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Vinylacetylene

Chemical compound From Wikipedia, the free encyclopedia

Vinylacetylene

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
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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
UNII
  • InChI=1S/C4H4/c1-3-4-2/h1,4H,2H2 Y
    Key: WFYPICNXBKQZGB-UHFFFAOYSA-N Y
  • 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 °C (32 to 43 °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)
ThumbHealth 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 °C (23 °F; 268 K)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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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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