Photochemical reaction of 9-nitro-substituted anthracene-like molecules 9-methyl-10-nitroanthracene and 12-methyl-7-nitrobenz[a]anthracene

Photolysis of 9-methyl-10-nitroanthracene in chloroform or methanol produces mainly two products 9-methyl-9-nitrosoanthracen-10-one and 9,10-anthraquinone in about 4:1 ratio under ambient air. The formation of 9-methyl-9-nitrosoanthracen-10-one confirms the proposed excited state rearrangement reaction of the nitro group peri to two hydrogens and perpendicular to the aromatic rings. The nitro group rearranges to a nitrite, followed by breaking of the N–O bond producing NO radical. The NO radical further forms a bond with the carbon on the opposite site of the benzene ring through radical recombination. Photolysis of 12-methyl-7-nitrobenz[a]anthracene produced several nitroso ketone-like compounds which further convert to an aldehyde. Photolysis of the desmethyl nitro compounds, 9-nitroanthracene and 7-nitrobenz[a]anthracene, produced the respective quinones.