Toluidine is a colorless aromatic amine with the chemical formula C7H9N. It refers to a group of three isomers that differ in the position of a methyl group (CH₃) bonded to a benzene ring relative to an amino group (NH₂) attached to the same ring. These isomers are o-toluidine, m-toluidine, and p-toluidine.
Toluidines are weakly basic and poorly soluble in pure water. However, they dissolve well in acidic water due to the formation of ammonium salts. They are colorless liquids or solids depending on the isomer. p-Toluidine is a solid at room temperature, while o-toluidine and m-toluidine are liquids.
Toluidines are mainly used as precursors in the production of dyes and pigments. They are also used in the manufacturing of some herbicides and rubber accelerators. Toluidine is a component of Toluene Blue, a stain used in medicine to identify dead tissue.
Toluidines can be harmful if inhaled, ingested, or absorbed through the skin. Exposure to toluidines can cause irritation of the eyes, skin, and respiratory system. Long-term exposure to toluidines has been known to cause methemoglobinemia, a condition in which the blood is unable to carry enough oxygen.