Isotoluene

The isotoluenes in organic chemistry are the non-aromatic toluene isomers with an exocyclic double bond.

[1][2] The three basic isotoluenes are ortho-isotoluene or 5-methylene-1,3-cyclohexadiene (here labelled 1); para-isotoluene (2); and meta-isotoluene (3).

The o- and p-isotoluenes isomerise to toluene, a reaction driven by aromatic stabilisation.

The intramolecular isomerisation, a 1,3-sigmatropic reaction, is unfavorable because an antarafacial mode is enforced.

Ortho-isotoluene has been researched in connection with the mechanism of initiator-free polymerization of polystyrene.