Aminobenzene: A Versatile Building Block for Organic Synthesis
Aminobenzene, also known as aniline or phenylamine, is an organic compound with the formula C6H5NH2. It consists of a benzene ring with an amino group attached to it. Aminobenzene is a colorless liquid with a characteristic odor and a boiling point of 184 Â°C. It is slightly soluble in water and readily soluble in organic solvents such as ethanol, ether and chloroform.
Aminobenzene is one of the most important aromatic amines in organic chemistry. It is a precursor to many industrial chemicals, such as dyes, drugs, pesticides, plastics and rubber. Aminobenzene can undergo various reactions, such as electrophilic aromatic substitution, nucleophilic aromatic substitution, oxidation, reduction and condensation, to form a wide range of derivatives with different functional groups and properties.
In this article, we will review some of the most common and useful reactions of aminobenzene and its derivatives, and show how they can be applied to synthesize various organic compounds.
Electrophilic Aromatic Substitution
Electrophilic aromatic substitution (EAS) is a reaction in which an electrophile (E) replaces a hydrogen atom on an aromatic ring. Aminobenzene is highly reactive towards EAS because the amino group is an activating and ortho/para-directing group. This means that the amino group increases the electron density on the ring and makes it more attractive to electrophiles, and that the electrophiles preferentially attack the positions ortho or para to the amino group.
Some examples of EAS reactions of aminobenzene are:
Nitration: Treatment of aminobenzene with nitric acid and sulfuric acid produces nitrobenzene (C6H5NO2) and 4-nitroaniline (C6H4NH2NO2). Nitrobenzene is an important intermediate for the synthesis of aniline and other aromatic amines. 4-Nitroaniline is used as a dye intermediate and an antiseptic agent.
Sulfonation: Treatment of aminobenzene with fuming sulfuric acid produces benzenesulfonic acid (C6H5SO3H) and 4-aminobenzenesulfonic acid (C6H4NH2SO3H). Benzenesulfonic acid is used as a catalyst and a detergent. 4-Aminobenzenesulfonic acid is used as a dye intermediate and a precursor to sulfanilamide, a sulfa drug.
Halogentation: Treatment of aminobenzene with chlorine or bromine in the presence of an iron catalyst produces chlorobenzene (C6H5Cl) or bromobenzene (C6H5Br) and 4-chloroaniline (C6H4NH2Cl) or 4-bromoaniline (C6H4NH2Br). Chlorobenzene and bromobenzene are used as solvents and starting materials for other organic compounds. 4-Chloroaniline and 4-bromoaniline are used as dye intermediates and pharmaceuticals.
Friedel-Crafts alkylation: Treatment of aminobenzene with an alkyl halide (R-X) in the presence of an aluminum chloride catalyst produces alkylbenzene (C6H5R) and 4-alkylaniline