2butyne

2-Butyne, or but-2-yne, is an organic compound with the formula C4H6. It is an internal alkyne in which the carbon–carbon triple bond joins the middle two carbons of a four-carbon chain, giving the symmetric structure CH3-C≡C-CH3. It is also known as dimethylacetylene.

Physically, 2-butyne is a colorless, flammable, volatile liquid that is relatively nonpolar. It is sparingly soluble in water but dissolves in many organic solvents. The compound is reactive as an alkyne and can participate in a range of addition reactions typical for alkynes.

Reactivity and uses are dominated by its internal triple bond. Catalytic hydrogenation can convert 2-butyne to cis-2-butene or, with full hydrogenation, to n-butane. Halogenation across the triple bond yields dihalogenated alkenes, and hydrohalogenation proceeds to give haloalkenes or further derivatives. Hydration of 2-butyne under acidic mercuric conditions furnishes 2-butanone (methyl ethyl ketone) after enol–keto tautomerization, making 2-butyne a convenient precursor in organic synthesis.

Preparation and occurrence are typical of internal alkynes. 2-Butyne can be prepared by double dehydrohalogenation of 2,3-dibromobutane using a strong base. It occurs in trace amounts in some fossil-fuel–derived streams and can be produced industrially as a chemical building block.

Safety and handling notes: as a volatile and flammable hydrocarbon, 2-butyne requires appropriate precautions to avoid ignition and inhalation hazards. It should be stored and handled with proper ventilation and compatible equipment.