Vinylacetylene

Vinylacetylene is the organic compound with the formula C₄H₄. The colourless gas was once used in the polymer industry. It is composed of both alkyne and alkene groups.

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. An example of such an explosion occurred at a Union Carbide plant in Texas City in 1969.