PHOTOCHEMICAL NITRATION BY TETRANITROMETHANE .22. ADDUCTS AS PRECURSORS OF NITRO SUBSTITUTION PRODUCTS FROM THE PHOTOLYSIS OF 1-METHOXYNAPHTHALENE-TETRANITROMETHANE, DEHYDRODIMER FORMATION AND THE REGIOCHEMISTRY OF TRINITROMETHANIDE ION ATTACK ON THE RADICAL-CATION OF 1-METHOXYNAPHTHALENE

The photolysis of 1-methoxynaphthalene with tetranitromethane in dichloromethane at 20 degrees C gives mainly 1-methoxy-4-nitronaphthalene (2) and 1-methoxy-4-trinitromethylnaphthalene (5), together with smaller amounts of 1-methoxy-2-nitronaphthalene (1) and the two adducts, 4-methoxy-r-1-nitro-t-2-trinitromethyl-1,2-dihydronaphthalene (6) and 4-methoxy-r-2-nitro-t-1-trinitromethyl-1,2-dihydronaphthalene (7). Photolysis in the presence of trifluoroacetic acid under otherwise identical conditions gives initially exclusively 4,4'-dimethoxy-1,1'-binaphthalene (10) as the product, trinitromethanide ion being eliminated as a reactant by protonation to give nitroform. EPR spectral and cyclic voltammetric data indicate that the radical cation 10(.+) is present in this reaction. Evidence is presented that, in the absence of trifluoroacetic acid, the reaction products 1, 2 and 5 all arise by decomposition of highly labile nitro-trinitromethyl or nitrito-trinitromethyl adducts 11, 12 and 14. The regiochemistry of attack of trinitromethanide ion on the radical cation of 1-methoxynaphthalene is discussed, and it is proposed that this step is reversible, the regiochemistry of attack being determined by the relative energies of the carbon radicals formed in the process. X-Ray crystal structures are reported for 1-methoxy-4-trinitromethylnaphthalene (5) and 4,4'-dimethoxy-1,1'-binaphthalene (10).