What Is Acetylene? Detailed Explanation for Students
Any group of organic chemical compounds is made up only of the atoms carbon (C) and hydrogen (H). The carbon atoms bind together to form the compound's framework, and the hydrogen atoms adhere to it in a variety of ways. Petroleum and natural gas are mostly made up of hydrocarbons.
Alkanes, alkenes, and alkynes are the three main families of aliphatic hydrocarbons based on the sorts of bonds they include. Alkanes have just single bonds, whereas alkenes and alkynes have a carbon-carbon double bond and a carbon-carbon triple bond, respectively.
Now we have a basic understanding of hydrocarbons and we are ready to explore acetylene. Further in this topic, we will go through some acetylene properties and acetylene formulas.
What is Acetylene?
Acetylene is the simplest alkyne chemical molecule, with the formula C2H2. Acetylene is also known by the names Ethyne, Narcylen, and Vinylene. It is widely employed as a chemical component and a fuel. It is handled as a solution in its pure form, which is unstable. It is an unsaturated molecule in which the two carbon atoms are joined by a triple bond.
Acetylene Formula
As we discussed that acetylene is the first simplest alkyne. As it is an unsaturated hydrocarbon so it must have at least two carbon atoms bonded with each other to make an unsaturated hydrocarbon or we can say a triple bond. As it is the simplest alkyne so it has exactly two carbon atoms.
As we know Alkyne has a general formula as CnH2n-2.
So for acetylene n=2.
Hence acetylene formula =× C2H2×2-2=C2H2
As per the IUPAC Nomenclature of Organic Compounds, For alkyne, we have to add “yne” as a suffix with the prefix according to the number of carbon atoms in the molecule.
So by this rule, the IUPAC name of acetylene is “Eth(prefix for 2 carbons)+yne(suffix for alkyne)”. IUPAC name of acetylene is “Ethyne”.
Acetylene Properties
Vinylene is a colourless gas with a faint ether odour. Water, chloroform, acetone, and benzene are all easily soluble in this compound. Carbon disulfide and ethanol just marginally dissolve it. It burns easily and is lighter than air. Containers can be dramatically ruptured by prolonged exposure to heat or fire.
Acetylene cannot exist as a liquid at atmospheric pressure and has no melting point. The melting point (80.8 °C) at the minimum pressure at which liquid acetylene can exist is shown by the triple point on the phase diagram (1.27 atm). Sublimation can convert solid acetylene to vapour (gas) at temperatures below the triple point. At atmospheric pressure, the sublimation point is 84.0 °C.
Acetylene is 27.9 g per kg soluble in acetone at normal temperature. The solubility of the same amount of dimethylformamide (DMF) is 51 g. At 20.26 bar, the solubility of acetone and DMF increases to 689.0 and 628.0 g, respectively. In pressurised gas cylinders, these solvents are employed.
Acetylene C2H2 Structure
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Use of Acetylene
Welding
Due to the high temperature of the flame, the industrial gases industry supplies around 20% of acetylene for oxyacetylene gas welding and cutting. Acetylene produces a flame of nearly 3,600 K (3,330 °C; 6,020 °F) when combined with oxygen, releasing 11.8 kJ/g. The hottest burning common fuel gas is oxyacetylene. The Oxyacetylene formula is also C2H2. After dicyanoacetylene's 5,260 K (4,990 °C; 9,010 °F) and cyanogen's 4,798 K (4,525 °C; 8,177 °F), acetylene is the third-hottest natural chemical flame. In former decades, oxy-acetylene welding was a prominent welding method. For many applications, the advancement and benefits of arc-based welding methods have rendered oxy-fuel welding obsolete. Welding using acetylene has become far less common. In regions where electricity is not widely available, oxyacetylene welding can be employed. Many metal fabrication shops employ oxyacetylene cutting.
Portable Lighting
The acetylene utilised in the lamps for portable or remote applications was generated using calcium carbide. It was used for miners and cavers before the widespread usage of incandescent lighting; or, many years later, low-power/high-lumen LED illumination; and it is currently used by mining industries in some countries where workplace safety standards do not exist. Carbide lamps were also widely employed as headlights in early automobiles and as a light source for lighthouses in the early 1900s.
Plastics and Acrylic Acid Derivatives
Acetylene can be converted to ethylene and used as a feedstock for a range of polyethene polymers. Acetylene's conversion to acrylic acid derivatives is another important application, particularly in China. Acrylic fibres, glasses, paints, resins, and polymers are all made from these compounds.
Niche Applications
When a steel piece is too large to put into a furnace, acetylene is occasionally used to carburize (harden) it. In radiocarbon dating, acetylene is utilised to volatilize carbon. In a small specialised research furnace, carbonaceous material in an archaeological sample is treated with lithium metal to generate lithium carbide (also known as lithium acetylide). The carbide can then be treated with water to produce acetylene gas, which can be fed into a mass spectrometer to determine the carbon-14 to carbon-12 isotope ratio.
Preparation of Acetylene
This chemical has been produced by partial combustion of CH2 since 1950. (methane). Until 1983, around 4,00,000 tonnes were produced. Friedrich Wohler discovered the reaction in 1862, and it was used to make it. The reaction of calcium carbide hydrolysis is as follows:
Ca(OH)2 + C2H2→CaC2 + 2H2O
The foregoing reaction takes place in an electric arc furnace at a very high temperature of roughly 2000 °C.
Health Hazards Due to Acetylene
People who come into touch with this chemical may experience headaches, dizziness, and loss of consciousness. Choking death can occur if there is a significant concentration of Ethyne in the air.
FAQs on Acetylene (C2H2): Properties, Structure & Applications
1. What is Acetylene (C₂H₂) and what is its official IUPAC name?
Acetylene is the common name for the simplest member of the alkyne family of hydrocarbons. Its chemical formula is C₂H₂. According to the IUPAC naming system, its official name is ethyne. It is a colourless gas, widely known for its use in welding and cutting.
2. What does the structure of an acetylene molecule look like?
The acetylene molecule has a simple, linear structure. It consists of two carbon atoms joined by a triple bond (one sigma and two pi bonds) and one hydrogen atom attached to each carbon atom. Due to sp hybridisation of the carbon atoms, all four atoms lie in a straight line, with a bond angle of 180°.
3. How is acetylene typically prepared in a laboratory?
A common and straightforward method for preparing acetylene in the lab is by the reaction of calcium carbide (CaC₂) with water. When water is dripped onto calcium carbide, a vigorous reaction occurs, producing acetylene gas and calcium hydroxide. The chemical equation is: CaC₂ + 2H₂O → C₂H₂ + Ca(OH)₂.
4. What are the most important uses of acetylene gas?
Acetylene has several significant industrial applications. The most common uses include:
- Oxy-acetylene welding and cutting: When burned with oxygen, it produces a flame with a very high temperature (over 3300°C), which can easily melt steel.
- Chemical synthesis: It serves as a starting material for producing many other organic chemicals, such as vinyl chloride (for PVC plastics), acetaldehyde, and acetic acid.
- Portable lighting: In the past, it was used in carbide lamps for mining and lighthouses because it burns with a bright, luminous flame.
5. Why is acetylene (ethyne) considered acidic while ethane and ethene are not?
This difference in acidity comes down to the hybridisation of the carbon atoms. In acetylene, the carbon atoms are sp hybridised, which has 50% s-character. The high s-character pulls the electron density of the C-H bond closer to the carbon atom. This makes it easier for the hydrogen atom to be released as a proton (H⁺), making acetylene weakly acidic.
6. How does acetylene react with certain metals like copper or silver?
Due to its acidic nature, the hydrogen atoms in acetylene can be replaced by certain metal ions. When acetylene is passed through a solution containing copper or silver salts, it forms unstable and explosive compounds called metal acetylides (e.g., copper acetylide or silver acetylide). This is why acetylene is never stored in containers made of copper or silver alloys.
7. What happens when acetylene gas is passed through a red-hot iron tube?
When acetylene is passed through a red-hot iron tube at a high temperature (around 873 K), it undergoes a process called cyclic polymerisation. In this reaction, three molecules of acetylene join together to form one molecule of benzene (C₆H₆), a stable aromatic compound. This is a classic method for synthesising benzene from an aliphatic compound.
