1-Butyne
1-Butyne, chemically known as but-1-yne or ethylacetylene, is a terminal alkyne hydrocarbon with the molecular formula C₄H₆ and structural formula CH₃CH₂C≡CH.[1][2] It features a carbon-carbon triple bond between the first and second carbon atoms, rendering the attached terminal hydrogen acidic and enabling distinctive reactivity typical of terminal alkynes.[1] This compound appears as a colorless gas with a characteristic odor and exhibits key physical properties including a boiling point of 8 °C, a melting point of -126 °C, and a density of 0.678 g/cm³ at 0 °C.[3][4] Its molecular weight is 54.09 g/mol, and it has a CAS number of 107-00-6.[2] Due to the triple bond, 1-butyne is highly reactive, participating in reactions such as hydrogenation, metathesis, and condensations, which underpin its utility in chemical processes.[5] 1-Butyne serves as a versatile starting material in organic synthesis, particularly for constructing larger molecules in the pharmaceutical and chemical industries, and as a specialty gas for instrument calibration.[4][5] However, it presents significant hazards: it is an extremely flammable gas that may explode if heated under pressure, with vapors capable of causing dizziness, asphyxiation, or irritation upon inhalation or contact.[1][6] Proper handling requires ventilation, protective equipment, and avoidance of ignition sources.[6]Properties
Physical properties
1-Butyne has the molecular formula C₄H₆ and the structural formula HC≡C-CH₂-CH₃, consisting of a linear carbon chain with a terminal triple bond between the first and second carbon atoms.[1] At standard temperature and pressure, 1-butyne exists as a colorless gas with a characteristic acetylenic odor.[1][5]| Property | Value | Conditions/Notes |
|---|---|---|
| Boiling point | 8.1 °C | Normal boiling point[5] |
| Melting point | -125.7 °C | Normal melting point[5] |
| Density | 0.678 g/cm³ | At boiling point[5] |
| Vapor pressure | 1.65 bar | At 20 °C[7] |
| Critical temperature | 191 °C | Estimated critical point[8] |