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tropolystyrene. Typical Dumas nitrogen analyses were in the range 9.23-9.41%; theory 9.39%.In the preferred method a solution of polystyrene (0.8-1.0 M) in methylene chloride at 5 °C was treated with mixed acid (HNO3 36.0, H2SO4 52.5, H20 11.5 wt %) containing 2.0 mol of nitric acid over 10 min. The mixture was then brought to reflux (40 °C). The nitro polymer precipitated in about 5 min. The mixture was held at reflux for 2-4 h, and the methylene chloride was decanted from the polymer. The solvent can be reused directly. The polymer was washed three times with methylene chloride and three times with hot water prior to analysis, which showed 99.0% of mononitration.Nitric Acid Oxidations. The nitrated bibenzyl (or diphenylpropane) mixtures were oxidized by heating 0.1 mol of nitro compound, 0.5 mol of 70% nitric acid, and 160 mL of water in a titanium-lined shaker tube at 180 °C for 5-6 h. The crude product was collected on a filter, washed with water, then dissolved in dilute sodium bicarbonate or ammonia solution to permit separation of about 1 g of deep yellow neutral material, mp 130-190 °C, a mixture of starting material with dinitrobenzyl. The filtrate was acidified to yield p-nitrobenzoic acid. From pure 4,4,-dinitrobibenzyl, 27.0 g, 81% was obtained, mp 243.5-244.5 °C. Dinitrodiphenylpropane was oxidized similarly to 41% of p-nitrobenzoic acid.Nitropolystyrene was oxidized similarly, but it was then discovered that 10-20% of the p-nitrobenzoic acid was destroyed during the prolonged treatment. Presumably, the yields in the preceding paragraph could have been higher with shorter contact times. Optimum yields were obtained by accepting less than quantitative conversions. Nitropolystyrene was heated with 22.2% HNO3 (6.4 mol per ring) for 1 h at 180 °C. Product isolation as described above gave 20-30% of neutral material (which can be recycled) and 87-89% of pnitrobenzoic acid (corrected for unoxidized starting nitropolystyrene). Oxidation at 150 °C, 6 h or 210 °C, 1 h, was much less satisfactory. With 11% nitric acid, the oxidation was very sluggish.Literature Cited