Acetylide

What is an Acetylide?

Acetylide refers to a class of chemical compounds in which metal is bonded with an alkyne. The general formula of acetylide is RC≡CM, where R is an organic side chain.

Acetylide is a well-known reagent used in the synthesis of organic compounds. They are also formed as an intermediate in the coupling reactions.

Table of Content

• Structure and Bonding of Acetylide
• Synthesis of Acetylide
• Favorski Reaction
• Coupling Reaction
• Reactions of Acetylide
• Applications of Acetylide
• Frequently Asked Questions – FAQs

Structure and Bonding of Acetylide

• When acetylide is bonded with an alkali metal or an alkaline earth metal, it exhibits ionic properties. The hydrolysis of these compounds can verify evidence for the ionic properties of acetylide.
• Acetylide hydrolyse to form acetylene and metal oxide.
• When acetylide is bonded with transition metals, it exhibits covalent properties.
• Acetylide exhibits similar properties to its doubly substituted analogues.
• In the absence of ligand, metal acetylide exhibits polymeric structure, where the acetylide group is a bridging ligand.

Synthesis of Acetylide

From Alkyne

• Organometallic or inorganic superbases are used to synthesise acetylide from alkynes.
• Liquid ammonia is used to synthesise acetylide from alkenes.
• Ethereal solvents are also used to synthesise acetylide from alkenes.

RC≡CH + R-M ⇌ R-H + RC≡CM

• Lithium amide, LiHMDS and organolithium reagents like ethyl lithium are generally used to synthesise lithium acetylide.

• Inorganic reagents like sodium amide are generally used to synthesise sodium or potassium acetylide at room temperature and atmospheric pressure.
• Copper chloride is passed through acetylene to synthesise copper(I) acetylide.
• Silver nitrate is generally used to synthesise silver acetylide.
• To produce calcium carbide, lime, i.e. calcium oxide is heated with carbon at approximately 2,000°C.
• To produce lithium carbide, lithia, i.e. lithium oxide is heated with carbon at approximately 2,000°C.
• A strong base like KOH reacts with acetylene to form potassium acetylide.

HC≡CH + KOH ⇌ HC≡CK + H₂O

Further reaction with alcohol or an aldehyde yields a favorski product, i.e. propargyl alcohol.

• N-butyllithium deprotonates ethyl propiolate to synthesise the corresponding acetylide.
• Acetylide is also formed as an intermediate in coupling reactions.

What is a Favorski Reaction?

The Favorski reaction is a chemical reaction between an alkyne and a carbonyl compound under the strongly basic conditions to yield alkynol.

It was discovered in the early 1900s by a Russian chemist, Alexei Favorski.

What is a Coupling Reaction?

A reaction involving the joining of two chemical species is known as a coupling Reaction.

• A reaction between organic halide and the organometallic compound is an example of a coupling reaction.

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Reactions of Acetylide

• Acetylide is used in alkynylation reactions in organic chemistry.
• Acetylide acts as a nucleophile in various electrophilic and unsaturated substrate reactions.

Applications of Acetylide

• Acetylides are used as explosive due to its high sensitivity to water.
• Gaseous copper acetylide is passed to a copper (I) chloride solution to test the presence of acetylene.
• Copper acetylide is used in petrochemistry.
• Copper acetylide is used to form inside pipes in industries.
• Acetylide is also used to test the presence of terminal alkynes in organic synthesis.