Propyne
 |
|
 |
|
| Names | |
|---|---|
| IUPAC name
Propyne
|
|
| Other names
Methylacetylene
Methyl acetylene Allylene |
|
| Identifiers | |
74-99-7  |
|
| ChEBI | CHEBI:48086 |
| ChEMBL | ChEMBL116902  |
| ChemSpider | 6095 |
| EC Number | 200-828-4 |
|
|
| Jmol interactive 3D | Image |
| MeSH | C022030 |
| PubChem | 6335 |
|
|
| Properties | |
| C3H4 | |
| Molar mass | 40.0639 g/mol |
| Appearance | Colorless gas[1] |
| Odor | Sweet[1] |
| 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)[1] |
| Hazards | |
| Explosive limits | 1.7%-?[1] |
| US health exposure limits (NIOSH): | |
|
PEL (Permissible)
|
TWA 1000 ppm (1650 mg/m3)[1] |
|
REL (Recommended)
|
TWA 1000 ppm (1650 mg/m3)[1] |
|
IDLH (Immediate danger
|
1700 ppm[1] |
|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
|
|
 verify (what is ?) |
|
| Infobox references | |
Propyne (methylacetylene) is an alkyne with the chemical formula CH3C≡CH. It was a component of MAPP gas—along with its isomer propadiene (allene), which was commonly used in gas welding. Unlike acetylene, propyne can be safely condensed.[2]
Contents
Production and equilibrium with propadiene[edit]
Propyne exists in equilibrium with propadiene, the mixture of propyne and propadiene being called MAPD:
- H3CC≡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.[2] MAPD interferes with the catalytic polymerization of propene.
Laboratory Methods[edit]
Propyne can also be synthesized on laboratory scale by reducing 1-propanol,[3] allyl alcohol or acetone[4] vapors over magnesium.
Use as a rocket fuel[edit]
European space companies have researched using light hydrocarbons with liquid oxygen as 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 fuels that must be kept at extremely low temperatures. (See cryogenics.)
Organic chemistry[edit]
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]
References[edit]
- ^ a b c d e f g "NIOSH Pocket Guide to Chemical Hazards #0392". National Institute for Occupational Safety and Health (NIOSH).
- ^ a b Peter Pässler, Werner Hefner, Klaus Buckl, Helmut Meinass, Andreas Meiswinkel, Hans-Jũrgen 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).
- ^ Keiser, Edward; & Breed, Mary (1895). "The Action of Magnesium Upon the Vapors of the Alcohols and a New Method of Preparing Allylene". The Journal of the Franklin Institute. CXXXIX: 304–309. doi:10.1016/0016-0032(85)90206-6. Retrieved 20 February 2014.
- ^ 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.
- ^ Michael J. Taschner, Terry Rosen, and Clayton H. Heathcock (1990). "Ethyl Isocrotonate". Org. Synth.; Coll. Vol. 7, p. 226
- ^ US patent 5744071, Philip Franklin Sims, Anne Pautard-Cooper, "Processes for preparing alkynyl ketones and precursors thereof", issued 1996-11-19
- ^ Reppe, Walter; Kutepow, N; and Magin, A (1969). "Cyclization of Acetylenic Compounds". Angewandte Chemie International Edition in English 8 (10): 727–733. doi:10.1002/anie.196907271. Retrieved 26 December 2013.
External links[edit]
- NIST Chemistry WebBook page for propyne
- German Aerospace Center
- Nova Chemicals
- CDC - NIOSH Pocket Guide to Chemical Hazards
|
|
||||||
|
