Propyne

{{Short description|Alkyne hydrocarbon compound with three carbon atoms}} {{distinguish|propane|propene}} {{chembox | Verifiedfields = changed | verifiedrevid = 406858995 | Name = Propyne | ImageFile = PROPYNE.png | ImageSize = 120px | ImageName = Methylacetylene | ImageFile1 = Propyne-3D-vdW.png | ImageSize1 = 180px | PIN = Propyne<ref name=iupac2013>{{cite book | title = Nomenclature of Organic Chemistry. IUPAC Recommendations and Preferred Names 2013 (Blue Book) | chapter = Characteristic (Functional) and Substituent Groups | publisher = The Royal Society of Chemistry | date = 2014 | location = Cambridge | page = 374 | doi = 10.1039/9781849733069-00372 | isbn = 978-0-85404-182-4}}</ref><ref group="note">"Prop-1-yne" mistake fixed in the [https://www.qmul.ac.uk/sbcs/iupac/bibliog/BBerrors.html errata] {{Webarchive|url=https://web.archive.org/web/20190801093648/https://www.qmul.ac.uk/sbcs/iupac/bibliog/BBerrors.html |date=2019-08-01 }}. The locant is omitted according to P-14.3.4.2&nbsp;(d), p.&nbsp;31 for propene and P-31.1.1.1, Examples, p.&nbsp;374 for propyne.</ref> | SystematicName = | OtherNames = Methylacetylene<br />Methyl acetylene<br />Allylyne | IUPACName = | Section1 = {{Chembox Identifiers | CASNo = 74-99-7 | CASNo_Ref = {{cascite|correct|CAS}} | UNII_Ref = {{fdacite|correct|FDA}} | UNII = 086L40ET1B | ChEMBL_Ref = {{ebicite|changed|EBI}} | ChEMBL = 116902 | SMILES = CC#C | EINECS = 200-828-4 | PubChem = 6335 | ChemSpiderID = 6095 | InChI = 1/C3H4/c1-3-2/h1H,2H3 | InChIKey = MWWATHDPGQKSAR-UHFFFAOYAI | StdInChI = 1S/C3H4/c1-3-2/h1H,2H3 | StdInChIKey = MWWATHDPGQKSAR-UHFFFAOYSA-N | RTECS = | MeSHName = C022030 | ChEBI = 48086 | ChEBI_Ref = {{ebicite|correct|ebi}} | Beilstein = 878138 }} | Section2 = {{Chembox Properties | Formula = {{chem2|CH3C\tCH}} | MolarMass = 40.0639 g/mol | Density = 0.53 g/cm³ | MeltingPtC = -102.7 | BoilingPtC = -23.2 | Appearance = Colorless gas<ref name=NIOSH/> | Odor = Sweet<ref name=NIOSH/> | VaporPressure = 5.2 atm (20°C)<ref name=NIOSH/> }} | Section3 = {{Chembox Hazards | PEL = TWA 1000 ppm (1650 mg/m³)<ref name=NIOSH>{{PGCH|0392}}</ref> | ExploLimits = 1.7%-?<ref name=NIOSH/> | IDLH = 1700 ppm<ref name=NIOSH/> | REL = TWA 1000 ppm (1650 mg/m³)<ref name=NIOSH/> }} | Section4 = | Section5 = | Section6 = }}

'''Propyne''' ('''methylacetylene''') is an alkyne with the chemical formula {{chem2|CH3C\tCH}}. It is a component of MAPD gas—along with its isomer propadiene (allene), which was commonly used in gas welding. Unlike acetylene, propyne can be safely condensed.<ref name=Ullmann>Peter Pässler, Werner Hefner, Klaus Buckl, Helmut Meinass, Andreas Meiswinkel, Hans-Jürgen Wernicke, Günter Ebersberg, Richard Müller, Jürgen Bässler, Hartmut Behringer, Dieter Mayer, "Acetylene" in Ullmann's Encyclopedia of Industrial Chemistry Wiley-VCH, Weinheim 2007 ({{doi|10.1002/14356007.a01_097.pub2}}).</ref>

==Production and equilibrium with propadiene== Propyne exists in equilibrium with propadiene, the mixture of propyne and propadiene being called MAPD: :{{chem2|H3C\sC\tCH ⇌ H2C\dC\dCH2}} The coefficient of equilibrium ''K''_eq is 0.22 at 270&nbsp;°C or 0.1 at 5&nbsp;°C. MAPD is produced as a side product, often an undesirable one, by cracking propane to produce propene, an important feedstock in the chemical industry.<ref name=Ullmann/> MAPD interferes with the catalytic polymerization of propene.

===Laboratory methods=== Propyne can also be synthesized on laboratory scale by reducing 1-propanol,<ref>{{cite journal|author1=Keiser, Edward |author2=Breed, Mary |name-list-style=amp |title=The Action of Magnesium Upon the Vapors of the Alcohols and a New Method of Preparing Allylene|journal=Journal of the Franklin Institute|year=1895|volume=CXXXIX|issue=4 |pages=304–309|url=https://books.google.com/books?id=jn-VkwcIt5QC&q=allylene+franklin+magnesium&pg=PA309|access-date=20 February 2014|doi=10.1016/0016-0032(85)90206-6 |bibcode=1895FrInJ.139..304K }}</ref> allyl alcohol or acetone<ref>{{cite journal|last=Reiser, Edward II.|title=The preparation of Allylene, and the Action of Magnesium upon Organic Compounds|journal=The Chemical News and Journal of Industrial Science|year=1896|volume=LXXIV|pages=78–80|url=https://books.google.com/books?id=TxgAAAAAMAAJ&q=allylene+magnesium+preparing&pg=PA78|access-date=20 February 2014}}</ref> vapors over magnesium.

==Use as a rocket fuel== European space companies have researched using light hydrocarbons with liquid oxygen, a relatively high performing liquid rocket propellant combination that would also be less toxic than the commonly used MMH/NTO (monomethylhydrazine/nitrogen tetroxide). Their research showed{{citation needed|date=September 2013}} that propyne would be highly advantageous as a rocket fuel for craft intended for low Earth orbital operations. They reached this conclusion based upon a specific impulse expected to reach 370 s with oxygen as the oxidizer, a high density and power density—and the moderate boiling point, which makes the chemical easier to store than cryogenic fuels that must be kept at extremely low temperatures.<ref>{{Cite web |last1=Valentian |first1=Dominique |last2=Sippel |first2=Martin |last3=Grönland |first3=Tor-Arne |last4=Baker |first4=Adam |last5=van Den Meulen |first5=Jaap |last6=Fratacci |first6=Georges |last7=Caramelli |first7=Fabio |date=2004 |title=Green propellants options for launchers, manned capsules and interplanetary missions |url=http://www.la.dlr.de/ra/sart/publications/pdf/esa02-2004.pdf |url-status=dead |archive-url=https://web.archive.org/web/20060110171612/http://www.la.dlr.de/ra/sart/publications/pdf/esa02-2004.pdf |archive-date=2006-01-10 |website=la.dlr.de |publisher=DLR Lampoldshausen}}</ref>

==Organic chemistry== Propyne is a convenient three-carbon building block for organic synthesis. Deprotonation with ''n''-butyllithium gives propynyllithium. This nucleophilic reagent adds to carbonyl groups, producing alcohols and esters.<ref>{{OrgSynth | author1 = Michael J. Taschner|author2=Terry Rosen|author3=Clayton H. Heathcock | title = Ethyl Isocrotonate | collvol = 7 | collvolpages = 226| year = 1990 | prep = CV7P0226}}</ref> Whereas purified propyne is expensive, MAPP gas could be used to cheaply generate large amounts of the reagent.<ref>{{US patent reference | number = 5744071 | y = 1996 | m = 11 | d = 19 | inventor = Philip Franklin Sims, Anne Pautard-Cooper | title = Processes for preparing alkynyl ketones and precursors thereof }}</ref>

Propyne, along with 2-butyne, is also used to synthesize alkylated hydroquinones in the total synthesis of vitamin E.<ref name=Cyclization>{{cite journal|author1=Reppe, Walter |author2=Kutepow, N |author3=Magin, A |name-list-style=amp |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}}</ref>

The chemical shift of an alkynyl proton and propargylic proton generally occur in the same region of the ¹H NMR spectrum. In propyne, these two signals have almost exactly the same chemical shifts, leading to overlap of the signals, and the ¹H NMR spectrum of propyne, when recorded in deuteriochloroform on a 300&nbsp;MHz instrument, consists of a single signal, a sharp singlet resonating at 1.8 ppm.<ref>{{Cite book|title=Organic chemistry|first1=Marc|last1=Loudon|first2=Jim|last2=Parise|others=Parise, Jim, 1978-|isbn=9781936221349|edition= Sixth|location=Greenwood Village, Colorado|publisher=W. H. Freeman|oclc=907161629|date = 2015-08-26}}</ref>

== In astrophysics == Propyne has been detected in multiple astrophysical objects following its first observation in 1973 in the galactic center giant molecular cloud Sgr B2 using radio astronomy techniques.<ref>{{Cite journal |last1=Snyder |first1=L. E. |last2=Buhl |first2=D. |date=May 1973 |title=Interstellar Methylacetylene and Isocyanic Acid |url=https://www.nature.com/articles/physci243045a0 |journal=Nature Physical Science |language=en |volume=243 |issue=125 |pages=45–46 |doi=10.1038/physci243045a0 |bibcode=1973NPhS..243...45S |issn=2058-1106|url-access=subscription }}</ref> Propyne has been proposed to act as a precursor molecule to the formation of PAHs in space, such as indene.<ref>{{Cite journal |last1=Abplanalp |first1=Matthew J. |last2=Góbi |first2=Sándor |last3=Kaiser |first3=Ralf I. |date=2019-03-06 |title=On the formation and the isomer specific detection of methylacetylene (CH₃CCH), propene (CH₃CHCH₂), cyclopropane (c-C₃H₆), vinylacetylene (CH₂CHCCH), and 1,3-butadiene (CH₂CHCHCH₂) from interstellar methane ice analogues |url=https://pubs.rsc.org/en/content/articlelanding/2019/cp/c8cp03921f |journal=Physical Chemistry Chemical Physics |language=en |volume=21 |issue=10 |pages=5378–5393 |doi=10.1039/C8CP03921F |pmid=30221272 |bibcode=2019PCCP...21.5378A |issn=1463-9084|url-access=subscription }}</ref>

Propyne has been detected by infrared spectroscopy in the chemically reducing atmospheres of the outer planets in the Solar System, including on Jupiter in 2000 <ref>{{Citation |last1=Fouchet |first1=T. |title=Jupiter's hydrocarbons observed with ISO-SWS: vertical profiles of C₂H₆ and C₂H₂, detection of CH₃C2H |date=2000 |last2=Lellouch |first2=E. |last3=Bezard |first3=B. |last4=Feuchtgruber |first4=H. |last5=Drossart |first5=P. |last6=Encrenaz |first6=T.|arxiv=astro-ph/0002273 }}</ref> and on Saturn in 1997,<ref>{{Cite journal |last1=de Graauw |first1=T. |last2=Feuchtgruber |first2=H. |last3=Bezard |first3=B. |last4=Drossart |first4=P. |last5=Encrenaz |first5=T. |last6=Beintema |first6=D. A. |last7=Griffin |first7=M. |last8=Heras |first8=A. |last9=Kessler |first9=M. |last10=Leech |first10=K. |last11=Lellouch |first11=E. |last12=Morris |first12=P. |last13=Roelfsema |first13=P. R. |last14=Roos-Serote |first14=M. |last15=Salama |first15=A. |date=1997-05-01 |title=First results of ISO-SWS observations of Saturn: detection of CO₂, CH₃C₂H, C₄H₂ and tropospheric H₂O. |url=https://ui.adsabs.harvard.edu/abs/1997A&A...321L..13D/abstract |journal=Astronomy and Astrophysics |volume=321 |pages=L13–L16 |bibcode=1997A&A...321L..13D |issn=0004-6361}}</ref> both using the Infrared Space Observatory; on Titan in 1981 using Voyager's IRIS instrument;<ref>{{Cite journal |last1=Maguire |first1=W. C. |last2=Hanel |first2=R. A. |last3=Jennings |first3=D. E. |last4=Kunde |first4=V. G. |last5=Samuelson |first5=R. E. |date=August 1981 |title=C₃H₈ and C₃H₄ in Titan's atmosphere |url=https://www.nature.com/articles/292683a0 |journal=Nature |language=en |volume=292 |issue=5825 |pages=683–686 |doi=10.1038/292683a0 |bibcode=1981Natur.292..683M |issn=1476-4687|url-access=subscription }}</ref> and on the ice giants Uranus in 2006 <ref>{{Cite journal |last1=Burgdorf |first1=Martin |last2=Orton |first2=Glenn |last3=van Cleve |first3=Jeffrey |last4=Meadows |first4=Victoria |last5=Houck |first5=James |date=2006-10-01 |title=Detection of new hydrocarbons in Uranus' atmosphere by infrared spectroscopy |url=https://www.sciencedirect.com/science/article/abs/pii/S001910350600203X |journal=Icarus |volume=184 |issue=2 |pages=634–637 |doi=10.1016/j.icarus.2006.06.006 |bibcode=2006Icar..184..634B |issn=0019-1035|url-access=subscription }}</ref> and on Neptune in 2008 <ref>{{Cite journal |last1=Meadows |first1=Victoria S. |last2=Orton |first2=Glenn |last3=Line |first3=Michael |last4=Liang |first4=Mao-Chang |last5=Yung |first5=Yuk L. |last6=Van Cleve |first6=Jeffrey |last7=Burgdorf |first7=Martin J. |date=2008-10-01 |title=First Spitzer observations of Neptune: Detection of new hydrocarbons |url=https://linkinghub.elsevier.com/retrieve/pii/S0019103508002273 |journal=Icarus |volume=197 |issue=2 |pages=585–589 |doi=10.1016/j.icarus.2008.05.023 |bibcode=2008Icar..197..585M |issn=0019-1035|url-access=subscription }}</ref> using the Spitzer space telescope.

==Notes== <references group="note" />

==References== <references/>

==External links== * [http://webbook.nist.gov/cgi/cbook.cgi?ID=C74997 NIST Chemistry WebBook page for propyne] * [https://web.archive.org/web/20060110171612/http://www.la.dlr.de/ra/sart/publications/pdf/esa02-2004.pdf German Aerospace Center] * [https://web.archive.org/web/20070928144135/http://www.novachem.com/ProductServices/docs/CrudePropylene_MSDS_EN.pdf Nova Chemicals] * [https://www.cdc.gov/niosh/npg/npgd0392.html CDC - NIOSH Pocket Guide to Chemical Hazards] {{Alkynes}} {{Molecules detected in outer space}} {{Hydrides by group}}

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Category:Alkynes Category:Fuel gas Category:Rocket fuels