Ethyne - Structure, Formula, Application, FAQs

Edited By Team Careers360 | Updated on Jul 02, 2025 04:48 PM IST

Ethyne is also known as acetylene and has the chemical formula of C₂H₂. Ethyne is a hydrocarbon ( it contains hydrogen and carbon). It also occupies the position of the simplest alkyne. Ethyne does not contain any colour as it is colourless gas as generally lower members of hydrocarbon remains in gaseous form. Most important and widely used of Ethyne is in the fuels and chemical sector. In pure form, acetylene or Ethyne will be odourless but due to the presence of some impurities like divinyl sulphide or phosphine, the compound usually shows odour. As we can easily notice that the compound acetylene is unsaturated due to the presence of a triple bond between adjacent carbon atoms.

This Story also Contains

Ethyne to Ethane
Ethane to Ethyne
Hydrolysis of Calcium Carbide
Applications of Acetylene:-
Combustion of Ethyne
Ethyl Acetylene

Q- Ethyne structural formula

CH₂=CH₂ also known as acetylene, it is a hydrocarbon.

C₂h₂ is Produced by Hydrolysis of ?

Answer will be calcium carbide as calcium carbide when reacts with water ( hydrolysis of calcium carbide) forms Ethyne and calcium hydroxide ( lime milk )

CaC₂ + 2 H₂O ? C₂ H₂ + Ca(OH)₂

Q- Combustion of ethyne ?

When we do combustion of ethyne then it will form a clean flame with high temperature and high energy contents which will be used by us in oxyacetylene welding, or for cutting metals and many more uses are these in chemical sectors, mechanical sectors , etc.

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Ethyne to Ethane

To convert ethane which is a saturated hydrocarbon from ethyne i.e. unsaturated hydrocarbon we will have to do hydrogenation 2 times to convert ethyne to ethane .

Q- C₂h₂ name

c₂h₂ or CH₂=CH₂ is known as ethyne or acetylene and it is a organic compound made up of carbon and hydrogen. There is a triple bond present between adjacent c atoms of ethyne.

Ethane to Ethyne

To convert ethane to ethyne, first we had to convert ethane to bromoethane with the help of a proper catalyst.

CH₂=CH₂+Br₂→CH₂(Br)−CH₂(Br)

1,2a − dibromoethane

And then reaction of dibromo ethane with alcoholic koh will led to the formation of ethyne

CH₂Br−CH₂Br alc.KOH CH₂=CHBrNaNH₂CH≡CH ethyne

Q- Formula of acetylene ?

H-C≡C-H

Hydrolysis of Calcium Carbide

Ca C₂ + 2 H₂O --> C₂ H₂ + Ca(OH)₂

In the above reaction, we can easily notice that calcium carbide reacts with water to form ethyne and calcium hydroxide , we have to note that the solubility of acetylene will increase with the increase of pressure.

Applications of Acetylene:-

About 20% of the formed acetylene is being transferred to industries for oxyacetylene gas welding and cutting. It can be used in oxyacetylene welding because flame produced by acetylene has a very high-temperature I.e.3,600 K (3,330 °c) and releasing 11.8 kJ/g. Flame will be produced through the combustion of acetylene in the presence of oxygen. Acetylene occupies the position of 3^rd hottest chemical flame which is provided in nature. Its main role in oxyacetylene welding is for many decades. Oxyacetylene welding products are also very versatile. Oxyacetylene welding can also be used in the place where electricity is not properly available.

Nowadays many shops use oxyacetylene in the cutting of metals. And for this merchants must need to balance proper pressure with the help of a regulator and the pressure used in cutting and weldings generally more than 15 psi. If pressure is not controlled properly then there will be a shockwave that causes acetylene to decompose into hydrogen and carbon explosively.

Acetylene or ethyne is also used as a portable lighter by miners and cavers. Carbide lamps are also used as headlights in vehicles and as a light source in lighthouses.We can get polyacetylene films by polymerisation of ethyne with ziegler natta catalyst.It is also interesting to note that polyacetylene was the first reported semiconductor with a chain of CH centres and having alternate single and double bonds in their structures. Reaction of ethyne with iodine will give a highly electrical conductive substance. One adverse effect to use oxyacetylene is that they produce products such as acrylic fibres, glasses, paints, resins, and polymers which are very harmful to the environment.

Acetylene has enough energy richness due to its structure I.e. C≡C triple bond. And also acetylene is highly soluble in water and thus makes a suitable substrate for bacteria and till now we have found a number of bacteria that are living in acetylene. Let us see how acetylene in water I.e. acetaldehyde is a suitable substrate for bacteria:-

C₂H₂ + H₂O → CH₃CHO

The enzyme that will catalyses the above reaction is

Acetylene Hydratase.

Q- Calcium carbide to ethyne ?

Ca C₂ + 2 H₂O --> C₂ H₂ + Ca (OH)₂

Related Topics link,

Q- how is ethyne produced from calcium carbide?

By hydrolysis of calcium carbide

Ca C₂ + 2 H₂O --> C₂ H₂ + Ca (OH)₂

Combustion of Ethyne

When ethyne burns then it will give a clean flame with high energy and temperature that will be used in various processes like oxyacetylene welding ,etc.

Hybridization of Athyne

Ethyne contains 3 bonds in which one sigma bond, i.e. formed by sp hybridized orbitals, is stronger than other two pi bonds. As we know pi bonds do not play any role in hybridization.

Also Read:

Ethyl Acetylene

Q Uses of Ethyne

Ethyne has been heavily used in oxyacetylene welding for many decades. Oxyacetylene welding products are also very versatile. Oxyacetylene welding can also be used in the place where electricity is not properly available. Nowadays many shops use oxyacetylene in the cutting of metals. And for this merchants must need to balance proper pressure with the help of a regulator and the pressure used in cutting and weldings generally more than 15 psi. If pressure is not controlled properly then there will be a shockwave that causes acetylene to decompose into hydrogen and carbon explosively. Acetylene or ethyne is also used as a portable lighter by miners and cavers. Carbide lamps are also used as headlights in vehicles and as a light source in lighthouses.

We can get polyacetylene films by polymerisation of ethyne with ziegler natta catalyst. It is also interesting to note that polyacetylene was the first reported semiconductor with a chain of CH centres and having alternate single and double bonds in their structures. Reaction of ethyne with iodine will give a highly electrical conductive substance.

Q- Acetylide Formula ?

Acetylide is a chemical compound with chemical formulas MC≡CH and MC≡CM and bere M refers to any metal and C for Carbon.

Q- How to convert ethene to ethyne?

It is done by two steps:

1st step: Formation of dibromomethane in the reaction of ethene in the presence of CCl₄ and Br₂.

2nd step: Ethyne is formed by the reaction of dibromomethane in the presence of KOH.

Q. What is c2h2?

Acetylene.

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NCERT Chemistry Notes:

Frequently Asked Questions (FAQs)

1. What is ethyne and why is it important?

Ethyne, also known as acetylene, is the simplest alkyne hydrocarbon with the formula C2H2. It's important because of its unique triple bond structure and wide range of industrial applications, including welding, metal cutting, and as a precursor in organic synthesis.

2. What is the significance of ethyne's ability to form metal acetylides?

Ethyne's ability to form metal acetylides is significant because it allows for the production of various organic compounds. These acetylides are important intermediates in organic synthesis and can be used to form new carbon-carbon bonds.

3. Why is ethyne often stored dissolved in acetone?

Ethyne is stored dissolved in acetone for safety reasons. Pure ethyne can be explosive under pressure, but dissolving it in acetone stabilizes it and allows for safer storage and transport at higher pressures.

4. Why is ethyne considered a building block in organic synthesis?

Ethyne is a versatile building block in organic synthesis due to its triple bond reactivity. It can undergo addition reactions, be used in coupling reactions, and serve as a precursor for various organic compounds, making it valuable in the production of polymers, pharmaceuticals, and other chemicals.

5. What is the significance of ethyne's linear structure in its industrial applications?

Ethyne's linear structure contributes to its high flame temperature and concentrated heat output when burned. This makes it ideal for welding and cutting metals, as the heat can be focused precisely where needed.

6. What is the significance of ethyne's high heat of combustion?

Ethyne's high heat of combustion makes it valuable for welding and metal cutting. The triple bond stores a large amount of energy, which is released as intense heat when burned, producing temperatures up to 3,300°C.

7. How does the combustion of ethyne differ from that of other hydrocarbons?

Ethyne combustion is characterized by an extremely hot, concentrated flame with a high carbon-to-hydrogen ratio. This results in a sooty flame unless burned with pure oxygen, making it distinct from cleaner-burning hydrocarbons like methane.

8. Why is ethyne more difficult to liquefy than other hydrocarbons of similar molecular weight?

Ethyne is more difficult to liquefy due to its linear structure and weak intermolecular forces. The rod-like shape of ethyne molecules results in less surface area for van der Waals interactions, requiring more energy to overcome the gaseous state.

9. How does the triple bond in ethyne affect its infrared spectroscopy?

The triple bond in ethyne produces a characteristic strong absorption band in infrared spectroscopy around 3300 cm^-1. This is due to the C-H stretching vibration, which is influenced by the high s-character of the sp-hybridized carbon atoms.

10. How does the reactivity of ethyne with copper(I) ions differ from other hydrocarbons?

Ethyne reacts with copper(I) ions to form copper(I) acetylide, a reddish precipitate. This reaction is unique to terminal alkynes and is used as a test for their presence. Other hydrocarbons do not form such complexes with copper(I) ions.

11. How does the bond length in ethyne compare to that in ethane and ethene?

The carbon-carbon bond length in ethyne (120 pm) is shorter than in ethene (134 pm) and ethane (154 pm). This is due to the increased s-character and greater overlap of orbitals in the triple bond of ethyne.

12. How does the bond energy of the carbon-carbon triple bond in ethyne compare to double and single bonds?

The carbon-carbon triple bond in ethyne has higher bond energy (839 kJ/mol) compared to double bonds in ethene (614 kJ/mol) and single bonds in ethane (348 kJ/mol). This higher bond energy contributes to ethyne's stability and reactivity.

13. What is the hybridization of carbon atoms in ethyne and how does it affect the molecule's properties?

Carbon atoms in ethyne are sp-hybridized. This hybridization results in a linear geometry, high s-character in the C-H bonds (leading to increased acidity), and a highly symmetrical electron distribution that contributes to ethyne's unique reactivity.

14. Why is ethyne a gas at room temperature despite having a higher molecular weight than ethane?

Ethyne is a gas at room temperature due to its linear structure and weak intermolecular forces. The triple bond creates a rod-like molecule with minimal surface area for interactions, resulting in lower boiling point compared to ethane, which has stronger van der Waals forces.

15. How does the electron density distribution in ethyne affect its dipole moment?

Ethyne has a symmetrical electron density distribution due to its linear structure and identical atoms. As a result, ethyne has no permanent dipole moment, making it a non-polar molecule despite the polarity of its individual bonds.

16. How does the pi bond in ethyne contribute to its reactivity?

The pi bonds in ethyne are electron-rich and extend above and below the molecular axis. This electron density makes ethyne susceptible to electrophilic addition reactions and allows it to act as a nucleophile in some reactions.

17. How does the structure of ethyne differ from other hydrocarbons?

Ethyne has a linear structure with a carbon-carbon triple bond, making it different from alkanes (single bonds) and alkenes (double bonds). This triple bond gives ethyne unique chemical properties and reactivity.

18. How does the acidity of ethyne compare to other hydrocarbons?

Ethyne is more acidic than other hydrocarbons due to its sp-hybridized carbons. The s-character of the orbital holding the H atom is higher, making the C-H bond more polar and the H atom more easily removed as H+.

19. How does the sp hybridization in ethyne affect its geometry?

The sp hybridization in ethyne results in a linear geometry with bond angles of 180°. Each carbon atom has two sp hybrid orbitals (used for sigma bonds) and two unhybridized p orbitals (used for pi bonds), creating the triple bond and linear shape.

20. How does ethyne participate in addition polymerization?

Ethyne can undergo addition polymerization to form polyacetylene, a conductive polymer. This process involves the opening of the triple bond and the formation of new single bonds between carbon atoms, creating a long chain with alternating single and double bonds.

21. How does ethyne behave in bromination reactions compared to ethene?

Ethyne undergoes bromination in two steps, first forming a dibromide (trans addition) and then a tetrabromide. This is in contrast to ethene, which forms only a dibromide. The stepwise addition in ethyne is due to its triple bond structure.

22. How does the reactivity of ethyne in hydrogenation compare to that of ethene?

Ethyne is more reactive in hydrogenation than ethene. It can undergo stepwise hydrogenation, first to ethene and then to ethane. This higher reactivity is due to the greater strain and electron density in the triple bond compared to the double bond in ethene.

23. How does the presence of a triple bond in ethyne affect its heat of hydrogenation?

The triple bond in ethyne results in a higher heat of hydrogenation compared to alkenes. The hydrogenation of ethyne to ethane releases more energy (311 kJ/mol) than the hydrogenation of ethene to ethane (137 kJ/mol), reflecting the greater stability gained by breaking the triple bond.

24. Why is ethyne more reactive than ethene in addition reactions?

Ethyne is more reactive in addition reactions because its triple bond is more electron-rich than ethene's double bond. This higher electron density makes ethyne more susceptible to electrophilic attack.

25. How does the electronegativity difference between carbon and hydrogen in ethyne affect its properties?

The small electronegativity difference between carbon and hydrogen in ethyne results in a slightly polar C-H bond. This contributes to ethyne's weak acidity and its ability to form hydrogen bonds, affecting its solubility and reactivity.

26. Why is ethyne sometimes called acetylene, and what's the significance of this name in industry?

Ethyne is commonly called acetylene in industry, derived from the words "acetic" and "wood." This name is significant as it reflects the historical production method from calcium carbide and water, and is widely used in industrial contexts, especially in welding and metal cutting.

27. How does the reactivity of ethyne with water compare to that of other hydrocarbons?

Ethyne reacts with water more readily than other hydrocarbons, forming acetaldehyde in the presence of mercury(II) salts (Kucherov reaction). This higher reactivity is due to the electron-rich nature of the triple bond and its susceptibility to nucleophilic attack.

28. How does the solubility of ethyne in water compare to other hydrocarbons?

Ethyne is slightly more soluble in water than other hydrocarbons due to its ability to form weak hydrogen bonds. The triple bond creates a slight negative charge on the molecule, allowing for some interaction with water molecules.

29. How does the electron configuration of ethyne contribute to its ability to form acetylide ions?

The sp-hybridized carbons in ethyne have a high s-character, making the terminal hydrogen slightly acidic. This allows ethyne to form acetylide ions (HC≡C^-) when reacted with strong bases, a property unique among hydrocarbons and important in many organic reactions.

30. What role does ethyne play in the production of vinyl chloride?

Ethyne is a key precursor in the production of vinyl chloride, which is used to make PVC plastic. The process involves the addition of hydrogen chloride to ethyne, followed by further reactions to produce vinyl chloride monomer.

31. What is the importance of ethyne in the production of synthetic rubber?

Ethyne is crucial in synthetic rubber production as it's used to synthesize chloroprene, the monomer for neoprene rubber. This process involves the dimerization of ethyne to form vinylacetylene, which is then converted to chloroprene.

32. Why is ethyne sometimes used as a ripening agent for fruits?

Ethyne can be used as a ripening agent because it mimics the effects of ethene (ethylene), a natural plant hormone that promotes ripening. Ethyne breaks down to form ethene in small quantities, triggering the ripening process in fruits.

33. What is the significance of ethyne's ability to form cyclic compounds?

Ethyne's ability to form cyclic compounds is significant in organic synthesis. Through reactions like the Reppe synthesis, ethyne can be used to create cyclooctatetraene and other cyclic molecules, which are important in various industrial and pharmaceutical applications.

34. Why is ethyne sometimes used in chemical vapor deposition processes?

Ethyne is used in chemical vapor deposition because it can decompose at high temperatures to form pure carbon. This property is utilized in creating carbon coatings, carbon nanotubes, and other carbon-based materials in various industrial applications.

35. What is the role of ethyne in the production of acetaldehyde?

Ethyne is used in the production of acetaldehyde through the Kucherov reaction. This process involves the hydration of ethyne using a mercury(II) catalyst, demonstrating ethyne's versatility as a precursor in organic synthesis.

36. How does the reactivity of ethyne with halogens compare to that of alkenes?

Ethyne reacts more vigorously with halogens than alkenes due to its higher electron density. The reaction can proceed in two steps, first forming a dihalide and then a tetrahalide, whereas alkenes typically form only dihalides.

37. Why is ethyne sometimes used as a fuel in specialized applications?

Ethyne is used as a fuel in specialized applications due to its high heat of combustion and ability to burn in pure oxygen. This makes it suitable for underwater welding torches and other situations where a concentrated, high-temperature flame is needed.

38. How does the structure of ethyne contribute to its ability to form polymers?

Ethyne's triple bond structure allows it to undergo addition polymerization, forming polymers with conjugated double bonds. This ability is crucial in the production of materials like polyacetylene, which has unique electrical properties.

39. What is the significance of ethyne's role in the synthesis of vitamins?

Ethyne plays a significant role in vitamin synthesis, particularly in the production of vitamin A and vitamin E precursors. Its versatile reactivity allows for the construction of complex molecular structures essential in these vitamins.

40. How does the bond angle in ethyne compare to other hydrocarbons, and why is this important?

The bond angle in ethyne is 180°, compared to 109.5° in alkanes and 120° in alkenes. This linear geometry is crucial for ethyne's reactivity, physical properties, and its ability to form specific types of compounds in organic synthesis.

41. Why is ethyne sometimes used in plasma chemistry applications?

Ethyne is used in plasma chemistry due to its ability to form carbon-rich plasmas. When subjected to high-energy conditions, ethyne can decompose and recombine to form various carbon structures, useful in creating carbon films and nanostructures.

42. How does the presence of a triple bond in ethyne affect its UV-visible spectroscopy?

The triple bond in ethyne results in a characteristic absorption in the UV region of the spectrum. This is due to the π→π* transition, which occurs at a higher energy (shorter wavelength) than in alkenes, reflecting the greater stability of the triple bond.

43. What is the importance of ethyne in the production of carbon black?

Ethyne is an important precursor in the production of carbon black, a form of amorphous carbon used in tires, inks, and plastics. The incomplete combustion of ethyne under controlled conditions produces high-quality carbon black with specific properties.

44. Why is ethyne sometimes used in the production of synthetic diamonds?

Ethyne is used in synthetic diamond production because it can be decomposed at high temperatures and pressures to form pure carbon. The carbon atoms can then be arranged into the diamond crystal structure under appropriate conditions.

45. How does the triple bond in ethyne affect its ability to act as a ligand in organometallic chemistry?

The triple bond in ethyne makes it an excellent ligand in organometallic chemistry. Its π-electrons can coordinate to metal centers, forming stable complexes. This property is utilized in various catalytic processes and in the synthesis of organometallic compounds.

46. What is the significance of ethyne's role in the production of acrylic acid?

Ethyne is a key starting material in the production of acrylic acid, an important industrial chemical. The process involves the reaction of ethyne with carbon monoxide and water, demonstrating ethyne's versatility in organic synthesis and its importance in the polymer industry.

47. Why is ethyne sometimes used in atomic absorption spectroscopy?

Ethyne is used as a fuel gas in atomic absorption spectroscopy because it produces a very hot flame when burned with air or oxygen. This high-temperature flame is effective in atomizing samples, allowing for sensitive detection of various elements.

48. How does the structure of ethyne influence its behavior in cycloaddition reactions?

The linear structure and π-electron system of ethyne make it an excellent dienophile in cycloaddition reactions, such as the Diels-Alder reaction. Its ability to participate in these reactions is crucial for synthesizing complex cyclic compounds in organic chemistry.

49. What is the importance of ethyne in the production of vinyl acetate?

Ethyne is a key precursor in the production of vinyl acetate, an important monomer used in various polymers and adhesives. The process involves the reaction of ethyne with acetic acid and oxygen over a palladium catalyst, showcasing ethyne's industrial significance.

50. How does the triple bond in ethyne affect its behavior in radical addition reactions?

The triple bond in ethyne can participate in radical addition reactions, forming vinyl radicals. This reactivity is important in various polymerization processes and in the synthesis of vinyl compounds. The high reactivity of the triple bond allows for stepwise addition of radicals.