A novel method for the nitration of deactivated aromatic compounds

Novel nitration systems comprising nitric acid, trifluoroacetic anhydride a nd zeolite H beta, with or without acetic anhydride, are described. The sys tem having no acetic anhydride is more active and readily nitrates deactiva ted substrates such as nitrobenzene, benzonitrile, benzoic acid or 4-nitrot oluene to give predominantly the product substituted meta to the deactivati ng group. The system incorporating acetic anhydride is more moderate in activity, and nitrates moderately deactivated systems such as halogenobenzenes quantitat ively within two hours at ice-salt bath temperature, and provides very high selectivity for the para-nitrated product. This system also nitrates 2-nit rotoluene to give high selectivity for 2,4-dinitrotoluene production. Furth ermore, the system can be used for direct double nitration of toluene and g ives a 92% yield of 2,4-dinitrotoluene with a 2,4-:2,6- dinitrotoluene rati o of 25:1. Even greater selectivity (96% yield and 70:1 selectivity) can be achieved in the latter reaction by conducting the reaction in one flask bu t in two stages, with trifluoroacetic anhydride added only in the second st age.