A hydroxamic acid is a class of chemical compounds sharing the same functional group in which an hydroxylamine is inserted into a carboxylic acid. Its general structure is R-CO-NH-OH, with an R as an organic residue, a CO as a carbonyl group, and a hydroxylamine as NH2-OH. They are used as metal chelators in industry, e.g. benzohydroxamic acid and others in the reprocessing of irradiated fuel. 
Iron is a key component of cytochromes and iron-sulphur proteins (involved in electron transport) and is thus important in cellular respiration. In an environment, absent from oxygen (anoxic); iron will be present in the ferrous +2 oxidation state (Fe2+), which is water-soluble. Under oxic conditions; iron will be in the ferric +3 oxidation state (Fe3+), in insoluble mineral form. The powerful chelating properties of hydroxamic acid and its derivatives is exploited by bacteria to obtain ferric iron. Once the iron-hydroxamate complex has entered the cell, the iron is liberated and the hydroxamic acid can be excreted and reused for iron transport.
Hydroxamic acid is used extensively in floatation of rare earth minerals during the concentration and extraction of ores to be subjected to further processing.
Possible use against cancers
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