Photochemical nitration by tetranitromethane. Part 36. Adduct formation in the photochemical reactions of 4-fluoroanisole and 4-fluoro-3-methylanisole

The photolysis of the charge transfer (CT) complex of tetranitromethane and 4-fluoroanisole 2 in dichloromethane at -20°C gives the epimeric 1-fluoro-4-methoxy-5-nitro-6-trinitromethylcyclohexa-1,3-dienes 8 and 9, the epimeric 1-fluoro-4-methoxy-3-nitro-6-trinitromethylcyclohexa-1,4-dienes 10 and 12, the epimeric 1-fluoro-4-methoxy-6-nitro-3-trinitromethylcyclohexa-1,4-dienes 11 and 13, a 1-fluoro-6-hydroxy-4-methoxy-3-trinitromethylcyclohexa-1,4-diene 14, together with 4-fluoro-2-trinitromethylanisole 3,4-fluoro-2-nitroanisole 4 and 3-fluoro-6-hydroxy-5-nitrobenzoic acid 15. In acetonitrile at 20 or -20°C, only minor amounts of adducts 13 and 14 are formed, together with aromatic compounds 3, 4 and 16. The photolysis of the CT complex of tetranitromethane and 4-fluoro-3-methylanisole 7 in dichloromethane at -20°C gives the epimeric 1-fluoro-4-methoxy-6-methyl-6-nitro-3-trinitromethylcyclo- hexa-1,4-dienes 23 and 24, 1-fluoro-4-methoxy-2-methyl-r-5-nitro-c-6- trinitromethylcyclohexa-1,3-diene 25 and predominantly 4-fluoro-5-methyl-2- trinitromethylanisole 19. In acetonitrile a similar reaction of 4-fluoro-3-methylanisole 7 gives only adduct 25, lesser amounts of the trinitromethyl compound 19 and increased amounts of 4-fluoro-5-methyl-2- nitroanisole 22. Photolysis reactions with tetranitromethane of either 2 or 7 in 1,1,1,3,3,3-hexafluoropropan-2-ol are slow and yield the nitroanisoles 4, or 20 and 22, respectively. X-Ray crystal structures are reported for 4-fluoro-5-methyl-2-trinitromethylanisole 19 and 4-fluoro-5-methyl-2- nitroanisole 22.