Nitric Acid → 2-Methyl-5-nitroimidazole

Participants

Reaction Steps

In a nitrator made of acid-resistant stainless steel of 75 liters capacity, provided with a reflux condenser, a mixer and a thermometer as well as a cooling mantle, there were dissolved 8 kg of 2-methylimidazole into a solution already nitrated as in example IV, and then 24 liters of nitric acid of 1.40 density were added in such a manner, that the temperature was maintained at 70°. Thereafter sulphuric acid of 1.84 density was added such that, by simultaneous stirring and cooling, a constant temperature was maintained. After addition of 10 liters of sulphuric acid, the introduction was interrupted and after 10 minutes the sulphuric acid was gradually introduced until a total quantity of 24 liters was used. The reaction proceeded progressively more intensively and the flow of cooling water was correspondingly increased. A supplementary reservoir in the form of a tank with a conduit enabled the introduction of 10 liters of already reacted nitrated solution to the nitrator--a similar device was used in all reactions which have begun at a low temperature. During and after addition of the entire quantity of sulphuric acid, the solution was continually stirred and cooled for 15 minutes, and then, after a clear diminution of the reaction and diminishing of the exothermic effect, a slow increase of temperature, degree by degree in one minute, was allowed until a temperature of 110° has been reached. The mixture was maintained at this temperature for 15 minutes more. Then the reflux condenser was disengaged, while simultaneously leading the liberated vapors and gases directly to the absorption device, and the flow of the cooling water was terminated. The temperature of the reacting mixture raised by itself, reaching at the end a temperature of 138°. At this temperature the reaction was completed in 20 minutes, whereby the solution was condensed by distilling off about 3 liters, mainly water and nitric acid (i.e. diluted nitric acid), whereby after this treatment the cooling of the mixture was reinstituted. In the nitrator, 20% of the volume of the solution was retained for the treatment of the following charge, and from the remaining quantity there was obtained in known manner 8.700 kg of 2-methyl-5-nitroimidazole corresponding to 70% of theoretical.

Provenance & Evidence