“…The benzidine rearrangement is usually carried out under 67 acid catalysis, but the purely thermal benzidine rearrangement is also known. These reactions 68 have been reviewed extensively [4,5,6] and will not be repeated here. A review on short-69 contact time, radical-forming gas-phase pyrolyses, which includes some hydrazine 70 derivatives, has been published [7].…”