Propyne

Propyne (methylacetylene) is an alkyne with the chemical formula CH
3C≡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.[1]

## Contents

* 1 Production and equilibrium with propadiene
* 1.1 Laboratory methods
* 2 Use as a rocket fuel
* 3 Organic chemistry
* 4 In Astrophysics
* 5 Notes
* 6 References
* 7 External links

## Production and equilibrium with propadiene

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

3C–C≡CH ⇌ H
2C=C=CH

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.[1] MAPD interferes with the catalytic polymerization of propene.

### Laboratory methods

Propyne can also be synthesized on laboratory scale by reducing 1-propanol,[2] allyl alcohol or acetone[3] 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 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.[4]

## 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.[5] Whereas purified propyne is expensive, MAPP gas could be used to cheaply generate large amounts of the reagent.[6]

Propyne, along with 2-butyne, is also used to synthesize alkylated hydroquinones in the total synthesis of vitamin E.[7]

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.[8]

## 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.[9] Propyne has been proposed to act as a precursor molecule to the formation of PAHs in space, such as indene.[10]

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 [11] and on Saturn in 1997,[12] both using the Infrared Space Observatory; on Titan in 1981 using Voyager's IRIS instrument;[13] and on the ice giants Uranus in 2006 [14] and on Neptune in 2008 [15] using the Spitzer space telescope.

## Notes

## References

1. ↑ 1.0 1.1 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).
2. ↑ 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. doi:10.1016/0016-0032(85)90206-6. Bibcode: 1895FrInJ.139..304K. https://books.google.com/books?id=jn-VkwcIt5QC&q=allylene+franklin+magnesium&pg=PA309. Retrieved 20 February 2014.
3. ↑ 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. https://books.google.com/books?id=TxgAAAAAMAAJ&q=allylene+magnesium+preparing&pg=PA78. Retrieved 20 February 2014.
4. ↑ 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". DLR Lampoldshausen. http://www.la.dlr.de/ra/sart/publications/pdf/esa02-2004.pdf.
5. ↑ Michael J. Taschner; Terry Rosen; Clayton H. Heathcock (1990). "Ethyl Isocrotonate". Organic Syntheses. http://www.orgsyn.org/demo.aspx?prep=CV7P0226. ;  Collective Volume, 7, pp. 226
6. ↑ US patent 5744071, Philip Franklin Sims, Anne Pautard-Cooper, "Processes for preparing alkynyl ketones and precursors thereof", issued 1996-11-19
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.
8. ↑ Loudon, Marc; Parise, Jim (2015-08-26). Organic chemistry. Parise, Jim, 1978- (Sixth ed.). Greenwood Village, Colorado: W. H. Freeman. ISBN 9781936221349. OCLC 907161629.
9. ↑ Snyder, L. E.; Buhl, D. (May 1973). "Interstellar Methylacetylene and Isocyanic Acid" (in en). Nature Physical Science 243 (125): 45–46. doi:10.1038/physci243045a0. ISSN 2058-1106. Bibcode: 1973NPhS..243...45S. https://www.nature.com/articles/physci243045a0.
10. ↑ 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" (in en). Physical Chemistry Chemical Physics 21 (10): 5378–5393. doi:10.1039/C8CP03921F. ISSN 1463-9084. PMID 30221272. Bibcode: 2019PCCP...21.5378A. https://pubs.rsc.org/en/content/articlelanding/2019/cp/c8cp03921f.
11. ↑ 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
12. ↑ de Graauw, T.; Feuchtgruber, H.; Bezard, B.; Drossart, P.; Encrenaz, T.; Beintema, D. A.; Griffin, M.; Heras, A. et al. (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. ISSN 0004-6361. Bibcode: 1997A&A...321L..13D. https://ui.adsabs.harvard.edu/abs/1997A&A...321L..13D/abstract.
13. ↑ Maguire, W. C.; Hanel, R. A.; Jennings, D. E.; Kunde, V. G.; Samuelson, R. E. (August 1981). "C3H8 and C3H4 in Titan's atmosphere" (in en). Nature 292 (5825): 683–686. doi:10.1038/292683a0. ISSN 1476-4687. Bibcode: 1981Natur.292..683M. https://www.nature.com/articles/292683a0.
14. ↑ 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. doi:10.1016/j.icarus.2006.06.006. ISSN 0019-1035. Bibcode: 2006Icar..184..634B. https://www.sciencedirect.com/science/article/abs/pii/S001910350600203X.
15. ↑ 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. doi:10.1016/j.icarus.2008.05.023. ISSN 0019-1035. Bibcode: 2008Icar..197..585M. https://linkinghub.elsevier.com/retrieve/pii/S0019103508002273.

## External links

* NIST Chemistry WebBook page for propyne
* German Aerospace Center
* Nova Chemicals
* CDC - NIOSH Pocket Guide to Chemical Hazards

* v
* t
* e

Alkynes

* Ethyne ( C2H2 )
* Propyne ( C3H4 )
* Butyne ( C4H6 )
* 1
* 2
* Pentyne ( C5H8 )
* 1
* 2
* Hexyne ( C6H10 )
* Heptyne ( C7H12 )
* Octyne ( C8H14 )
* 2
* 4
* Nonyne ( C9H16 )
* Decyne ( C10H18 )
* 1
* 5

Preparations|

* Cracking
* [[Chemistry:DehydrogenatDehydrogenation]] of alkane]], alkene
* Alkylation of alkynyl anion
* Dehydrohalogenation of dihaloalkane
* Fritsch–Buttenberg–Wiechell rearrangement
* Corey–Fuchs reaction
* Seyferth–Gilbert homologation

Reactions|

* Deprotonation
* Hydrogenation
* Halogenation
* Hydration
* Hydroboration
* Hydrohalogenation
* Thiol-yne reaction
* Alkyne trimerisation
* Diels–Alder reaction
* Pauson–Khand reaction
* Azide-alkyne Huisgen cycloaddition
* Sonogashira coupling
* Cadiot–Chodkiewicz coupling
* Glaser coupling
* Favorskii reaction

* v
* t
* e

Molecules detected in outer space

Molecules|

| Diatomic|

* Aluminium monochloride
* Aluminium monofluoride
* Aluminium monoxide
* Argonium
* Carbon monophosphide
* Carbon monosulfide
* Carbon monoxide
* Carborundum
* Cyanogen radical
* Diatomic carbon
* Fluoromethylidynium
* Helium hydride ion
* Hydrogen chloride
* Hydrogen fluoride
* Hydrogen (molecular)
* Hydroxyl radical
* Iron(II) oxide
* Magnesium monohydride cation
* Methylidyne radical
* Nitric oxide
* Nitrogen (molecular)
* Nitrogen monohydride
* Nitrogen sulfide
* Oxygen (molecular)
* Phosphorus monoxide
* Phosphorus mononitride
* Potassium chloride
* Silicon carbide
* Silicon mononitride
* Silicon monoxide
* Silicon monosulfide
* Sodium chloride
* Sodium iodide
* Sulfur monohydride
* Sulfur monoxide
* Titanium oxide

|
|

Triatomic|

* Aluminium hydroxide
* Aluminium isocyanide
* Amino radical
* Carbon dioxide
* Carbonyl sulfide
* CCP radical
* Chloronium
* Diazenylium
* Dicarbon monoxide
* Disilicon carbide
* Ethynyl radical
* Formyl radical
* Hydrogen cyanide (HCN)
* Hydrogen isocyanide (HNC)
* Hydrogen sulfide
* Hydroperoxyl
* Iron cyanide
* Isoformyl
* Magnesium cyanide
* Magnesium isocyanide
* Methylene radical
* N2H+
* Nitrous oxide
* Nitroxyl
* Ozone
* Phosphaethyne
* Potassium cyanide
* Protonated molecular hydrogen
* Sodium cyanide
* Sodium hydroxide
* Silicon carbonitride
* c-Silicon dicarbide
* SiNC
* Sulfur dioxide
* Thioformyl
* Thioxoethenylidene
* Titanium dioxide
* Tricarbon
* Water

Four
atoms|

* Acetylene
* Ammonia
* Cyanic acid
* Cyanoethynyl
* Cyclopropynylidyne
* Formaldehyde
* Fulminic acid
* HCCN
* Hydrogen peroxide
* Hydromagnesium isocyanide
* Isocyanic acid
* Isothiocyanic acid
* Ketenyl
* Methylene amidogen
* Methyl radical
* Propynylidyne
* Protonated carbon dioxide
* Protonated hydrogen cyanide
* Silicon tricarbide
* Thioformaldehyde
* Tricarbon monoxide
* Tricarbon sulfide
* Thiocyanic acid

Five
atoms|

* Ammonium ion
* Butadiynyl
* Carbodiimide
* Cyanamide
* Cyanoacetylene
* Cyanoformaldehyde
* Cyanomethyl
* Cyclopropenylidene
* Formic acid
* Isocyanoacetylene
* Ketene
* Methane
* Methoxy radical
* Methylenimine
* Propadienylidene
* Protonated formaldehyde
* Protonated formaldehyde
* Silane
* Silicon-carbide cluster

Six
atoms|

* Acetonitrile
* Cyanobutadiynyl radical
* E-Cyanomethanimine
* Cyclopropenone
* Diacetylene
* Ethylene
* Formamide
* HC4N
* Ketenimine
* Methanethiol
* Methanol
* Methyl isocyanide
* Pentynylidyne
* Propynal
* Protonated cyanoacetylene

Seven
atoms|

* Acetaldehyde
* Acrylonitrile
* Vinyl cyanide
* Cyanodiacetylene
* Ethylene oxide
* Glycolonitrile
* Hexatriynyl radical
* Methylacetylene
* Methylamine
* Methyl isocyanate
* Vinyl alcohol

Eight
atoms|

* Acetic acid
* Aminoacetonitrile
* Cyanoallene
* Ethanimine
* Glycolaldehyde
* Heptatrienyl radical
* Hexapentaenylidene
* Methylcyanoacetylene
* Methyl formate
* Propenal

Nine
atoms|

* Acetamide
* Cyanohexatriyne
* Cyanotriacetylene
* Dimethyl ether
* Ethanol
* Methyldiacetylene
* Octatetraynyl radical
* Propene
* Propionitrile

Ten
atoms
or more|

* Acetone
* Benzene
* Benzonitrile
* Buckminsterfullerene (C60, C60+, fullerene, buckyball)
* C70 fullerene
* Cyanodecapentayne
* Cyanopentaacetylene
* Cyanotetra-acetylene
* Ethylene glycol
* Ethyl formate
* Methyl acetate
* Methyl-cyano-diacetylene
* Methyltriacetylene
* Propanal
* n-Propyl cyanide
* Pyrimidine

Deuterated
molecules|

* Ammonia
* Ammonium ion
* Formaldehyde
* Formyl radical
* Heavy water
* Hydrogen cyanide
* Hydrogen deuteride
* Hydrogen isocyanide
* Methylacetylene
* N2D+
* Trihydrogen cation

Unconfirmed|

* Anthracene
* Dihydroxyacetone
* Ethyl methyl ether
* Glycine
* Graphene
* H2NCO+
* Linear C5
* Naphthalene cation
* Phosphine
* Pyrene
* Silylidine

Related|

* Abiogenesis
* Astrobiology
* Astrochemistry
* Atomic and molecular astrophysics
* Chemical formula
* Circumstellar envelope
* Cosmic dust
* Cosmic ray
* Cosmochemistry
* Diffuse interstellar band
* Earliest known life forms
* Extraterrestrial life
* Extraterrestrial liquid water
* Forbidden mechanism
* Homochirality
* Intergalactic dust
* Interplanetary medium
* Interstellar medium
* Photodissociation region
* Iron–sulfur world theory
* Kerogen
* Molecules in stars
* Nexus for Exoplanet System Science
* Organic compound
* Outer space
* PAH world hypothesis
* Panspermia
* Polycyclic aromatic hydrocarbon (PAH)
* RNA world hypothesis
* Spectroscopy
* Tholin

* Category:Astrochemistry
*   *   *

* v
* t
* e

Binary compounds of hydrogen

Alkali metal (Group 1) hydrides|

* LiH
* NaH
* KH
* RbH
* CsH

Lithium hydride, LiH
ionic metal hydride

Beryllium hydride
Left (gas phase): BeH2
covalent metal hydride
Right: (BeH2)n (solid phase)
polymeric metal hydride

Borane and diborane
Left: BH3 (special conditions), covalent metalloid hydride
Right: B2H6 (standard conditions), dimeric metalloid hydride

Methane, CH4
covalent nonmetal hydride

Ammonia, NH3
covalent nonmetal hydride

Water, H2O
covalent nonmetal hydride

Hydrogen fluoride, HF
covalent nonmetal hydride

Alkaline (Group 2) earth hydrides|

| Monohydrides|

* BeH
* MgH
* CaH
* SrH
* BaH

|

Dihydrides|

* BeH2
* MgH2
* CaH2
* SrH2
* BaH2

|

Group 13 hydrides|

| Boranes|

* BH3
* B2H6
* B2H2
* B2H4
* B4H10
* B5H9
* B5H11
* B6H10
* B6H12
* B10H14
* B18H22

|

Alanes|

* AlH3
* Al2H6

|

Gallanes|

* GaH3
* Ga2H6

|

Indiganes|

* InH3
* In2H6

|

Thallanes|

* TlH3
* Tl2H6

|

Group 14 hydrides|

| Linear alkanes|

* CH4
* C2H6
* C3H8
* C4H10
* C5H12
* C6H14
* C7H16
* C8H18
* C9H20
* C10H22
* more...

|

Linear alkenes|

* C2H4
* C3H6
* C4H8
* C5H10
* C6H12
* C7H14
* C8H16
* C9H18
* C10H20
* more...

|

Linear alkynes|

* C2H2
* C3H4
* C4H6
* C5H8
* C6H10
* C7H12
* C8H14
* C9H16
* C10H18
* more...

|

Silanes|

* SiH4
* Si2H6
* Si3H8
* Si4H10
* Si5H12
* Si6H14
* Si7H16
* Si8H18
* Si9H20
* Si10H22
* more...

|

Silenes|

* Si2H4

|

Silynes|

* Si2H2
* SiH

|

Germanes|

* GeH4
* Ge2H6
* Ge3H8
* Ge4H10
* Ge5H12

|

Stannanes|

* SnH4
* Sn2H6

|

Plumbanes|

* PbH4

|

* CH
* CH2
* CH3
* C2H
* Cycloalkanes
* Cycloalkenes
* Annulenes
* Many more

Pnictogen (Group 15) hydrides|

| Azanes|

* NH3
* N2H4
* N3H5
* N4H6
* N5H7
* N6H8
* N7H9
* N8H10
* N9H11
* N10H12
* more...

|

Azenes|

* N2H2
* N3H3
* N4H4

|

Phosphanes|

* PH3
* P2H4
* P3H5
* P4H6
* P5H7
* P6H8
* P7H9
* P8H10
* P9H11
* P10H12
* more...

|

Phosphenes|

* P2H2
* P3H3
* P4H4

|

Arsanes|

* AsH3
* As2H4

|

Stibanes|

* SbH3

|

Bismuthanes|

* BiH3

|

* HN3
* NH
* radical

Hydrogen chalcogenides (Group 16 hydrides)|

| Polyoxidanes|

* H2O
* H2O2
* H2O3
* H2O4
* H2O5
* H2O6
* H2O7
* H2O8
* H2O9
* H2O10
* more...

|

Polysulfanes|

* H2S
* H2S2
* H2S3
* H2S4
* H2S5
* H2S6
* H2S7
* H2S8
* H2S9
* H2S10
* more...

|

Selanes|

* H2Se
* H2Se2

|

Tellanes|

* H2Te
* H2Te2

|

Polanes|

* PoH2

|

* HO
* HO2
* HO3
* H2O+–O–
* H2S=S
* (HS)2S+–S–
* HS
* HDO
* D2O
* T2O

Hydrogen halides (Group 17 hydrides)|

* HF
* HCl
* HBr
* HI
* HAt

Transition metal hydrides|

* ScH2
* YH2
* YH3
* TiH2
* ZrH2
* HfH2
* VH
* VH2
* NbH
* NbH2
* TaH
* CrH
* CrH2
* CrHx
* NiH
* PdHx (x < 1)
* FeH
* FeH2
* FeH5
* CuH
* ZnH2
* CdH2
* HgH2

Lanthanide hydrides|

* LaH2
* LaH3
* LaH10
* CeH2
* CeH3
* PrH2
* PrH3
* NdH2
* NdH3
* SmH2
* SmH3
* EuH2
* GdH2
* GdH3
* TbH2
* TbH3
* DyH2
* DyH3
* HoH2
* HoH3
* ErH2
* ErH3
* TmH2
* TmH3
* YbH2
* YbH2.5
* LuH2
* LuH3

Actinide hydrides|

* AcH2
* ThH2
* Th4H15
* PaH3
* UH3
* NpH2
* NpH3
* PuH2
* PuH3
* AmH2
* AmH3
* CmH2

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