There are three isomers of toluidine, which are organic compounds discovered and named by James Sheridan Muspratt and August Wilhelm von Hofmann in 1845.
[1] These isomers are o-toluidine, m-toluidine, and p-toluidine, with the prefixed letter abbreviating, respectively, ortho; meta; and para.
All three are aryl amines whose chemical structures are similar to aniline except that a methyl group is substituted onto the benzene ring.
Due to the amino group bonded to the aromatic ring, the toluidines are weakly basic.
ortho- and meta-toluidines are viscous liquids, but para-toluidine is a flaky solid.