| Methylacetylene | |
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| IUPAC name |
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| Other names | Methylacetylene Methyl acetylene Propyne |
| Identifiers | |
| CAS number | [] |
| SMILES |
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| Properties | |
| Molecular formula | C3H4 |
| Molar mass | 40.0639 g/mol |
| Density | 0.53 g/cm³ |
| Melting point |
-102.7 °C, 170 K, -153 °F |
| Boiling point |
-23.2 °C, 250 K, -10 °F |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) | |
| Infobox references | |
Methylacetylene (propyne) is an alkyne with the chemical formula CH3C≡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]
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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]
External links
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". Org. Synth.; Coll. Vol. 7: 226.
- ^ US5,744,071 (1996-11-19) Philip Franklin Sims, Anne Pautard-Cooper, Processes for preparing alkynyl ketones and precursors thereof.
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