# 2-Butyne
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> Markdown URL: https://mediated.wiki/source/2-Butyne.md
> Source: https://en.wikipedia.org/wiki/2-Butyne
> Source revision: 1355824404
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{{Short description|Alkyne with four carbon atoms}}
{{chembox
| verifiedrevid = 403365671
| Reference=[[https://www.sigmaaldrich.com/US/en/product/aldrich/254339] at [Sigma-Aldrich](/source/Sigma-Aldrich)][[http://webbook.nist.gov/cgi/cbook.cgi?ID=C503173 NIST Chemistry WebBook page for 2-butyne]]
| Name = 2-Butyne
| ImageFile1 = H3C-C#C-CH3
| ImageSize1 = 180px
| ImageName1 = Structural formula
| ImageFile2 = 2-butyne-3D-balls-B.png
| ImageSize2 = 150px
| ImageName2 = Ball-and-stick model
| ImageClass2 = bg-transparent
| PIN = But-2-yne
| OtherNames = Dimethylacetylene
Crotonylene
|Section1={{Chembox Identifiers
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| ChemSpiderID = 9990
| PubChem = 10419
| ChEMBL_Ref = {{ebicite|correct|EBI}}
| ChEMBL = 119108
| InChI = 1/C4H6/c1-3-4-2/h1-2H3
| InChIKey = XNMQEEKYCVKGBD-UHFFFAOYAO
| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| StdInChI = 1S/C4H6/c1-3-4-2/h1-2H3
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
| StdInChIKey = XNMQEEKYCVKGBD-UHFFFAOYSA-N
| CASNo_Ref = {{cascite|correct|CAS}}
| CASNo = 503-17-3
| UNII_Ref = {{fdacite|correct|FDA}}
| UNII = LKE6D3018E
| SMILES = CC#CC
}}
|Section2={{Chembox Properties
| C=4 | H=6
| Density = 0.691 g/mL
| MeltingPtC = -32
| BoilingPtC = 27
}}
}}
'''2-Butyne''' ('''dimethylacetylene''', '''crotonylene''' or '''but-2-yne''') is an [alkyne](/source/alkyne) with [chemical formula](/source/chemical_formula) CH3C≡CCH3. Produced artificially, it is a colorless, volatile, pungent liquid at [standard temperature and pressure](/source/standard_temperature_and_pressure).
2-Butyne is of interest to physical chemists because of its very low [torsional barrier](/source/torsional_barrier) and the problem of determining that barrier using high-resolution infrared spectroscopy. Analysis of its infrared spectrum[{{cite journal | last = di Lauro | first = C.|display-authors=etal| year = 1997 | title =The rotation-torsion structure in the ν11/ν15 (Gs) methyl rocking fundamental band in dimethylacetylene
| journal = J. Mol. Spectrosc.| volume = 184 | issue = 1
| pages = 177–185 | doi =10.1006/jmsp.1997.7321}}]
leads to a determination that the torsional barrier is only 6 cm−1 (1.2{{e|-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[{{cite journal | last1 = Longuet-Higgins | first1 = H.C. | year = 1963 | title = The symmetry groups of non-rigid molecules | journal = Molecular Physics | volume = 6 | issue = 5| pages = 445–460 | doi = 10.1080/00268976300100501 | bibcode = 1963MolPh...6..445L | doi-access = free }}][{{cite journal | author1=P. R. Bunker | year=1964
| title=The Rotation-Torsion Wavefunctions of Molecules that have two Identical Rotors
| journal=Mol. Phys. | volume=8 | page=81 | doi = 10.1080/00268976400100091}}] G36 shows that one would need to analyse its high resolution [rotation-vibration](/source/Rotational%E2%80%93vibrational_spectroscopy) [Raman spectrum](/source/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.[{{cite journal | last = Jacovella | first = Ugo|display-authors=etal| year = 2015
| title=Internal rotation, spin–orbit coupling, and low-frequency vibrations in the ground state of CH3–CC–CH+3 and CD3–CC–CD+3
| journal=Mol. Phys. | volume=113 | page=2115 | doi = 10.1080/00268976.2015.1005708| hdl=20.500.11850/182812| hdl-access=free}}]
2-Butyne (''dimethylethyne'') forms with [5-decyne](/source/5-decyne) (''dibutylethyne''), [4-octyne](/source/4-octyne) (''dipropylethyne'') and [3-hexyne](/source/3-hexyne) (''diethylethyne'') a group of symmetric alkynes.
==Synthesis==
2-Butyne can be synthesized by the [rearrangement reaction](/source/rearrangement_reaction) of [ethylacetylene](/source/ethylacetylene) in a solution of [ethanol](/source/ethanol)ic [potassium hydroxide](/source/potassium_hydroxide).[{{cite book|author1=Victor von Richter |author2=Hans Meerwein|title=Organic Chemistry: Chemistry of the aliphatic series Vol. I: Smith's 3rd American Ed.|year=1916|publisher=P. Blakiston's Sons & Co.|location=Philadelphia|page=89|url=https://books.google.com/books?id=UWlZAAAAYAAJ&q=dimethylacetylene+preparation&pg=PA89}}]
==Applications==
2-Butyne, along with [propyne](/source/propyne), is used to synthesize [alkylated](/source/alkylated) [hydroquinone](/source/hydroquinone)s in the [total synthesis](/source/total_synthesis) of [Vitamin E](/source/Vitamin_E).[{{cite journal|author1=Reppe, Walter |author2=Kutepow, N |author3=Magin, A |title=Cyclization of Acetylenic Compounds|journal=Angewandte Chemie International Edition in English|year=1969|volume=8|issue=10|pages=727–733|doi=10.1002/anie.196907271}}]
==See also==
*[Acetylenedicarboxylic acid](/source/Acetylenedicarboxylic_acid)
*[1-Butyne](/source/1-Butyne), a position isomer
*[1,4-Butynediol](/source/1%2C4-Butynediol)
*[Hexamethylbenzene](/source/Hexamethylbenzene), a product of 2-butyne [trimerization](/source/trimerization)
*[Hexafluoro-2-butyne](/source/Hexafluoro-2-butyne)
==References==
{{reflist}}
{{Alkynes}}
{{DEFAULTSORT:Butyne, 2-}}
Category:Alkynes
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Adapted from the Wikipedia article [2-Butyne](https://en.wikipedia.org/wiki/2-Butyne) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/2-Butyne?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.