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| Names | |
|---|---|
| Preferred IUPAC name
But-2-yne | |
| Other names
Dimethylacetylene | |
| Identifiers | |
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3D model (JSmol) |
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| ChEMBL | |
| ChemSpider |
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| ECHA InfoCard | 100.007.239 
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PubChem CID |
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| UNII | |
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). | |
2-Butyne (dimethylacetylene, crotonyleneorbut-2-yne) is an alkyne with chemical formulaCH3C≡CCH3. Produced artificially, it is a colorless, volatile, pungent liquid at standard temperature and pressure.
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.
2-Butyne can be synthesized by the rearrangement reactionofethylacetylene in a solution of ethanolic potassium hydroxide.[6]
2-Butyne, along with propyne, is used to synthesize alkylated hydroquinones in the total synthesisofVitamin E.[7]
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