Propyne

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Structural formula
Structure of propyne
General
Surname Propyne
other names
  • Methyl acetylene
  • Allylene
Molecular formula C 3 H 4
Brief description

colorless, almost odorless, narcotic gas

External identifiers / databases
CAS number 74-99-7
EC number 200-828-4
ECHA InfoCard 100,000,754
PubChem 6335
Wikidata Q151446
properties
Molar mass 40.06 g mol −1
Physical state

gaseous

density
  • 1.83 g l −1 (as gas, 0 ° C, 1013 hPa)
  • 1.707 g l −1 (as gas, 15 ° C)
  • 0.671 kg l −1 (as a liquid at the boiling point)
Melting point

−102.7 ° C

boiling point

−23.2 ° C

Vapor pressure
  • 512 k Pa (20 ° C)
  • 680 kPa (30 ° C)
  • 1150 kPa (50 ° C)
solubility
  • poorly soluble in water (3.3 g l −1 at 21 ° C)
Refractive index

1.3863 (−40 ° C)

safety instructions
GHS labeling of hazardous substances
02 - Highly / extremely flammable 04 - gas bottle

danger

H and P phrases H: 220-280
P: 210-377-381-403
MAK
  • not yet classified
  • Switzerland: 1000 ml m −3 or 1650 mg m −3
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions . Refractive index: Na-D line , 20 ° C

Propyne (methylacetylene) is an unsaturated , aliphatic hydrocarbon from the homologous series of alkynes with the empirical formula C 3 H 4 . It is a colorless, extremely flammable gas. Propyne is compressed during storage and transport and has to be stabilized.

Manufacturing

Propyne can be obtained by the dehydrohalogenation of dihalopropanes or 2-halopropenes. It can also by isomerization of Allen in the presence of bases. Technically, the gas is obtained from the C3 fraction of cracked gases by means of solvent extraction .

properties

Physical Properties

Propyne melts at −102.7 ° C and boils at −23.2 ° C. It has a characteristic smell. It's heavier than air. With a positive molar heat of formation of 183.4 kJ / mol, it is an endothermic compound. It is almost insoluble in water. It is readily soluble in alcohol.

According to Antoine, the vapor pressure function results from log 10 (P) = A− (B / (T + C)) (P in kPa, T in K) with A = 4.95219, B = 1226.123 and C = −1.926 in the temperature range from 161.5 K to 254.3 K or with A = 4.03069, B = 818.384 and C = −46.457 in the temperature range from 249.8 K to 398 K.

Important thermodynamic properties are listed in the following table:

property Type Value [unit]
Standard enthalpy of formation Δ f H 0 gas 183.4 kJ mol −1
Heat capacity c p 60.73 J mol −1 K −1 (25 ° C)
as a gas
Triple point T triple 168.5 K
Critical temperature T C 402.4 K
Critical pressure P C 56.3 bar
Critical volume V C 0.1635 l mol −1
Critical density ρ C 6.12 mol·l −1

Chemical properties

In particular, addition reactions take place at the very reactive triple bond . Like all terminal alkynes, propyne has weakly acidic properties.

Propyne

However, a dianion can also be generated with strong bases.

Reaction with alkyl halides results in 2-alkynes. For example, the reaction of propyne with methyl iodide gives 2-butyne ( dimethylacetylene ).

Propyne is in equilibrium with Propadiene :

H 3 C − C≡CH ⇌ H 2 C = C = CH 2

Safety-related parameters

Propyne forms highly flammable gas-air mixtures. The explosion range is between 1.8% by volume (38 g / m 3 ) as the lower explosion limit (LEL) and 16.8% by volume (280 g / m 3 ) as the upper explosion limit (UEL). The minimum ignition energy is 0.11 mJ. The limit gap width was determined to be 0.74 mm. This results in an assignment to explosion group IIB. The ignition temperature is 340 ° C. The substance therefore falls into temperature class T2. Analogous to acetylene , propyne, as an endothermic compound, tends to explode itself at higher temperatures and pressures.

use

Propyne can be used together with its isomer propadiene (Allen) as welding and cutting gas ( MAPP gas ). It is also an important intermediate in organic synthesis, e.g. B. for the production of vinyl compounds .

Individual evidence

  1. ^ Entry on Propin. In: Römpp Online . Georg Thieme Verlag, accessed on November 12, 2014.
  2. ↑ a b c d e f g h i j k Entry on propine in the GESTIS substance database of the IFA , accessed on March 13, 2018(JavaScript required) .
  3. ↑ Samuel H. Yalkowsky, Yan He, Parijat Jain: Handbook of Aqueous Solubility Data, Second Edition . CRC Press, 2016, ISBN 978-1-4398-0246-5 , pp. 47 ( limited preview in Google Book search).
  4. ↑ Hans-Dieter Jakubke, Ruth Karcher (coordinators): Lexicon of Chemistry in three volumes, Spektrum Verlag, Heidelberg, Volume 3, 1999, ISBN 3-8274-0381-2 , p. 105.
  5. ↑ David R. Lide (Ed.): CRC Handbook of Chemistry and Physics . 90th edition. (Internet version: 2010), CRC Press / Taylor and Francis, Boca Raton, FL, Physical Constants of Organic Compounds, pp. 3-446.
  6. ↑ Swiss Accident Insurance Fund (Suva): Limit values ​​- current MAK and BAT values (search for 74-99-7 or propyne ), accessed on November 2, 2015.
  7. ↑ a b G. B. Heisig, HM Davis: Physical Constants of Dimethylacetylene. In: J. Amer. Chem. Soc. 57, 1935, pp. 339-340. doi: 10.1021 / ja01305a031 .
  8. ↑ C. Friedel; L .: J. Liebigs Ann. Chem. 134 (1865) 263.
  9. ↑ JF Cordes, H. Günzler: Propyne / Propadiene rearrangement on activated carbon. In: Journal of Nature Research B . 15, 1960, p. 682 ( online ).
  10. ^ D. Sohns: Linde Reports Science and Technology. 30, 1979, p. 21.
  11. ↑ Linde AG: US 4 701 190 (1986), EP 0 224 748 (1986).
  12. ↑ a b D. D. Wagman, JE Kilpatrick, KS Pitzer, FD Rossini: Heats equilibrium constants, and free energies of formation of the acetylene hydrocarbons through the pentynes, to, 1,500 ° K. In: J. Res NBS.. 35, 1945, pp. 467-496.
  13. ^ WA van Hook: Vapor Pressures of the Methylacetylenes, H 3 CCCH, H 3 CCCD, D 3 CCCH, and D 3 CCCD. In: J. Chem. Phys. 46, 1967, pp. 1907-1918.
  14. ^ DR Stull: Vapor Pressure of Pure Substances - Organic Compounds. In: Ind. Eng. Chem. 39, 1947, pp. 517-540. doi: 10.1021 / ie50448a022 .
  15. ^ Selected Values ​​of Properties of Chemical Compounds. Thermodynamics Research Center, Texas A&M University, College Station, Texas, 1997.
  16. ^ O. Maass, CH Wright: Some physical properties of hydrocarbons containing two and three carbon atoms. In: J. Am. Chem. Soc. 43, 1921, pp. 1098-1111.
  17. ↑ a b c d C. Tsonopoulos, D. Ambrose: Vapor-Liquid Critical Properties of Elements and Compounds. 6. Unsaturated Aliphatic Hydrocarbons. In: J. Chem. Eng. Data. 41, 1996, pp. 645-656.
  18. ↑ KPC Vollhardt, NE Schore: Organic Chemistry. 4th edition. Wiley-VCH, 2007, ISBN 978-3-527-31380-8 , p. 41.
  19. ↑ BG RCI-Merkblatt T 033 Avoidance of ignition hazards due to electrostatic charges , Jedermann-Verlag, 2009, ISBN 978-3-86825-103-6 .
  20. ↑ E. Brandes, W. Möller: Safety-related parameters. Volume 1: Flammable Liquids and Gases. Wirtschaftsverlag NW - Verlag für neue Wissenschaft, Bremerhaven 2003.
  21. ^ F. Fitzgerald: Decomposition of Methyl Acetylene. In: Nature. 186, 1960, pp. 386-387. doi: 10.1038 / 186386a0 .

Web links

Wiktionary: Propin  - explanations of meanings, word origins, synonyms, translations