Photochemical nitration by tetranitromethane. XXXII adduct formation in the photochemical reaction of phenanthrene and tetranitromethane

Photolysis of the phenanthrene/tetranitromethane charge-transfer complex yields the triad of phenanthrene radical cation, nitrogen dioxide, and trinitromethanide ion. Recombination of this triad in dichloromethane at 20° gives 9-nitrophenanthrene (1), trans-10-trinitromethyl-9,10-dihydrophenanthren-9-yl nitrate (2a), trans-9-nitro-10-trinitromethyl-9,10-dihydrophenanthrene(2b), and trans-10-trinitromethyl-9,10-dihydrophenanthren-9-ol (2c). Adduct formation is partially suppressed when trifluoroacetic acid (0.7 M) is added to the dichloromethane solvent at 20°, the major product identified being 9-nitrophenanthrene (1). At -20° in dichloromethane, or in acetonitrile at 20°, 10′-nitro-9,9′,10,10′-tetrahydro-9,9′biphenanthren-10-yl nitrate (3) is formed, apparently by reaction of nitrogen dioxide with phenanthrene. X-Ray crystal structure determinations are reported for adducts (2a,b).