o-Anisidine (2-anisidine) is an organic compound with the formula CH<sub>3</sub>OC<sub>6</sub>H<sub>4</sub>NH<sub>2</sub>. 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 a building block for other more complex compounds.
It is prepared via methanolysis of 2-chloronitrobenzene:
The 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. The International Agency for Research on Cancer (IARC) has classified o-anisidine as a Group 2B, possible human carcinogen.