1,2-rearrangement

In a 1,2 shift the movement involves two adjacent atoms but moves over larger distances are possible.

The rearrangement is intramolecular and the starting compound and reaction product are structural isomers.

In an anionic transition state on the other hand 4 electrons are present thus antiaromatic and destabilized.

The first radical 1,2-rearrangement reported by Heinrich Otto Wieland in 1911[2] was the conversion of bis(triphenylmethyl)peroxide 1 to the tetraphenylethane 2.

[3] An example of a less common radical 1,2-shift can be found in the gas phase pyrolysis of certain polycyclic aromatic compounds.