Vinylacetylene

Chemical compound From Wikipedia, the free encyclopedia

Vinylacetylene is the organic compound with the formula C4H4 or H2C=CH−C≡CH. The colourless gas was once used in the polymer industry. It is composed of both alkyne and alkene groups and is the simplest enyne.

Quick facts Names, Identifiers ...
Vinylacetylene
Names
Preferred IUPAC name
But-1-en-3-yne
Other names
  • Butenyne, normal isomer
  • 3-Butene-1-yne
  • Vinyl acetylene
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.010.650 Edit this at Wikidata
UNII
  • InChI=1S/C4H4/c1-3-4-2/h1,4H,2H2 checkY
    Key: WFYPICNXBKQZGB-UHFFFAOYSA-N checkY
  • InChI=1/C4H4/c1-3-4-2/h1,4H,2H2
    Key: WFYPICNXBKQZGB-UHFFFAOYAE
  • C#CC=C
Properties
H2C=CH−C≡CH
Molar mass 52.07456 g/mol
Appearance colourless gas
Boiling point 0 to 6 Â°C (32 to 43 Â°F; 273 to 279 K)
low
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
 Very flammable. Extremely dangerous because it can explode, even without air.
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g. chloroformFlammability 4: Will rapidly or completely vaporize at normal atmospheric pressure and temperature, or is readily dispersed in air and will burn readily. Flash point below 23 °C (73 °F). E.g. propaneInstability 3: Capable of detonation or explosive decomposition but requires a strong initiating source, must be heated under confinement before initiation, reacts explosively with water, or will detonate if severely shocked. E.g. hydrogen peroxideSpecial hazard W: Reacts with water in an unusual or dangerous manner. E.g. sodium, sulfuric acid
2
4
3
W
Flash point < −5 Â°C (23 Â°F; 268 K)
Except where otherwise noted, data are given for materials in their standard state (at 25 Â°C [77 Â°F], 100 kPa).
checkY verify (what is checkY☒N ?)
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Safety

Vinylacetylene is extremely dangerous because in high enough concentrations (typically > 30 mole percent, but pressure dependent) it can auto-detonate (explode without air being present) especially at elevated pressures, such as those seen in chemical plants processing C4 hydrocarbons (hydrocarbons with 4 carbon atoms).[2] An example of such an explosion occurred at a Union Carbide plant in Texas City in 1969.[3]

Synthesis

Vinylacetylene was first synthesized by Hofmann elimination of the related quaternary ammonium salt:[4]

[(CH3)3N+−CH2−CH=CH−CH2−N+(CH3)3](I−)2 → 2 [(CH3)3NH]+I− + H2C=CH−C≡CH

It is usually synthesized by dehydrohalogenation of 1,3-dichloro-2-butene Cl−CH2−CH=CCl−CH3.[5]

It also arises via the dimerization of acetylene, which is catalyzed by copper(I) chloride.[6]

Dehydrogenation of 1,3-butadiene is yet another route.[citation needed]

Application

At one time, chloroprene (2-chloro-1,3-butadiene), an industrially important monomer, was produced via the intermediacy of vinyl acetylene.[7] In this process, acetylene is dimerized to give vinyl acetylene, which is then combined with hydrogen chloride to give 4-chloro-1,2-butadiene via 1,4-addition. This allene derivative which, in the presence of cuprous chloride, rearranges to 2-chloro-1,3-butadiene:[8]

H2C=CH−C≡CH + HCl → H2ClC−CH=C=CH2
H2ClC−CH=C=CH2 → H2C=CH−CCl=CH2

References

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