Studies in aromatic nitration (nitration and acetoxylation with nitric acid-acetic anhydride).

1,4-Acetoxy-nitro adducts have been isolated from the reactions of a-xylene, £-xylene, hemimellitene and 3-bromoxylene with nitric acid-acetic anhydride mixtures. These have been shown to decompose into acetoxy-substituted aromatics. A cyclohexa-2,5-dienone has been isolated from the reactions of 4-bromo- and 4-acetoxy-oxylene with nitric acid-acetic anhydride, and this has been shown to decompose into two isomeric nitro-3,4-xylenols. The product distributions from the reactions of mesitylene, pseudocumene,ndurene, isodurene, prebnitene, pentamethylbenzene, hexamethylbenzene and 3- and 4-deutero-o-xylenes with nitric acid-acetic anhydride have also been determined. These data, and data from earlier work, are discussed in terms of a mechanism involving nitration at a methylated position, to form a carbonium ion which either adds acetate or loses a proton to give a transient methylenecyclohexadiene species. The kinetics of nitration of mesitylene, m-xylene, a-xylene, toluene and benzene in nitric acid-acetic anhydrideacetic acid have been investigated, either individually or by competition methods. The results are discussed in terms of the possible nitrating species in the system