A Study On Oxidation Of Aromatic Side Chain With Nitric Acid

Alkylarenes oxidation reactions are of major importance in organic oxidation. The oxidation products and derivatives constitute a particular class in fine chemical intermediates, which have found a large number of uses from medicine, pesticide, dye, polymer materials and so on. It is valuable in the economic and social development.An efficient and practical method for the selective oxidation of polyalkybenzenes to the corresponding benzoic acid compounds with diluted nitric acid in autoclave has been reported in this thesis.In order to optimize the synthesizing process, the influences of nitric acid concentration, temperature and time on the selectivity and yield have been studied. It was found that the order of oxidation is Br>Cl>F>NO2, when the methyl group is para orientation. The position of the CH3 relative to the electron-withdrawing group also infected the oxidation (para>meta>ortho). Compare to the methods that described in the literatures, this synthetic method is better at simple work-up,without expensive catalyst, simple disposal, short reaction time, high conversion, high selectivity and good yield.A series of compounds, such as 4-nitro-3-methylbenzoic acid,4-fluoro-3-methyl benzoic acid,4-bromo-3-methyl benzoic acid,4-chloro-3-methylbenzoic acid,3-nitro-4-methylbenzoic acid,3-nitro-2-methylbenzoic acid,4-nitro-3,5-dimethylbenzoic acid and 4-fluoro-3,5-dimethyl benzoic acid have been synthesized with this new method. These compounds were characterized by 1H NMR or/and 13C NMR, respectively.Unfortunately, the results aren't satisfactory, owing to oxidation reactions of 2-fluoro-p-xylene and 2-bromo-p-xylene give poor selectivity.In addition, a low-costing method for synthesizing substitute aromatic dicar-boxylic acid has been studied in this paper. This synthetic strategy is superior to that described in the literatures in good yields, simple work-up,easily obtained materials and simple disposal.In that case, this route is easy to commercialize. We have synthesized 4-nitroisophthalic acid,4-fluoroisophthalic acid,4-bromoisophthalic acid, 4-chloroisophthalic acid, Nitroterephthalic acid,2-fluoroterephthalic acid,2-brom-oterephthalic acid,3-Nitrophthalic acid and biphenyl-4,4'-dicarboxylic acid by this novel method.