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2-Butyne

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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2-Butyne12
H 3 C − C ≡ C − CH 3 {\displaystyle {\ce {H3C-C#C-CH3}}}
Ball-and-stick model
Ball-and-stick model source ↗
Names
Preferred IUPAC name
But-2-yne
Other names
Dimethylacetylene
Crotonylene
Identifiers
3D model (JSmol)
ChEMBL
ChemSpider
ECHA InfoCard 100.007.239
UNII
  • InChI=1S/C4H6/c1-3-4-2/h1-2H3 checkY
    Key: XNMQEEKYCVKGBD-UHFFFAOYSA-N checkY
  • InChI=1/C4H6/c1-3-4-2/h1-2H3
    Key: XNMQEEKYCVKGBD-UHFFFAOYAO
  • CC#CC
Properties
C4H6
Molar mass 54.092 g·mol−1
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).
checkY verify (what is checkY☒N ?)

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 infrared spectrum3 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 Group45 G36 shows that one would need to analyse its high resolution rotation-vibration Raman spectrum to determine its equilibrium structure. Pulsed-field-ionisation zero-kinetic-energy (PFI-ZEKE) photoelectron spectra of 2-butyne and its fully deuterated isotopomer have been recorded and analysed.6

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.7

Applications

2-Butyne, along with propyne, is used to synthesize alkylated hydroquinones in the total synthesis of Vitamin E.8

See also

See also

References

References

  1. [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. Jacovella, Ugo; et al. (2015). "Internal rotation, spin–orbit coupling, and low-frequency vibrations in the ground state of CH3–CC–CH+3 and CD3–CC–CD+3". Mol. Phys. 113: 2115. doi:10.1080/00268976.2015.1005708. hdl:20.500.11850/182812.
  7. 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.
  8. 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.