2,4-Dinitroaniline [97-02-9-A] C6H5N3O4
In a 1000 ml round-bottom flask, place 160 ml of ethanol and 14.7 g of 2,4-dinitrobromobenzene. By gentle heating in a water bath, all the 2,4-dinitrobromobenzene is dissolved. Subsequently, the clear yellow solution is mixed with 120 ml of concentrated ammonia solution, causing the color to change to orange and the solution to become cloudy. Another 120 ml of ethanol is added to the solution and it is gently heated again until the solution becomes clear. Once this is done, the round-bottom flask is tightly sealed with a stopper and left at room temperature for at least 4 days. During this time, intensely yellow crystals precipitate from the solution. These are filtered after 4 days and recrystallized from a mixture of approximately 120 ml of ethanol and 48 ml of water. Beautiful yellow crystals with a melting point of 180 °C are obtained. The yield is about 60% of the theoretical yield.
 |
 |
 |
Notes: (1) In the classic synthesis of 2,4-dinitroaniline, gaseous ammonia is introduced into a melt of 2,4-dinitrochlorobenzene and ammonium acetate over 6 hours. A very wide introduction tube must be used, and the effort is quite significant (see: Organic Syntheses, Coll. Vol. 2, p.221 (1943); Vol. 15, p.22 (1935)). Other methods use aqueous ammonia, but under pressure, requiring an autoclave. The advantage of the following synthesis is that it is performed at low temperatures and without pressure. However, the method is only suitable for small quantities.
(2) The synthesis was carried out with the quantities given above. The reaction mixture was left to stand for about a week. The flask was cooled in an ice bath before filtering the crystals, which noticeably increased the amount of product precipitated. The recrystallized 2,4-dinitroaniline was dried in a desiccator over silica gel. 8.9 g of pure product was obtained (81% of the theoretical yield). The product was TLC-homogeneous (solvent: chloroform/acetone; substance applied as a solution in ethanol).
(3) 2,4-Dinitroaniline is used in the production of dyes and pigments (Permanent Red 2G) and in the synthesis of herbicides.
(4) The 2,4-dinitrobromobenzene was prepared analogously to 1-chloro-2,4-dinitrobenzene (see step 1 of the synthesis of 2,4-dinitrophenylhydrazine: 2,4-Dinitrophenylhydrazine) by nitrating 18.6 ml of bromobenzene with a nitrating acid consisting of 40.0 ml of fuming nitric acid and 80.0 ml of concentrated sulfuric acid. The extraction was performed with toluene more frequently than in the original protocol, and the toluene was not dried with calcium chloride before removal. Recrystallization from methanol yielded 35.5 g of pale yellow crystals (81% of the theoretical yield).
 |
 |
 |
 |
 |
Source: A. Ault, Techniques and Experiments for Organic Chemistry, 6th Edition, 1998, University Science Books
Delivered by: Heuteufel
Last updated: 19/10/2012
Other names: 2,4-Dinitro-1-aminobenzene; 2,4-Dinitrophenylamine; 2,4-Dinitraniline