Preparation of 2, 4-Dinitrodiphenylamine
Claim: The evidence will show that the red solid collected after recrystallization from the nucleophilic aromatic substitution of 2, 4-dinitrobromobenzene and aniline has the characteristics of 2, 4-dinitrodiphenylamine. Evidence: The procedure was carried out as described by Ault1 and the lab manual2. 2,4-dinitrobromobenzene (0.92g, 3.75mmol, pale yellow solid) and aniline (0.7mL, 0.7g, 7.5 mmol) were boiled in ethanol (10mL) under reflux until all solid dissolved. After the mixture cooled to room temperature, short, red needles were collected by suction filtration. The product was then recrystallized in the presence of 95% ethanol producing long red needles. 0.536g, 2.07mmol, 158-160°C (160°C lit3), 54.6% recovery. Thin layer chromatography was performed in three different eluents, hexane, toluene, and acetone. The chromatography compared aniline, 2, 4-dinitrobromobenzene, and a sample from the mixture of the two reactants when the reaction first began to take place. Another thin layer chromatography used a product sample an hour after the reaction first began and the eluent that showed the best separation of molecules. Table of Rf Values
Table of Rf Values
| Aniline| Product| 2, 4-Dinitrobromobenzene|
Toluene| 0.083| 0.104| 0.333| 0.583| Did not show up on plate| Hexane| 0| 0.043| 0.065|
Acetone| 0.836| 0.872| 1|
Toluene (pdt.1hr later)| 0.200| 0.327| 0| 0.200| 0.600| 0.900| 0.900|
Discussion: 2, 4-Dinitrodiphenylamine was synthesized by a nucleophilic aromatic substitution of 2, 4-dinitrobromobenzene and aniline. This reaction is an addition-elimination reaction. The nitro groups stabilize the carbanion intermediate with resonance and inductive effect. Because there are nitro groups on the ring, the substitution will occur rapidly because the...