Nitration of chlorobenzene to chlorodinitrobenzene Griesheim method

The nitration of chlorobenzene to chlorodinitrobenzene without separating the isomers of chloronitrobenzene is accomplished in two successive stages in the same nitrator. 

Mononitration. 3000 kg of chlorobenzene, boiling within a range of 0.8°C, is mixed with the spent acid from dinitration, containing 78% of H2S04. Then 1850 kg of a nitrating mixture of the compositions  

The whole is heated to 70°C and stirred for 2 hr at 70-80°C. Nitration is complete if a sample of the product has a melting point of 47.6°C, and, when steam distilled after being brought to alkalinity, the distillate does not smell of o- nitro-phenol. After nitration has been completed, the whole is cooled to 50°C diluted at this temperature with 390 kg of water and allowed to remain at rest for separation. The lower spent acid layer, containing 78% of H2S04 is used for mononitration. 

Chlorodinitrobenzene forming the upper layer is washed with warm water, then with a warm dilute solution of sodium carbonate and again with warm water, until entirely free from acid. Then it is dried by heating under reduced pressure in a 20 m3 tank. 

From 100 parts of chlorobenzene 175 parts of chlorodinitrobenzene with a melting point of 47.6°C is obtained, which corresponds to 97.5% of the theoretical yield. 

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Nitration ofp chIoronitrobenzene to l-chloro-2,4>dinitrobenzene Nitration of chlorobenzene to chlorodinitrobenzene (Griesheim method) Mononitration Dinitration... 

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