PHOTOCHEMICAL NITRATION BY TETRANITROMETHANE .29. ADDUCT FORMATION INTHE PHOTOCHEMICAL-REACTION OF TETRANITROMETHANE AND 1,5-DIMETHYLNAPHTHALENE - ALLYLIC REARRANGEMENTS OF ADDUCTS

Photolysis of the 1,5-dimethylnaphthalene/tetranitromethane charge-tra nsfer complex yields the triad of 1,5-dimethylnaphthalene radical cati on, nitrogen dioxide and trinitromethanide ion. Recombination of this triad gives predominantly the epimeric l-1-nitro-4-trinitromethyl-1,4- dihydronaphthalenes (18) and (27), the epimeric l-1-nitro-4-trinitrome thyl-1,4-dihydronaphthalenes (20) and (21), -1-nitro-t-2-trinitromethy l-1,2-dihydronaphthalene (19), -dimethyl-t-2-trinitromethyl-1,2-dihydr onaphthalen -r-1-ol (23), nitro cycloadduct (22), hydroxy cycloadduct (24), nitronic ester (25) and 4,8-dimethyl-1-nitronaphthalene (26). Ad duct (19) is formed substantially by allylic rearrangement of yl-1-nit ro-4-trinitromethyl-1,4-dihydronaphthalene (18), and adduct (23) and i ndirectly nitronic ester (25) by allylic rearrangement of a postulated intermediate l-t-4-trinitromethyl-1,4-dihydronaphthalen-r-1-ol. (32). Adducts (18), (19), (23), (25) and (27) are formed by attack of trini tromethanide ion at C1 of the 1,5-dimethylnaphthalene radical cation, while adducts (20)-(22) and (24) are formed by the corresponding attac k at C4, the reaction pathways being determined by the relative energi es of the intermediate delocalized carbon radicals. Adduct formation i s substantially suppressed for a photolysis when trifluoroacetic acid (0.7 M) is added to the dichloromethane solvent at 20 degrees, 1,5-dim ethyl-4-nitronaphthalene (26) being formed close to quantitatively. In contrast, photolysis of the 1,5-dimethylnaphthalene/tetranitromethane charge-transfer complex in 1,1,1,3,3,3-hexafluoropropan-2-ol gave sub stantial amounts of adduct (19), together with 1,5-dimethyl-4-nitronap hthalene (26) as the major product. Allylic rearrangements of xy-4-nit ro-1-trinitromethyl-1,4-dihydronaphthalene (34) and the epimeric l-1-n itro-4-trinitromethyl-1,4-dihydronaphthalenes (38) are seen as the mod e of formation of -1-nitro-t-2-trinitromethyl-1,2-dihydronaphthalene ( 33) and the epimeric 1,4,5,8-tetramethyl- 1-nitro-2-trinitromethyl-1,2 -dihydronaphthalenes (36), respectively. X-Ray crystal structure deter minations are reported for adducts (19), (20), (22), (24) and (28), th e last compound being formed only on chromatography of reaction mixtur es.