(127a) Nitration of Aromatic Compounds without Using Sulphuric Acid

Abstract: Green Chemistry is becoming the worldwide term used to describe clean, environmentally friendly, sustainable chemical technology; the core principle being to eliminate the generation of hazardous substances during chemical manufacture and use. It has been tried to apply the same approach here for the nitration process. Nitration is one of the most important reactions in synthesis of organic compounds because of their wide range of applications like solvents, dyes, pharmaceuticals & explosives. Nitration development is a complex, lengthy and expensive process. The majority of organic nitration requires the use of sulfuric acid or oleum in the nitric acid because sulfuric acid is present as catalyst, solvent and dehydrating agent. Also, in about 94% sulfuric acid, the nitric acid practically completely ionized to nitryl ion. Utilization of sulfuric acid produce contaminated and diluted spent acid stream. As environmental legislation become more stringent, this spent acid must be treated and recovered. 1. Discharge without treatment of spent acid is not an acceptable solution. 2. Neutralization of spent acid stream with lime is still practiced, particularly in cases in which the quantity of acid is relatively small. However in many cases the gypsum is not of saleable quality and must be stockpiled leading to concerns that contaminants in the gypsum may be leached into the ground water. 3. Direct use of nitration spent acids in other industries is rarely possible due to the presence of residual nitric/nitrous species and organic contaminants. Considering above explained disadvantages associated with nitration in presence of sulfuric acid, the study has been performed with objective to find alternate routes to carry out nitration without the use of sulfuric acid. In this work, various experiments were carried out on p-toluidine (aromatic amine). p-Toluidine nitro product is used for dyeing cotton, viscose and the chromogenic agent for printing. p-Toluidine is aromatic amine and nitration of aromatic amine is to be done in three steps as: 1. Protection of amine group by acylation, 2. Nitration of amide and 3. Removal of acetyl group. After extensive literature search following nitrating agents have been selected: (I). HNO3 with AcOH, (II). HNO3 & NaNO2 with AcOH, (III). HNO3 with CH2Cl2, (IV). HNO3 & NaNO2 with CHCl3, (V). HNO3 & NaNO2 with CH2Cl2, (VI). NH2CONH2 HNO3 with Polyphosphoric Acid. Experiments have been carried out in chemistry laboratory and the general experimental procedure was followed during each stage of experimentation. Analysis of intermediate/final product is performed using Thin Layer Chromatography (TLC) and melting point verification after particular stage of experimentation. The desired nitro-product is achieved after successful nitration with (IV) and (V) and verification of final product has been confirmed with mass spectroscopy analysis. Conclusively, nitration of p-toluidine can be possible without using sulfuric acid.