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| Names | |
|---|---|
| IUPAC name Propyne | |
| Other names
Methylacetylene Methyl acetylene | |
| Identifiers | |
| CAS Number | |
| 3D model (JSmol) | |
| ECHA InfoCard | 100.000.754 
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| CompTox Dashboard (EPA) | |
SMILES
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| Properties | |
| Chemical formula | C3H4 |
| Molar mass | 40.0639 g/mol |
| 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) |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C , 100 kPa).
 Y verify (what is ?)
Infobox references
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Methylacetylene (propyne) is an alkyne with the chemical formula Template:CarbonH3C≡CH. It is a component of MAPP gas along with its isomer 1,2-propadiene (allene), which is commonly used in gas welding. Unlike acetylene, methylacetylene can be safely condensed.
Production and equilibrium with allene
Methylacetylene exists in equilibrium with allene, the mixture of methylacetylene and propadiene being called MAPD:
- H3CC≡CH ⇌ H2C=C=CH2
Keq = 0.22 (270 °C), 0.1 K (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. MAPD interferes with the catalytic polymerization of propene.
Use as a rocket fuel
Research by European space concerns into using light hydrocarbons with liquid oxygen as a relatively high performing liquid rocket propellant combination which would also be less toxic than the commonly used MMH/NTO (monomethylhydrazine/nitrogen tetroxide) systems, showed that propyne would be highly advantageous as a rocket fuel for craft intended for low Earth orbital operations. This conclusion was reached based upon a specific impulse expected to reach 370 s if oxygen is used as oxidizer, a high density and power density, and the moderate boiling point, which causes the chemical to present fewer problems in storage than for example a fuel that needs to be kept at extremely low temperatures. (See cryogenics.)
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. Whereas purified propyne is expensive, MAPP gas can be used to cheaply generate large amounts of the reagent.
External links
References
- ^ 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. 10.1002/14356007.a01 097.pub2
- Michael J. Taschner, Terry Rosen, and Clayton H. Heathcock (1990). "Ethyl Isocrotonate". Organic Syntheses
{{cite journal}}: CS1 maint: multiple names: authors list (link); Collected Volumes, 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
| Alkynes | |
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| Preparations | |
| Reactions | |