Propyne

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Propyne
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Names
Preferred IUPAC name
Other names
Methylacetylene
Methyl acetylene
Allylyne
Identifiers
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3D model (JSmol)
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878138
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MeSH C022030
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  • InChI=1S/C3H4/c1-3-2/h1H,2H3
    Key: MWWATHDPGQKSAR-UHFFFAOYSA-N
  • InChI=1/C3H4/c1-3-2/h1H,2H3
    Key: MWWATHDPGQKSAR-UHFFFAOYAI
  • CC#C
Properties
Page Module:Chem2/styles.css has no content.CH3C≡CH
Molar mass 40.0639 g/mol
Appearance Colorless gas[2]
Odor Sweet[2]
Density 0.53 g/cm3
Melting point −102.7 °C (−152.9 °F; 170.5 K)
Boiling point −23.2 °C (−9.8 °F; 250.0 K)
Vapor pressure 5.2 atm (20°C)[2]
Hazards
Explosive limits 1.7%-?[2]
NIOSH (US health exposure limits):
PEL (Permissible)
 TWA 1000 ppm (1650 mg/m3)[2]
REL (Recommended)
 TWA 1000 ppm (1650 mg/m3)[2]
IDLH (Immediate danger)
 1700 ppm[2]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Propyne (methylacetylene) is an alkyne with the chemical formula Page Module:Chem2/styles.css has no content.CH3C≡CH. 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.[3]

Production and equilibrium with propadiene

Propyne exists in equilibrium with propadiene, the mixture of propyne and propadiene being called MAPD:

Page Module:Chem2/styles.css has no content.H3C−C≡CH ⇌ H2C=C=CH2

The coefficient of equilibrium Keq is 0.22 at 270 °C or 0.1 at 5 °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.[3] MAPD interferes with the catalytic polymerization of propene.

Laboratory methods

Propyne can also be synthesized on laboratory scale by reducing 1-propanol,[4] allyl alcohol or acetone[5] 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] 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.[6]

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.[7] Whereas purified propyne is expensive, MAPP gas could be used to cheaply generate large amounts of the reagent.[8]

Propyne, along with 2-butyne, is also used to synthesize alkylated hydroquinones in the total synthesis of vitamin E.[9]

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 MHz instrument, consists of a single signal, a sharp singlet resonating at 1.8 ppm.[10]

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.[11] Propyne has been proposed to act as a precursor molecule to the formation of PAHs in space, such as indene.[12]

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 [13] and on Saturn in 1997,[14] both using the Infrared Space Observatory; on Titan in 1981 using Voyager's IRIS instrument;[15] and on the ice giants Uranus in 2006 [16] and on Neptune in 2008 [17] using the Spitzer space telescope.

Notes

  1. ^ "Prop-1-yne" mistake fixed in the errata Script error: No such module "webarchive".. The locant is omitted according to P-14.3.4.2 (d), p. 31 for propene and P-31.1.1.1, Examples, p. 374 for propyne.

References

  1. ^ Page Module:Citation/CS1/styles.css has no content."Characteristic (Functional) and Substituent Groups". Nomenclature of Organic Chemistry. IUPAC Recommendations and Preferred Names 2013 (Blue Book). Cambridge: The Royal Society of Chemistry. 2014. p. 374. doi:10.1039/9781849733069-00372. ISBN 978-0-85404-182-4.
  2. ^ a b c d e f g Page Module:Citation/CS1/styles.css has no content.NIOSH Pocket Guide to Chemical Hazards. "#0392". National Institute for Occupational Safety and Health (NIOSH).
  3. ^ a b 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 (Script error: No such module "CS1 identifiers".).
  4. ^ Page Module:Citation/CS1/styles.css has no content.Keiser, Edward & Breed, Mary (1895). "The Action of Magnesium Upon the Vapors of the Alcohols and a New Method of Preparing Allylene". Journal of the Franklin Institute. CXXXIX (4): 304–309. Bibcode:1895FrInJ.139..304K. doi:10.1016/0016-0032(85)90206-6. Retrieved 20 February 2014.
  5. ^ Page Module:Citation/CS1/styles.css has no content.Reiser, Edward II. (1896). "The preparation of Allylene, and the Action of Magnesium upon Organic Compounds". The Chemical News and Journal of Industrial Science. LXXIV: 78–80. Retrieved 20 February 2014.
  6. ^ Page Module:Citation/CS1/styles.css has no content.Valentian, Dominique; Sippel, Martin; Grönland, Tor-Arne; Baker, Adam; van Den Meulen, Jaap; Fratacci, Georges; Caramelli, Fabio (2004). "Green propellants options for launchers, manned capsules and interplanetary missions" (PDF). la.dlr.de. DLR Lampoldshausen. Archived from the original (PDF) on 2006-01-10.
  7. ^ Page Module:Citation/CS1/styles.css has no content.Michael J. Taschner; Terry Rosen; Clayton H. Heathcock (1990). "Ethyl Isocrotonate". Organic Syntheses; Page Module:Citation/CS1/styles.css has no content.Collected Volumes, vol. 7, p. 226.
  8. ^ Page Template:Citation/styles.css has no content.US patent 5744071, Philip Franklin Sims, Anne Pautard-Cooper, "Processes for preparing alkynyl ketones and precursors thereof", issued Script error: No such module "auto date formatter". 
  9. ^ Page Module:Citation/CS1/styles.css has no content.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.
  10. ^ Page Module:Citation/CS1/styles.css has no content.Loudon, Marc; Parise, Jim (2015-08-26). Organic chemistry. Parise, Jim, 1978- (Sixth ed.). Greenwood Village, Colorado: W. H. Freeman. ISBN 9781936221349. OCLC 907161629.
  11. ^ Page Module:Citation/CS1/styles.css has no content.Snyder, L. E.; Buhl, D. (May 1973). "Interstellar Methylacetylene and Isocyanic Acid". Nature Physical Science. 243 (125): 45–46. Bibcode:1973NPhS..243...45S. doi:10.1038/physci243045a0. ISSN 2058-1106.
  12. ^ Page Module:Citation/CS1/styles.css has no content.Abplanalp, Matthew J.; Góbi, Sándor; Kaiser, Ralf I. (2019-03-06). "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". Physical Chemistry Chemical Physics. 21 (10): 5378–5393. Bibcode:2019PCCP...21.5378A. doi:10.1039/C8CP03921F. ISSN 1463-9084. PMID 30221272.
  13. ^ Page Module:Citation/CS1/styles.css has no content.Fouchet, T.; Lellouch, E.; Bezard, B.; Feuchtgruber, H.; Drossart, P.; Encrenaz, T. (2000), Jupiter's hydrocarbons observed with ISO-SWS: vertical profiles of C2H6 and C2H2, detection of CH3C2H, arXiv:astro-ph/0002273
  14. ^ Page Module:Citation/CS1/styles.css has no content.de Graauw, T.; Feuchtgruber, H.; Bezard, B.; Drossart, P.; Encrenaz, T.; Beintema, D. A.; Griffin, M.; Heras, A.; Kessler, M.; Leech, K.; Lellouch, E.; Morris, P.; Roelfsema, P. R.; Roos-Serote, M.; Salama, A. (1997-05-01). "First results of ISO-SWS observations of Saturn: detection of CO2, CH3C2H, C4H2 and tropospheric H2O". Astronomy and Astrophysics. 321: L13–L16. Bibcode:1997A&A...321L..13D. ISSN 0004-6361.
  15. ^ Page Module:Citation/CS1/styles.css has no content.Maguire, W. C.; Hanel, R. A.; Jennings, D. E.; Kunde, V. G.; Samuelson, R. E. (August 1981). "C3H8 and C3H4 in Titan's atmosphere". Nature. 292 (5825): 683–686. Bibcode:1981Natur.292..683M. doi:10.1038/292683a0. ISSN 1476-4687.
  16. ^ Page Module:Citation/CS1/styles.css has no content.Burgdorf, Martin; Orton, Glenn; van Cleve, Jeffrey; Meadows, Victoria; Houck, James (2006-10-01). "Detection of new hydrocarbons in Uranus' atmosphere by infrared spectroscopy". Icarus. 184 (2): 634–637. Bibcode:2006Icar..184..634B. doi:10.1016/j.icarus.2006.06.006. ISSN 0019-1035.
  17. ^ Page Module:Citation/CS1/styles.css has no content.Meadows, Victoria S.; Orton, Glenn; Line, Michael; Liang, Mao-Chang; Yung, Yuk L.; Van Cleve, Jeffrey; Burgdorf, Martin J. (2008-10-01). "First Spitzer observations of Neptune: Detection of new hydrocarbons". Icarus. 197 (2): 585–589. Bibcode:2008Icar..197..585M. doi:10.1016/j.icarus.2008.05.023. ISSN 0019-1035.

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