OXIDATION OF 1,1-DIARYLALKANES

A process for the preparation of a diarylketone from the corresponding 1,1-diarylalkane is characterized by oxidizing said 1,1-diarylalkane with an aqueous solution containing nitric acid to obtain a reaction mixture containing an organic and an aqueous phase, separating said organic from said aqueous phase, further subjecting said organic phase to oxidation with nitric acid, to obtain a reaction mixture containing the desired diarylketone and an aqueous phase and thereafter separating the diarylketone from this aqueous phase. By "nitric acid" is meant any of the oxides NO, NO2, N2O4, N2O5 or N2O3 when made into aqueous solutions. The 1,1-diarylalkane may be represented by the general formula wherein R and R1 are aryl radicals containing one or more rings, e.g. phenyl, biphenyl, naphthyl, phenanthryl, anthryl, indyl, dihydronaphthyl or cyclohexylnaphthyl. These radicals may carry up to five nuclear substituents as defined by R2, where R2 is primary, secondary or tertiary alkyl or is F, Cl, Br, I, NO2, SO3H, COOH, COOR (where R is alkyl), NH2 or OH. Many specific examples of such alkanes are given and include 1-(2-methyl, 4-chlorophenyl),1 - (2 - ethylphenyl)octane, 1 - (4-methyl - 2 - nitrophenyl),1 - (2 - methyl, 4 - isopropylphenyl)ethane, 1 - (2 - propyl, 3 - carboxynaphthyl),1 - (4 - butylphenyl)hexane, 1-(2 - propyl, 3 - aminophenyl),1 - (4 - methyl - 2-sulphophenyl)ethane, 1,1 - bis - (4 - methylphenyl)ethane and 1,1-bis-(3,4-dimethylphenyl)ethane. In the case of compounds containing nuclear-substituted alkyl groups on the aryl radicals the product will be a ketone carboxylic acid. The first oxidation is suitably conducted with 1-70% (by weight), aqueous HNO3 at a temperature between 80-300 DEG C., and a pressure between 0-70 kg./cm.2 gauge for 1 minute to 48 hours. The reacting-weight ratio of alkane to acid can vary between 100 : 1 to 1 : 100. The second oxidation is suitably conducted with 5-100% aqueous HNO3, at a temperature between 110-350 DEG C., and a pressure of 7-70 kg./cm.2 gauge, for a time in excess of ten minutes. The weight ratio of the reactants can be from 3 : 1 to 100 : 1 of HNO3 to organic phase. In a preferred embodiment, the aqueous acid remaining from the second oxidation is cycled back to the first oxidation step for further reaction. The desired diarylketone product is separated by conventional means and may be washed with a solvent to remove impurities. Trimellitic acid is stated to be among by-products of