diacetylene

Diacetylene, also known as butadiyne, is a hydrocarbon with the formula C4H2. It is the simplest member of the diynes, specifically a 1,3-diyne, consisting of two acetylene units linked by a single bond: HC≡C−C≡CH. The molecule is linear and highly unsaturated, with significant reactivity arising from the cumulated triple bonds.

Diacetylene is typically a colorless gas or a very volatile liquid at room temperature. It is unstable and readily undergoes polymerization when exposed to heat or light, forming long chains of poly(diacetylene).

In solid forms such as crystals or thin films, diacetylene can polymerize topochemically to give polydiacetylenes, compounds that have been studied for optical and electronic properties. Polydiacetylenes can exhibit color changes and are investigated for nonlinear optics and chemical sensing.

Industrial production generally involves coupling of acetylene molecules using metal catalysts. It can also be generated in organic synthesis by coupling and dehalogenation methods, though it is typically handled under controlled conditions due to its reactivity.

Diacetylene is flammable and highly reactive, with polymerization that can occur violently under heat or light. Concentrated forms can be shock-sensitive or explosive in the presence of impurities or oxidizers. Proper storage under inert conditions and away from heat and oxidizers is advised.

See also: Butadiyne; polydiacetylene; diynes.

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