What is an Acetylide?
Acetylide is a chemical compound with the chemical formulas MC≡CH and MC≡CM in organometallic chemistry, where M is a metal. The term is loosely defined and can refer to substituted acetylides with the general structure RCCM (where R is an organic side chain). Acetylides are organic synthesis reagents. Calcium acetylide, also known as calcium carbide, is a common commercial compound.
Acetylides of the type ${{R}{C}_{2}{M}}$ are widely used in organic chemistry for alkynylations. They are nucleophiles that react with a wide range of electrophilic and unsaturated substrates. The Favorskii reaction is a classic example. In the example below, ethyl propiolate is deprotonated by n-butyllithium to yield the corresponding acetylide. This acetylide reacts with cyclopentanone's carbonyl centre. The alkynyl alcohol is liberated during the hydrolytic process.
Structure and Bonding of Acetylide
Acetylide acquires ionic properties when it is bonded with an alkali metal or an alkaline earth metal. The hydrolysis of these compounds can confirm evidence for acetylide's ionic properties.
Hydrolysis of acetylide produces acetylene and metal oxide.
Acetylide has covalent properties when bonded with transition metals.
Acetylide has properties similar to its doubly substituted analogues.
Metal acetylide has a polymeric structure in the absence of a ligand, with the acetylide group acting as a bridging ligand.
Applications of Acetylide
Because of their high sensitivity to water, acetylides are used as explosives.
To detect the presence of acetylene, gaseous copper acetylide is passed through a copper (I) chloride solution.
Petrochemistry makes use of copper acetylide.
Inside pipes in industries are made of copper acetylide.
Acetylide is also used in organic synthesis to detect the presence of terminal alkynes.
Important Questions
1. How metal Acetylide is formed?
Ans: A metal acetylide is an alkyne in which a proton (hydrogen) has been removed from the terminal end by a metal such as sodium or organolithium. The alkyne $CH{≡}CH$, for example, could be deprotonated to form the acetylide ion${{C}{H}_{3}{≡}{C}^-}$. It becomes a strong nucleophile after being deprotonated. Some acetylides, such as silver or copper acetylide, are explosives. Acetylide ions are extremely useful in organic chemistry reactions involving the addition and substitution of carbon chains. Acetylides exhibit additional reactions with ketones to form tertiary alcohols as one type of reaction.
2. What is the formula of silver acetylide?
Ans: Silver acetylide, also known as a metal acetylide, is an inorganic chemical compound with the formula ${{Ag}_{2}{C}_{2}}$. The compound can be thought of as a salt of acetylene, a weak acid. The anion of the salt is made up of two carbon atoms connected by a triple bond. Although the analogous calcium compound ${{Ca}{C}_{2}}$ is known as calcium carbide, the alternate name "silver carbide" is rarely used. Silver acetylide is a highly explosive substance.
Multiple Choice Questions
1. Allylides contain
a) ${{C}^{4-}}$ ions
b) ${{C}^{2-}}$ - ions
c) ${{C}^{3-}}$- ions
d) None of the above
Answer: (a)
2. Which of the following is called acetylide?
(a)${{C}_{12}{H}_{14}{Cl}{F}_{2}{NO}_{4}{S}}$
(b)${{C}_{3}{H}_{12}}$
(c)${{C}_{4}{H}_{5}}$
(d)${{C}_{6}{H}_{6}}$
Answer: (a)
3. Which of the following is acetylide ion?
(a)${{C}^{2-}_{2}}$
(b)${{C}^{3-}_{4}}$
(c)${{C}^{3-}_{2}}$
(d)${{C}^{4-}_{4}}$
Answer: (a)
Conclusion
Acetylide is a chemical compound class in which a metal is bonded to an alkyne. Acetylide has the general formula RC≡CM, where R is an organic side chain. Acetylide acquires ionic properties when it is bonded with an alkali metal or an alkaline earth metal. The hydrolysis of these compounds can confirm evidence for acetylide's ionic properties. Because of their high sensitivity to water, acetylides are used as explosives. To detect the presence of acetylene, gaseous copper acetylide is passed through a copper (I) chloride solution.
FAQs on Acetylide: An Organic Compound
1. Why Silver articles become black when exposed to air?
When silver articles are exposed to air for an extended period of time, they turn black. When silver articles are exposed to air, the silver reacts with the sulphur in the air to form a black layer of silver sulphide on the surface. When silver is exposed to air, it turns black after a while. This is due to the silver metal reacting with sulphur in the atmosphere to form silver sulphide. As a result, a layer of silver sulphide forms on the surface of silver articles, making them appear dull and black.
2. How Silver Acetylide is formed?
Silver acetylide can be extracted by passing acetylene gas through a silver nitrate solution:
${{2}{Ag}{NO}_{3} {+} {C}_{2}{H}_{2} \to {Ag}_{2}{C}_{2} {+} {2}{H}{NO}_{3}}$
The precipitate produced by the reaction is greyish to white. Berthelot used the same synthesis in which he discovered silver acetylide in 1866. In acidic or neutral silver nitrate solutions, the double salt is formed. The formation of the double salt is prevented when the synthesis is carried out in basic ammonia solution, yielding pure silver acetylide. Acetylene gas is passed through a dilute silver nitrate and nitric acid solution to properly form the double salt.
Instead of passing acetylene gas through silver nitrate solution, a purer and whiter precipitate can be formed by passing acetylene gas through acetone and dropping the acetylene solution into a dilute silver nitrate and nitric acid solution. The reaction was carried out at room temperature.
3. What is sodium acetylide?
Sodium Acetylide is available in a variety of shapes and sizes, including ingot, foil, rod, plate, and sputtering target. Carbide powder, submicron powder, and nanoscale, single crystal or polycrystalline forms are also high purity forms. Most volumes of sodium acetylide are readily available. When applicable, American Elements produces many standard grades, including Mil Spec (military grade); ACS, Reagent, and Technical Grade; Food, Agricultural, and Pharmaceutical Grade; Optical Grade, USP, and EP/BP (European Pharmacopoeia/British Pharmacopoeia).
