N,N-Dimethylaniline: Properties, Analysis and Application

N,N-Dimethylaniline is a tertiary amine used as an intermediate in the manufacture of vanillin, mirex, methyl violet and other dyes, and as a solvent, alkylating agent and stabiliser.

Properties of N,N-Dimethylaniline

• Apearences: Yellowish to brownish oily liquid
  

• Density: 0.956 g/ml at 20 °C

• Boiling-point: 192–194 °C
  

• Melting-point: 2–2.45 °C
  

• Solubility: Insoluble in water (2–14 g/1 at 25 °C). Since N,N-dimethylaniline is a basic compound, its solubility is dependent on the pH of the aqueous medium: its solubility in water at pH > 7 is lower than that in water of pH < 5. The data on aqueous solubility reported in the literature thus vary widely. Soluble in acetone, benzene, chloroform, diethyl ether and ethanol
  

• Volatility: Vapour pressure, 1 mm Hg [133 Pa] at 29.5 °C
  

• Stability: Slowly oxidizes and darkens in air; can react with nitrous acid to form ring-substituted nitroso compounds
  

• Octanol/water partition coefficient (P): 2.31
  

Analysis of N,N-Dimethylaniline

N,N-Dimethylaniline can be detected in air by adsorption on silica gel, desorption with ethanol and analysis by gas chromatography and flame ionization detection. The limit of detection is 10 µg/sample. Amines can be liberated during the manufacture of rubber, especially by vulcanization and by other thermal degradations. A method was described for the determination of free aromatic amines, including N,N-dimethylaniline, using high-temperature glass-capillary gas chromatography and nitrogen-selective detection (thermionic specific detector), with detection limits of 10–20 pg. A gas chromatographic procedure for the determination of residual N,N-dimethyl-aniline as a contaminant in commercial antibiotics has been described, which involves dissolution of the sample in aqueous alkali, extraction of N,N-dimethylaniline with cyclo-hexane and analysis by gas chromatrography-flame ionization detection.

Application of N,N-Dimethylaniline

N,N-Dimethylaniline is used as an intermediate in the manufacture of dyes, Michler's ketone and vanillin. It is also used as a specialty industrial solvent, a rubber vulcanizing agent, a stabilizer and an acid scavenger.