Propyne
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| Names | |
|---|---|
| IUPAC name
Prop-1-yne
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| Other names
Methylacetylene
Methyl acetylene Propyne | |
| Identifiers | |
3D model (JSmol)
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| ECHA InfoCard | 100.000.754 |
CompTox Dashboard (EPA)
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| Properties | |
| 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 [77 °F], 100 kPa).
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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.[1]
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.[1] 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 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 energy/volume ratio, 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.[2] Whereas purified propyne is expensive, MAPP gas can be used to cheaply generate large amounts of the reagent. [3]
References
- ^ 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. 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