A hydroxamic acid is a class of chemical compound

Chemical compound

A chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...

s sharing the same functional group

Functional group

In organic chemistry, functional groups are specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules. The same functional group will undergo the same or similar chemical reaction regardless of the size of the molecule it is a part of...

 in which an hydroxylamine

Hydroxylamine

Hydroxylamine is an inorganic compound with the formula NH2OH. The pure material is a white, unstable crystalline, hygroscopic compound. However, hydroxylamine is almost always provided and used as an aqueous solution. It is used to prepare oximes, an important functional group. It is also an...

 is inserted into a carboxylic acid

Carboxylic acid

Carboxylic acids are organic acids characterized by the presence of at least one carboxyl group. The general formula of a carboxylic acid is R-COOH, where R is some monovalent functional group...

. Its general structure is R-CO-NH-OH, with an R as an organic residue, a CO as a carbonyl

Carbonyl

In organic chemistry, a carbonyl group is a functional group composed of a carbon atom double-bonded to an oxygen atom: C=O. It is common to several classes of organic compounds, as part of many larger functional groups....

 group, and a hydroxylamine

Hydroxylamine

Hydroxylamine is an inorganic compound with the formula NH2OH. The pure material is a white, unstable crystalline, hygroscopic compound. However, hydroxylamine is almost always provided and used as an aqueous solution. It is used to prepare oximes, an important functional group. It is also an...

 as NH₂-OH. They are used as metal chelator

Chelation

Chelation is the formation or presence of two or more separate coordinate bonds between apolydentate ligand and a single central atom....

s
in industry, e.g. benzohydroxamic acid and others in the reprocessing of irradiated fuel.
Hydroxamic acids can be synthesized from aldehyde

Aldehyde

An aldehyde is an organic compound containing a formyl group. This functional group, with the structure R-CHO, consists of a carbonyl center bonded to hydrogen and an R group....

s via the Angeli-Rimini reaction

Angeli-Rimini reaction

The Angeli-Rimini reaction is an organic reaction between an aldehyde and the sulfonamide N-hydroxybenzenesulfonamide in presence of base forming an hydroxamic acid....

.