The photolysis of aromatic diazides (DA) on a silica gel surface under
ambient air was studied. The main photolysis product is an insoluble
polymer residue containing the azo groups; its yield is 80 - 90% decom
posed DA. A mechanism was suggested that implies interaction between n
eighboring triplet nitrene molecules or between a nitrene and the azid
e group of a neighboring molecule to form the polymer as a principal r
eaction of nitrenes on the silica gel surface. The chain termination o
ccurs as a result of hydrogen abstraction by a triplet nitrene from th
e neighboring molecule to yield die primary amino groups. The DA photo
lysis is accompanied by the intramolecular rearrangement of DA molecul
ar fragments linking the benzene rings and by the formation of oxidati
on products: nitroso and azoxy compounds and nitroxyl radicals.