Propyne
- Methylacetylene
- Allylene
Colorless, almost odorless, acting anesthetic gas
Gaseous
1.83 g · l-1 (0 ° C, 1013 hPa)
-102.7 ° C
-23.2 ° C
512 kPa ( 20 ° C)
Very poor in water ( 3.07 g · l -1)
1.3863 (-40 ° C)
Risk
Not yet classified
Template: Infobox chemical / molecular formula search available
Propyne ( methylacetylene ) is an unsaturated aliphatic hydrocarbon is selected from the homologous series of alkynes with the formula C3H4. It is a colorless, highly flammable gas. During storage and transportation propyne is compressed, it has to be stabilized.
Production
Propyne can be obtained by dehydrohalogenation of Dihalogenpropanen or 2 halopropenes. It can also be prepared by isomerization of all in the presence of bases. Technically, the gas from the C3 fraction of cracked gases is recovered by solvent extraction.
Properties
Physical Properties
Propyne melts at -102.7 ° C and boils at -23.2 ° C. It has a characteristic odor. It is heavier than air. With a positive molar heat of formation of 183.4 kJ / mol is an endothermic compound. In water, it is virtually insoluble. In alcohols, it is readily soluble.
The vapor pressure function is given by Antoine corresponding log10 (P) = A- ( B / ( T C)) (P in kPa, T in K) with A = 4.95219, B = 1226.123 and C = -1.926 in temperature range of 161.5 to 254.3 K and K A = 4.03069 B = 818.384, and C = -46457 in the temperature range of 249.8 K to 398 K.
Important thermodynamic properties are listed in the following table:
Chemical Properties
At the very reactive triple bond addition reactions mainly take place. Like all terminal alkynes propyne has weakly acidic properties.
With strong bases, however, a dianion is generated.
By reaction with alkyl halides to give 2- alkynes. Is obtained by the reaction of propyne with methyl 2-butyne ( dimethylacetylene ).
Safety characteristics
Propyne forms flammable gas - air mixtures. The explosion range is between 1.8 vol % (30 g/m3) as the lower explosive limit ( LEL) and 16.8 % by volume (280 g/m3 ) and upper explosive limit (UEL ). The minimum is 0.11 mJ. The marginal gap width was determined to be 0.74 mm. The result is thus a mapping in the explosion group IIB. The ignition temperature is 340 ° C. The fabric falls within the temperature class T2. Analogously to the acetylene tends propyne as endothermic compound to explosive spontaneous decomposition at higher temperatures and pressures.
Use
Propyne can be used together with its isomer Allen as welding and cutting gas. It is furthermore an important intermediate in organic synthesis, for example, for the production of vinyl compounds.