What is "benzvalene"

n. (context organic compound English) A highly reactive tricyclic unsaturated hydrocarbon, ''tricyclo[3.1-0.0^2,6]hex-3-ene'', that is a valence isomer of benzene

Benzvalene is an organic compound and one of several isomers of benzene. It was synthesised in 1971 by Thomas J. Katz et al.

The 1971 synthesis consisted of treating cyclopentadiene with methyllithium in dimethyl ether and then with dichloromethane and methyllithium in diethyl ether at −45 °C. The hydrocarbon in solution was described as having an extraordinary mephitic odor. Due to the high steric strain present in benzvalene, the pure compound easily detonates, for example by scratching.

The compound converts to benzene with a chemical half-life of approximately 10 days. This symmetry-forbidden transition is believed to take place through a diradical intermediate.