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2-Butyne
Chemical compound / From Wikipedia, the free encyclopedia
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2-Butyne (dimethylacetylene, crotonylene or but-2-yne) is an alkyne with chemical formula CH3C≡CCH3. Produced artificially, it is a colorless, volatile, pungent liquid at standard temperature and pressure.
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Names | |
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Preferred IUPAC name
But-2-yne | |
Other names
Dimethylacetylene Crotonylene | |
Identifiers | |
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3D model (JSmol) |
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ChEMBL | |
ChemSpider |
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ECHA InfoCard | 100.007.239 ![]() |
PubChem CID |
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CompTox Dashboard (EPA) |
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Properties | |
C4H6 | |
Molar mass | 54.0904 g/mol |
Density | 0.691 g/mL |
Melting point | −32 °C (−26 °F; 241 K) |
Boiling point | 27 °C (81 °F; 300 K) |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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2-Butyne is of interest to physical chemists because of its very low torsional barrier and the problem of determining that barrier using high-resolution infrared spectroscopy. Analysis of its spectrum[3] leads to a determination that the torsional barrier is only 6 cm−1 (1.2×10−22 J or 72 J mol−1). However, it has not been determined whether the equilibrium structure is eclipsed (D3h) or staggered (D3d). Symmetry analysis using the Molecular Symmetry Group[4][5] G36 shows that one would need to analyse its high resolution rotation-vibration Raman spectrum to determine its equilibrium structure.
2-Butyne (dimethylethyne) forms with 5-decyne (dibutylethyne), 4-octyne (dipropylethyne) and 3-hexyne (diethylethyne) a group of symmetric alkynes.