A DISTILLATION METHOD OF AROMATIC NITRATION USING AZEOTROPIC NITRIC-ACID

The possibility of using a nitric acid-water azeotrope for the nitration of chlorobenzene has been investigated.When the reaction is carried out under continuous distillation to remove the water produced as it is formed, yields of nitrochlorobenzene in excess of 80% theoretical are obtained. The isomer proportions in the nitro productare 39% 2-nitro-, 1% 3-nitro-, and 60% 4-nitro-chlorobenzene. However, at room temperature, part of the nitro product is liquid. The phase diagram for mixtures of the 2- and 4-nitroisomers shows a eutectic mixture containing 67% 2-nitro- and 33% 4-nitrochlorobenzene, having a freezing point of ca. 16 °C. The fraction of the nitro products that is liquid at room temperature has a composition close to this. Methods of obtaining pure 4-nitro chlorobenzene from the products have been demonstrated. © 1990, American Chemical Society. All rights reserved.