Hydroxamic acids analytical reagents

V. A VERY BRIEF REVIEW OF OXIMES, HYDROXAMIC ACIDS AND RELATED SPECIES AS ANALYTICAL REAGENTS FOR THE STUDY OF ORGANIC... 

Oximes, hydroxamic acids and related species are often used as reagents in inorganic analytical chemistry for precipitation, gravimetric and volumetric determinations as well as for preconcentration, extraction, derivatizations and subsequent determination of analyte using instrumental techniques. A brief review of analytical chemistry in general and of these species in particular follows. 

Our review on the use of oximes and hydroxamic acids in inorganic analytical chemistry showed that these reagents are/were most frequently used for gravimetric determinations, determinations based on complexation, spectrophotometric determinations and separations, while their use for column separations, as electrode sensors, as supporting electrolytes or compounds that enhance sensitivity of determination is less common. Additionally, it was noticed that the analytical chemistry of anions is less advanced than that of cations and for this reason this chapter was limited to analytical chemistry of metallic cations. 

Hydroxamic acids are biocides and lipogenase inhibitors. They are also of interest as reagents in analytical chemistry. Of first importance is the dependence of their acidity on structure. 

Formation constants of 3d metal ions with A-m-tolyl-p-substituted benzohydroxamic acids and of rare earths with thenoylhydroxamic acid have been determined. Formation constants of proton and metal complexes of iV-phenyl-2-thenoyl- and A-p-tolyl-2-thenoyl-hydroxamic acids have also been determined. In addition, study has been made of the mixed ligand complexes involving nicotine- and isonicotino-hydroxamic acids. A method of extraction and spectrophotometric determination of vanadium with chlorophenylmethylbenzohydroxamic acid has also been published. It may be mentioned that hydroxamic acids (in particular, the A-phenylbenzohydroxamic acid) have been widely used as analytical reagents for metal ions. Solvent extraction of titanium by benzo- or salicyl-hydroxamic acid in the presence of trioctylamine in the form of coloured complexes has been reported. A-w-Tolyl-p-methoxybenzohydroxamic acid has been used for extraction and spectrophotometric determination of Mo and W from hydrochloric acid media containing thiocyanate. 

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