Propadiene is the simplest allen , an organic compound with a cumulated double bond (C = C). The first compound of a number of allens . The terminal CH 2 groups lie in the same plane with the central carbon atom, but are rotated 90 ° relative to each other [1] . Included in welding mixtures. In its pure form it is used for some special types of welding . In organic synthesis, it is used as a raw material for the production of insecticides [2] .
| Propadiene | |
|---|---|
 | |
 | |
 | |
| General | |
| Systematic name | 1,2-propadiene |
| Abbreviations | colorless gas |
| Traditional names | Dimethylene methane Allen |
| Chem. formula | C 3 H 4 |
| Physical properties | |
| Molar mass | 40.031300128 g / mol |
| Density | 0.546 g / cm³ |
| Thermal properties | |
| T. melt. | −136 ° C |
| T. bale. | −34 ° C |
| Etc. blast | 13 % |
| Enthalpy of Education | 190.5 kJ / mol |
| Steam pressure | 6.605 atm |
| Classification | |
| Reg. CAS number | 463-49-0 |
| PubChem | |
| Reg. EINECS number | 207-335-3 |
| Smiles | |
| Inchi | |
| Reg. EC number | 207-335-3 |
| Chebi | 37601 |
| UN number | 2200 |
| ChemSpider | |
| Security | |
| R phrases | R12 |
| S-phrases | S9 , S16 , S33 |
| GHS icons |  |
| NFPA 704 |  four 0 3 |
Production
Production goes with a good exit. The synthesis begins with allyl bromide , which is first converted by the addition of bromine to 1,2,3-tribromopropane. The removal of hydrobromic acid with the formation of 2,3-dibromopropene, and its subsequent reduction with zinc powder gives propadiene [3] .
Equilibrium with methylacetylene
Propadiene always exists in equilibrium with methylacetylene . This mixture is sometimes called MAPD by the first letters m- methyl, a- acetylene, p- prop and d - diene:
For this reaction, K eq = 0.22 (270 ° C) at 0.1 K (5 ° C).
MAPDs are produced as a by-product, usually undesirable, by cracking propane to produce propene , an important starting material for many chemical plants. MAPD can interact in a Ziegler – Natta catalyst , interfering with polymerization of propene [4] .
Notes
- ↑ IUPAC Gold Book internet edition: " allenes ".
- ↑ Eintrag zu Allen (German) . In: Römpp Online . Georg Thieme Verlag, abgerufen am 29. September 2014.
- ↑ Hauptmann / Graefe / Remane "Lehrbuch der Organischen Chemie", Deutscher Verlag der Grundstoffindustrie Leipzig 1980, S. 230.
- ↑ Klaus Buckl, Andreas Meiswinkel “Propyne” in Ullmann's Encyclopedia of Industrial Chemistry 2008, Wiley-VCH, Weinheim. DOI : 10.1002 / 14356007.m22_m01