Aniline

Aniline is the aromatic amine C₆H₅NH₂, consisting of an amino group attached to a benzene ring. It is a key feedstock for dyes, pharmaceuticals, and other chemicals.

Resonance: The delocalization of electrons across multiple atomic arrangements in a molecule or ion. The nitrogen lone pair is partly delocalized into aniline’s benzene ring.
Aniline dyes: Synthetic dyes derived from aniline or related aromatic amines. Aniline became the starting material for a major family of synthetic colorants.
Coal tar: A complex liquid mixture produced when coal is heated in the absence of air. Early aniline production relied on aromatic compounds isolated from coal tar.
Methemoglobinemia: A disorder in which oxidized hemoglobin cannot carry oxygen effectively through the blood. Aniline exposure can oxidize hemoglobin and cause this potentially severe condition.
Basicity: The tendency of a chemical species to accept a proton or donate an electron pair. Aniline is less basic than aliphatic amines because its nitrogen lone pair is delocalized.
Mauveine: A purple synthetic dye discovered by William Henry Perkin in 1856 while oxidizing aniline-related materials. Its accidental discovery launched commercial aniline-dye manufacture.
Friedlieb Ferdinand Runge: A German chemist who isolated aniline from coal tar in the 1830s. His early isolation helped establish aniline as a distinct substance.
Occupational exposure: Contact with hazardous substances that occurs during work or job-related activities. Workers handling aniline may absorb it through the skin or inhale its vapors.
Electrophilic aromatic substitution: A reaction in which an electrophile replaces a hydrogen atom on an aromatic ring. The amino group activates aniline’s ring and directs many substitutions to ortho and para positions.
Methylene diphenyl diisocyanate: An aromatic diisocyanate used chiefly to make polyurethane foams, elastomers, and coatings. Aniline is converted through formaldehyde-derived intermediates into this major industrial chemical.

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