1. Chemical Structure and Properties

• Molecular Formula: C₆H₇N

• Structural Formula: C₆H₅–NH₂ (A benzene ring directly attached to an amino group).

• Appearance: Colorless to slightly yellow oily liquid, darkens on exposure to air and light.

• Boiling Point: 184 °C

• Density: 1.02 g/cm³ at 20 °C

• Solubility: Moderately soluble in water (3.6 g/100 mL at 20 °C); soluble in ethanol, ether, and most organic solvents.

• Odor: Characteristic aromatic, amine-like smell.

• Chemical Behavior:

• Weak base compared to aliphatic amines due to electron-withdrawing benzene ring.

• Undergoes electrophilic substitution (nitration, sulfonation, halogenation).

• Easily oxidized in air, leading to dark-colored products.

  
  

2. Industrial Applications

• Dye Industry: Primary raw material for azo dyes, indigo dyes, and aniline black.

• Polyurethane Production: Intermediate for methylene diphenyl diisocyanate (MDI), essential in polyurethane foams.

• Pharmaceuticals: Precursor for paracetamol (acetaminophen), sulfa drugs, and local anesthetics.

• Rubber Industry: Used to manufacture antioxidants and vulcanization accelerators.

• Agriculture: Intermediate in herbicides and pesticides (e.g., 2,4-D).

  
  

3. Safety and Toxicology

• Health Hazards:

• Toxic by inhalation, ingestion, or skin absorption.

• Can cause methemoglobinemia (reduces oxygen-carrying capacity of blood).

• Symptoms: cyanosis, headache, dizziness, respiratory distress.

• Exposure Limits:

• OSHA PEL: 5 ppm (skin)

• ACGIH TLV: 2 ppm (TWA)

• Flammability:

• Combustible liquid, flash point 70 °C.

• Emits toxic fumes of nitrogen oxides upon combustion.

• Protective Measures:

• Use of chemical-resistant gloves, goggles, respirators, and adequate ventilation.

• Emergency showers and eyewash stations recommended in workplace.

  
  

4. Environmental and Regulatory Considerations

• Ecotoxicology:

• Toxic to aquatic organisms (LC50 for fish: 100 mg/L).

• Risk of bioaccumulation in soil and water.

• Biodegradability: Moderate; may persist in the environment under anaerobic conditions.

• Regulatory Compliance:

• EU REACH: Classified as toxic (Carc. 2, Acute Tox. 3, Skin Sens. 1).

• US EPA: Hazardous substance under TSCA and TRI reporting list.

• China: Listed as a hazardous chemical under GB 13690-2009.

• Transport:

• UN Number: UN 1547

• Hazard Class: 6.1 (Toxic substances)

• Packing Group: II

  
  

5. Case Studies and Application Insights

• Polyurethane Industry: Over 70% of global aniline demand is for MDI production, crucial in insulation foams and coatings.

• Pharmaceuticals: Acetanilide and paracetamol synthesis highlight its importance in drug manufacturing.

• Dyes: Historically central to synthetic dye industry; today still important for specialty dyes and pigments.