Propadien

Structural formula
General
Surname	Propadien
other names	Everyone; Dimethylene methane; Propa-1,2-diene;
Molecular formula	C 3 H 4
Brief description	colorless gas
External identifiers / databases
EC number	207-335-3
ECHA InfoCard	100.006.670
PubChem	10037
Wikidata	Q422942
properties
Molar mass	40.06 g mol −1
Physical state	gaseous
Melting point	−136 ° C
boiling point	−34 ° C
Vapor pressure	0.91 M Pa (21 ° C)
solubility	almost insoluble in water
safety instructions
H and P phrases	H: 220-280
	P: 210-377-381-410 + 403
Thermodynamic properties
ΔH f 0	190.5 kJ / mol
	As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Propadiene [ … diˈeːn ] is the 1,2- diene of propane and thus the parent compound of the allenes . The common name of the connection is therefore "Allen" . It has the molecular formula C ₃ H ₄ . The terminal CH ₂ groups are in one plane with the middle C atom, but are rotated by 90 ° with respect to one another. Chemical compounds in which one or more hydrogen atoms of propadiene have been exchanged for other radicals can be chiral ( axial chirality ).

Extraction and presentation

The preparation succeeds in good yields in a synthesis sequence starting from allyl bromide , which is first converted to 1,2,3-tribromopropane by bromine addition. Subsequent dehydrohalogenation to 2,3-dibromopropene and reduction using zinc powder gives the propadiene.

properties

In propadiene, the middle carbon atom is sp-hybridized, the two outer carbon atoms are sp ² - hybridized . One speaks here of cumulative double bonds .

Although propadiene, like its related propene, has double bonds, it does not display the typical chemical and physical properties of alkenes . For example, in the presence of basic catalysts, isomerization to propyne takes place .

H ₂ C = C = CH ₂ ⇌ H ₃ C − C≡CH

use

Propadiene is used in a mixture with propyne as welding and cutting gas ( MAPP gas ). In organic synthesis, it is used as a raw material in the manufacture of insecticides .

Web links

Commons : Allene - collection of images, videos and audio files

Individual evidence

↑ ^a ^b ^c ^d entry on all. In: Römpp Online . Georg Thieme Verlag, accessed on September 29, 2014.
↑ ^a ^b ^c Allene data sheet at Sigma-Aldrich , accessed on April 22, 2011 ( PDF ).

↑ ^a ^b Entry on all in the GESTIS substance database of the IFA , accessed on January 9, 2019(JavaScript required) .

↑ David R. Lide (Ed.): CRC Handbook of Chemistry and Physics . 90th edition. (Internet version: 2010), CRC Press / Taylor and Francis, Boca Raton, FL, Standard Thermodynamic Properties of Chemical Substances, pp. 5-23.

↑ Hauptmann / Graefe / Remane: Textbook of Organic Chemistry , Deutscher Verlag der Grundstoffindustrie, Leipzig, 1980, p. 230.

^ Norbert Krause (editor), A. Stephen K. Hashmi (editor): Modern Allene Chemistry , Wiley-VCH Verlag, 2004. ISBN 978-3-527-30671-8 .

[roempp-1] try on all. In: Römpp Online . Georg Thieme Verlag, accessed on September 29, 2014.

[Sigma-2] Allene data sheet at Sigma-Aldrich , accessed on April 22, 2011 ( PDF ).

[GESTIS-3] Entry on all in the GESTIS substance database of the IFA , accessed on January 9, 2019(JavaScript required) .

[CRC90_5_23-4] David R. Lide (Ed.): CRC Handbook of Chemistry and Physics . 90th edition. (Internet version: 2010), CRC Press / Taylor and Francis, Boca Raton, FL, Standard Thermodynamic Properties of Chemical Substances, pp. 5-23.

[5] Hauptmann / Graefe / Remane: Textbook of Organic Chemistry , Deutscher Verlag der Grundstoffindustrie, Leipzig, 1980, p. 230.

[Krause-6] Norbert Krause (editor), A. Stephen K. Hashmi (editor): Modern Allene Chemistry , Wiley-VCH Verlag, 2004. ISBN 978-3-527-30671-8 .