1Butyne

1-Butyne, also known as but-1-yne, is an organic compound with the formula C4H6. It is the simplest terminal alkyne, featuring a triple bond between the first and second carbon: CH≡C-CH2-CH3.

Preparation and occurrence: In laboratory settings, 1-butyne is typically prepared by double dehydrohalogenation of a 1,2-dihalobutane (for example, 1,2-dibromobutane) using strong bases such as sodium amide (NaNH2) or potassium hydroxide in ethanol. It can also be formed in situ from propargyl halides. 1-Butyne is not common in nature and is mainly produced as a reactive building block for organic synthesis.

Physical and chemical properties: 1-Butyne is a colorless, volatile, flammable hydrocarbon. It is a gas at room temperature and is soluble in organic solvents but essentially insoluble in water. The terminal hydrogen is relatively acidic (pKa around 25), allowing deprotonation to form acetylide anions with strong bases such as organolithiums or NaNH2. Like other alkynes, it participates in typical alkyne reactions, including electrophilic additions to form vinyl halides, acid-catalyzed hydration to give 2-butanone, and hydroboration-oxidation to yield butanal. Catalytic hydrogenation yields butane, and the compound can undergo various coupling reactions after formation of metal acetylide intermediates.

Applications: 1-Butyne serves as a versatile building block in organic synthesis, enabling the introduction of an ethynyl fragment into larger molecules. It is used in studies of alkyne chemistry and as a precursor to carbonyl compounds via hydration and related oxidation routes.

Safety: 1-Butyne is highly flammable and handling requires proper ventilation and standard flammable-chemical precautions.