Patent ID: 8846975

Claim:
A process for preparing a dicarboxylic acid, the process comprising preparing the dicarboxylic acid having a structure of formula (I), in which n represents an integer from 1 to 9, in a single step, by action of nitric acid, in the presence of one or more oxides of nitrogen selected from NO,NO 2 , N 2 O 3 , N 2 O 4 , N 2 O 5 , NO 3 , N 2 O 6 , N 4 O and mixtures thereof, at a molar concentration in the reaction mixture of greater than 2.5 mmol of oxides per kg of reaction mixture, from a compound of formula (II) or (III) in which n represents the same integral number as in the formula (I) wherein the nitric acid in aqueous solution is added in the reaction mixture and wherein said process uses a molar ratio R, corresponding to the number of moles of oxides of nitrogen added to the reaction mixture relative to the number of moles of substrate compounds (II) or (III) to be oxidized, and said radar ratio is gareater than or equal to 1.5.