o-Anisidine (2-anisidine) is an organic compound with the formula CH3OC6H4NH2. A colorless liquid, commercial samples can appear yellow owing to air oxidation. It is one of three isomers of the methoxy-containing aniline derivative.
It is prepared via methanolysis of 2-chloronitrobenzene:[1]
NaOCH3 + ClC6H4NO2 → CH3OC6H4NO2 + NaClThe resulting o-nitroanisole is reduced to o-anisidine.
o-Anisidine is used in the manufacture of dyes. It is nitrated to give 4-nitroanisidine. It is also a precursor to o-dianisidine.
One special use is as a heartwood indicator. An acid solution of o-anisidine is diazotized by adding a sodium nitrite solution. This mixture is applied to the wood and by reaction with polyphenols in the heartwood a reddish brown azo dye is formed.
o-Anisidine is a dangerous pollutant from the production of dyes. It is listed as RCRA hazardous waste, with the code K181.[2] The International Agency for Research on Cancer (IARC) has classified o-anisidine as a Group 2B, possible human carcinogen.[3]