Patent GB-592219-A (GB)
Title: Improvements relating to the nitration of organic compounds
IPC: C07C203/04
Filed: 1944-01-15
Abstract: Nitric acid is formed during the nitration of organic materials by means of nitrogen pentoxide in an inert non-aqueous diluent (see Group IV) and is eliminated by means of a reagent which is inert towards nitrogen pentoxide but which will react with the nitric acid, the inert diluent being one which dissolves nitrogen pentoxide but not the reagent which reacts with nitric acid and any product (other than nitrogen pentoxide) of that reaction. Phosphorus pentoxide is a suitable reagent, yielding with nitric acid nitrogen pentoxide and metaphosphoric acid.  Specified solvents are chloroform, carbon tetrachloride, propylene dichloride and those of coal tar or petroleum origin.ALSO:A nitration process for organic materials comprises bringing an inert non-aqueous diluent in which nitrogen pentoxide is dissolved into contact with the material to be nitrated, whereupon nitric acid is liberated in the liquid during the nitrating process and simultaneously or subsequently bringing the liquid into contact with a reagent which is inert towards nitrogen pentoxide, but which will react with the liberated nitric acid to eliminate it from its reaction zone substantially as it is formed, the diluent being one which dissolves nitrogen pentoxide, but not the reagent which reacts with nitric acid and any product (other than nitrogen pentoxide) of that reaction.  Phosphorus pentoxide is specified as such a reagent, yielding with nitric acid nitrogen pentoxide and metaphosphoric acid.  The process may be carried out batchwise by treating the organic material with the nitrogen pentoxide solution following which or simultaneously, the solution is treated with phosphorus pentoxide.  Alternatively, the nitrogen pentoxide solution may be circulated continuously first in contact with the organic material and then in contact with the phosphorus pentoxide, whereby the nitric acid formed is eliminated before the liquid is again brought into contact with the organic material, the diluent being one in which the organic material is insoluble. A series of nitrating and regenerating chambers may be so used. In such a continuous process, the organic material may be continuously moved, for example, in counter-current to the nitrating solution.  When the organic material is soluble in the diluent, nitration is preferably effected in the presence of the phosphorus pentoxide.  Organic materials which may be nitrated by the process are hydrocarbons, carbohydrates and polysaccharides, i.e. starches, celluloses and sugars such as lactose and sucrose, alcohols such as pentaerythritol, mannitol and glycerol and amines.  The nitrating solutions preferably contain 5 to 50 grams N2O5 per 1000 c.cs. of solution and may be used in excess.  Nitration is normally carried out at below 30 DEG  C. Sufficient phosphorus pentoxide is used to ensure absorption of the nitric acid and regeneration of nitric acid.  The diluents are preferably those in which the nitrated organic material is insuluble; chloroform, carbon tetrachloride and propylene dichloride are specified.  Examples describe the nitration of corn-starch, cellulose, penta-erithrytol, toluene and dimethyloxamide (yielding the dinitro derivative).