| Methylacetylene | |
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Propyne |
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Other names
Methylacetylene |
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| Identifiers | |
| CAS number | 74-99-7 |
| ChEMBL | CHEMBL116902 |
| Jmol-3D images | Image 1 |
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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 |
| (verify) (what is: /?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) |
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| 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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Methyl acetylene exists in equilibrium with allene, the mixture of methyl acetylene and propadiene being called MAPD:
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.
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.)
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]
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