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2-Butyne

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2-Butyne
H 3 C − C ≡ C − CH 3 {\displaystyle {\ce {H3C-C#C-CH3}}}
Ball-and-stick model
Names
Preferred IUPAC name But-2-yne
Other names Dimethylacetylene
Crotonylene
Identifiers
CAS Number
3D model (JSmol)
ChEMBL
ChemSpider
ECHA InfoCard 100.007.239 Edit this at Wikidata
PubChem CID
UNII
CompTox Dashboard (EPA)
InChI
  • InChI=1S/C4H6/c1-3-4-2/h1-2H3Key: XNMQEEKYCVKGBD-UHFFFAOYSA-N
  • InChI=1/C4H6/c1-3-4-2/h1-2H3Key: XNMQEEKYCVKGBD-UHFFFAOYAO
SMILES
  • C(#CC)C
Properties
Chemical formula 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 , 100 kPa). checkY verify (what is  ?) Infobox references
Chemical compound

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.

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 leads to a determination that the torsional barrier is only 6 cm (1.2×10 J or 72 J mol). However, it has not been determined whether the equilibrium structure is eclipsed (D3h) or staggered (D3d). Symmetry analysis using the Molecular Symmetry Group 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.

Synthesis

2-Butyne can be synthesized by the rearrangement reaction of ethylacetylene in a solution of ethanolic potassium hydroxide.

Applications

2-Butyne, along with propyne, is used to synthesize alkylated hydroquinones in the total synthesis of Vitamin E.

See also

References

  1. at Sigma-Aldrich
  2. NIST Chemistry WebBook page for 2-butyne
  3. di Lauro, C.; et al. (1997). "The rotation-torsion structure in the ν11/ν15 (Gs) methyl rocking fundamental band in dimethylacetylene". J. Mol. Spectrosc. 184 (1): 177–185. doi:10.1006/jmsp.1997.7321.
  4. Longuet-Higgins, H.C. (1963). "The symmetry groups of non-rigid molecules". Molecular Physics. 6 (5): 445–460. Bibcode:1963MolPh...6..445L. doi:10.1080/00268976300100501.
  5. P. R. Bunker (1964). "The Rotation-Torsion Wavefunctions of Molecules that have two Identical Rotors". Mol. Phys. 8: 81. doi:10.1080/00268976400100091.
  6. Victor von Richter; Hans Meerwein (1916). Organic Chemistry: Chemistry of the aliphatic series Vol. I: Smith's 3rd American Ed. Philadelphia: P. Blakiston's Sons & Co. p. 89.
  7. Reppe, Walter; Kutepow, N; Magin, A (1969). "Cyclization of Acetylenic Compounds". Angewandte Chemie International Edition in English. 8 (10): 727–733. doi:10.1002/anie.196907271.
Alkynes
Preparations
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