4-Aminopheno is also known as hydroxyaniline and amino-hydroxybenzene. 

There are three isomers, namely o-aminophenol, m-aminophenol, p-aminophenol (4-aminophenol). Para-aminophenol was first prepared by Baeyer et al. in 1874. Because of the different relative positions of hydroxyl group and amino group, the three are also different in terms of physical and chemical properties. This product shows weak alkalinity, weak acidity and strong reducibility. Because it has two groups of amino and phenol at the same time, it has the commonality of both. It is very unstable in the air and sunlight, especially in the wet air is sensitive to oxygen, especially the ortho-position and para-position are more likely to be oxidized and the color is deepened, mainly to form amino phenoxazine derivatives after oxidation. The main uses of aminophenol are as dye intermediates and photographic developers. It can manufacture acid dyes, direct dyes, sulfide dyes, azo dyes, mordant dyes and fur dyes. M-aminophenol and p-aminophenol are raw materials for medicine, herbicides, fungicides, insecticides and thermistors. O-aminophenol is also used as an inhibitor of metal alkaline corrosion, hair dye, rubber anti-aging agent, antioxidant, stabilizer, petroleum additive, catalyst of organic reaction, chemical reagent (m-aminophenol is a gold and silver verification reagent), intermediate of organic synthesis, etc.