bond angles, as 180°.


Formula and Structure of Acetylene

The chemical formula of acetylene is C2H2, and its extended formula is CH≡CH. The molar mass of acetylene can be given as 26.04 g/mol-1. Besides, this is the simplest alkyne molecule, which is a functional group that is characterized by scientists, having triple bonds.


Its molecules are linear 180 degrees, with its carbon atoms hybridized sp, consequently. Also, both carbons have 2 sp orbitals, on which, one bond to the hydrogen and the other bonds to the carbons simple bond. On the other side, the triple bond, that is 2  bonds, that produce between the four P orbitals without hybridization, that lies orthogonal to the linear system.


In a common representation used for organic molecules, its chemical structure is represented as C2H2, and the acetylene structure or the C2H2 structure can be given as follows.


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Occurrence of Acetylene

We can find the occurrence of acetylene in nature, especially dissolved in water. A few bacteria use it as the main source in the production of acetaldehyde. We can also find this compound in natural gas and in oil wells together with crude oil and the other gases. Moreover, it is also a part of some atmosphere of the solar planet.


Production of Acetylene

Since the year 1950, acetylene has been synthesized by the partial combustion of CH4 (which is methane). Until 1983, around 4,00,000 tonnes were produced.


It was prepared by a reaction, discovered by Friedrich Wohlerthe in 1862. The hydrolysis of calcium carbide reaction can be given as follows:

CaC2 + 2H2O → Ca(OH)2 + C2H2

The reaction represented above takes place at an extremely high temperature at temperature, approximately 2000 °C, by using an electric arc furnace.


Acetylene Properties

Let us discuss the physical and chemical acetylene properties.


Physical Properties

Acetylene is a colorless gas, which has a garlic-like odor, but it has the purest form as odorless. We dissolve the compound in acetone to ship. The Melting point (more precisely triple point, due to the equilibrium between the three phases) and sublimation (process of converting the solid to gas and vice versa without going via the liquid state) points are -80.7℃ and -84.7℃, respectively.


The density of acetylene can be given as 1.097 g/mL-1. One can easily ignite a sooty flame. However, acetylene is miscible in acetone, water, benzene, and chloroform. It is also slightly soluble in ethanol.


Chemical Properties

Acetylene is a highly reactive chemical compound owing to its electrons in the C-C triple bond. That is why acetylene is a brilliant nucleophile. Thus, it can suffer a wide variety of reactions to obtain commercial products, such as acrylic acid, acetylide, alcohol, and a vinyl compound. We can also use it to obtain organometallic compounds when reacting with a metal such as copper.


Uses of Acetylene

Many industries use acetylene widely in the welding processes because of the high temperature of acetylene flames (3300℃). Some of the countries, which are less developed, use this flame as incandescent lighting. Also, it can provide intermediates as ethylene, which is very useful in the production of polypropylene, obtained by the plastic industry.


Applications of Acetylene

Portable Lighting

The calcium carbide was used to generate acetylene, which is used in the lamps either for portable or remote applications. It was used for cavers and miners before the widespread use of incandescent lighting; it is still used by the mining industries in a few nations without the workplace safety laws; many years later, low-power or high-lumen LED lighting. Also, the carbide lamps were extensively used as headlights in early motor vehicles and as an early light source for the lighthouses.


Health and Safety Hazards

Let us look at some important health and safety hazards that are linked with acetylene.

This compound is lighter than air and is just toxic when produced by the methods that can leave other chemical compounds as impurities. Also, it ignites easily with a sooty flame. Besides, it should not be stored with oxidizing agents together. Most notably, it explodes when exposed to heat or fire.

FAQ (Frequently Asked Questions)

1. Is Acetylene Corrosive to a Metal?

Ans: Acetylene is a colorless compound in its pure form, and it has a good scent. While it has many functions, acetylene is now referred to as being capable of inhibiting the top-line corrosion that usually occurs in gas pipelines. Acetylene can be sprayed as a corrosion inhibitor, owing to its high volatility.

2. What Happens if we Inhale Acetylene?

Ans: The symptoms of inhalation of acetylene can result in fatigue, dizziness, tiredness, vomiting, nausea, tachypnea, and tachycardia. High-level exposure to acetylene will lead to a loss of consciousness and also death, sometimes. Acetylene is also a colourless gas, which is widely used in welding processes.

3. Why is Ethyne Called Acetylene?

Ans: The name acetylene was invented by the French chemist, named “Marcelin-Pierre-Eugène Berthelot” (1823-1907) in the year 1864, from the French acétylène. This compound was derived from the chemical ending with “ene + acetyl,” which the German chemist Justus von Liebig, coined of acetic in 1839.

4. List Out Some Acetylene Uses?

Ans: Let us look at some of the acetylene gas uses.

  • Acetylene is used in the glass industry.

  • It is used in brazing.

  • Used in the manufacturing of a synthetic rubber.

  • Used as an additive to preserve food items.

  • Used to precipitate metals.

  • Used in soldering metals.

  • Used in the manufacturing of an acetic acid.

  • Used in carburization of steel.

  • It is also used as a feedstock in the manufacturing of acrylonitrile.

  • Used as a fuel additive.