Nitration of 1,3,5-trichloro-2,4-dinitrobenzene: nitro-denitration

Abstract

The title reaction effected in oleum at 150 °C gives a quantitative yield based on chlorine of a mixture of 1,3,5-trichloro-2,4,6-trinitrobenzene and 1,2,3,5-tetrachloro-4,6-dinitrobenzene; the dependence of product ratios on acidity, effects of additives, and results of isotopic-labelling studies indicates that the latter product is formed via reversible ipso-attack of nitronium ion at a nitro-substitute position followed by nucleophilic capture to give a diene which gives, possibly after oxidation, chlorine in an electrophilic form for reaction with starting material.