Synthesis of 2-nitrophenylhydrazine

Preparation of 2-nitrophenylhydrazine

Preparation of 2-nitrophenylhydrazine

Preparation of 2-nitrophenylhydrazine

o-Nitroaniline (34.5 grams, 0.25 mole) is diazotized according to the standard procedure. The obtained diazonium solution is cooled in an ice-salt bath, and sodium carbonate is added to it slowly, with continuous mechanical stirring, until the solution is only very slightly acid to Congo red (about 18-20 grams is required). Care should be exercised that the soda is immediately dispersed so that no portion of the solution becomes alkaline; the temperature should be kept as near to 0°C as possible, and in no case should it be allowed to rise above 5° C. The last traces of free acid are then neutralized with a small amount of sodium bicarbonate. The solution is filtered through a fluted filter to remove a few brown flocks, and the clear, light yellow filtrate is poured with continuous stirring into a solution, cooled to 10° C, made by mixing 155 grams (0.55 mole) of sodium bisulfite solution and 21 ml (0.25 mole) sodium hydroxide solution. A clear, intensely greenish yellow solution, neutral to Congo red, is formed. Potassium chloride (120 grams) is now added to precipitate the difficultly soluble potassium salt of nitrophenylhydrazinedisulfonic acid, and stirring is continued until all of the potassium chloride is dissolved. The solution is made strongly acid with hydrochloric acid and after standing overnight in a cold place to complete the precipitation, the thick yellow paste is filtered off with suction, pressed out, and washed with a cold 10% potassium chloride solution. The filter cake, which should not weigh more than 170 grams when properly pressed out, is transferred to a porcelain dish and treated with 140 ml concentrated hydrochloric acid, added gradually while stirring with a pestle. Stirring is continued until a completely homogeneous paste is formed, and the mixture is allowed to stand at room temperature for 4 hours. Then it is warmed on a water bath, again stirring thoroughly with a pestle, until the yellow, finely crystalline paste is converted to a coarsely crystalline, light red suspension of o-nitrophenylhydrazine hydrochloride. Heating on the water bath is continued for another 15 minutes, during which neither resinification nor the smell of nitrobenzene should be noticeable. The mixture is placed in the cold chest overnight, then filtered with suction and washed with a cold mixture of equal volumes concentrated hydrochloric acid and water. The filter cake is dissolved in 300 ml lukewarm water and filtered to remove a small residue of brown flocks; then most of the hydrochloric acid is neutralized with 25 ml 25% ammonia (the solution should still be acid to litmus; otherwise it is acidified with acetic acid). The precipitation is completed by adding a solution of 15 grams of crystalline sodium acetate in 40 ml water. The mixture is chilled thoroughly, and the orange-red crystals are filtered off with suction. The filtrate should be tested with more acetate to see that no more precipitation occurs. The precipitate is washed with cold water and dried at about 80°C. in a steam heated drying oven. The yield of product is about 30 grams, or 70-80% of the theoretical amount. This product is suitable for most purposes without further treatment. Recrystallization alcohol gives completely pure o-nitrophenylhydrazine in the form of slender brown plates with a bluish surface reflection, melting sharply at 91-93° C.

The fundamental processes of dye chemistry, by H. E. Fierz-David, 62-63, 1949





InChI Key


Canonical SMILES


MeSH Synonyms

2-nitrophenylhydrazine, 2-nitrophenylhydrazine hydrochloride, 2-nitrophenylhydrazine monohydrochloride, 2-NPH, o-nitrophenylhydrazine

Depositor-Supplied Synonyms

2-Nitrophenylhydrazine, (2-Nitrophenyl)hydrazine, 3034-19-3, HYDRAZINE, (o-NITROPHENYL)-, o-NITROPHENYLHYDRAZINE, FRBUNLLUASHNDJ-UHFFFAOYSA-N, EINECS 221-222-6, SBB055375, BRN 0512797, 2NitroPhenylHydrazine, o-nitrophenyl hydrazine, (2-nitrophenyl)diazane, PubChem12859, ACMC-1AGTI, (o-Nitrophenyl)hydrazine, Hydrazine, (nitrophenyl)-, N21588_ALDRICH, Hydrazine, (2-nitrophenyl)-, SCHEMBL297021, 1-(2-Nitrophenyl)hydrazine #, AC1MO527, CTK3C7152, MolPort-001-761-872, ZINC3860653, 6293-87-4 (mono-hydrochloride), ANW-26842, ZINC03860653, AKOS000200488, MCULE-7882000128, RTR-013046, TRA0050259, VZ25116, AJ-46037, AK-76919, CJ-10875, KB-25757, LS-76925, OR177071, ST2414206, TR-013046, 4CH-013744, FT-0613212, N0413, ST50949437, B-9157, AB00443778-03, 4-15-00-00304 (Beilstein Handbook Reference), A820331, I01-3590, T5501914, InChI=1/C6H7N3O2/c7-8-5-3-1-2-4-6(5)9(10)11/h1-4,8H,7H, 3034-93-3, 86490-48-4

Removed Synonyms

CID3314739, 6293-87-4

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