[12232-99-4] · BiNaO3 · Sodium Bismuthate · (MW 279.97)
(selective oxidant for cleavage of 1,2-diols1)
Physical Data: somewhat uncertain composition corresponding to around 85% NaBiO3.
Solubility: insoluble in common solvents.
Form Supplied in: amorphous powder.
Sodium bismuthate is a selective reagent for the oxidative cleavage of 1,2-diols, somewhat similar in scope to periodate or Lead(IV) Acetate.1 The reagent, an insoluble powder, is used as a suspension in aqueous or organic solvents, normally acidified with Acetic Acid or Phosphoric Acid. The color and reactivity of commercial samples is somewhat variable. 1,2-Diols are rapidly cleaved to the corresponding carbonyl compounds by sodium bismuthate at moderate temperatures. Like lead tetraacetate but unlike periodate, sodium bismuthate also cleaves a-hydroxy carboxylic acids and some a-hydroxy ketones.2,3 The general cleavage reactions of sodium bismuthate include the transformations of eqs 1-3 (R = H or alkyl).
Sodium bismuthate is sometimes preferred to lead tetraacetate because anhydrous conditions are not required for its use. The diol fission reactions of sodium bismuthate are carried out in an excess of acetic or phosphoric acid. When acetic acid is used, a reddish brown suspension, assumed to be bismuth(V) oxide, is formed initially and gradually disappears as the reaction proceeds, leaving a solution of bismuth triacetate. When the reagent is used in combination with phosphoric acid, an orange yellow suspension of unknown composition forms initially. As the oxidation takes place, this gives way to a white precipitate of bismuth triphosphate.
Even analytical-grade samples of sodium bismuthate display an oxidizing capacity which corresponds to about 85% NaBiO3. Reactions may be carried out in 100% or aqueous acetic acid at, or slightly above, room temperature. A clear colorless solution remains when reaction is complete. Bismuth may be conveniently removed from the reaction by precipitation as the phosphate. Complete reaction may take from a few minutes to several hours.
One application of sodium bismuthate which has received considerable attention is the analytical determination of urinary corticosteroids.4 This technique relies on the selective cleavage of the corticosteroid side chain. Analysis of the reaction products for 17-keto steroids and formaldehyde is then used to identify the corticosteroids originally present.
Various other oxidation reactions of sodium bismuthate have been studied in addition to 1,2-diol and related cleavage processes. The reagent has been studied, although not widely used, for the oxidation of phenols. Either radical coupling products (typical of one-electron oxidation) or quinonoid products (typical of two-electron oxidation) may be formed, depending on the reaction conditions.
Jonathan P. Kitchin
3M, St Paul, MN, USA