Osmic acid peroxide

Osmium tetroxide (0s04, sometimes called osmic acid) reacts with alkenes in a concerted step to form a cyclic osmate ester. Oxidizing agents such as hydrogen peroxide (H202) or tertiary amine oxides (R3N+—O-) are used to hydrolyze the osmate ester and reoxidize osmium to osmium tetroxide. The regenerated osmium tetroxide catalyst continues to hydroxylate more molecules of the alkene. [Pg.364]

Procedure Transfer an accurately measured volume of sample, equivalent to about 25 mg of diacetyl, into a suitable flask. Add 3 drops of phenolphthalein TS, and neutralize the acidity by titrating with 0.05 N sodium hydroxide to a faint pink endpoint. Add 0.25 mL of 30% hydrogen peroxide solution and 3 drops of 0.01% Osmic Acid. Mix, cover the flask, and allow it to stand in an incubator held at about 38° for not less than 4 h. Cool to room temperature, and titrate with 0.05 N sodium hydroxide to a faint pink endpoint. Each milliliter of 0.05 N sodium hydroxide is equivalent to 8.6 mg of diacetyl. [Pg.450]

Transition metal catalysts not only increase the reaction rate but may also affect the outcome of the oxidation, especially the stereochemistry of the products. Whereas hydrogen peroxide alone in acetonitrile oxidizes alkenes to epoxides [729], osmic acid catalyzes syn hydroxylation [736], and tungstic acid catalyzes anti hydroxylation [737]. The most frequently used catalysts are titanium trichloride [732], vanadium pentoxide [733,134], sodium vanadate [735], selenium dioxide [725], chromium trioxide [134], ammonium molybdate [736], tungsten trioxide [737], tungstic acid [737],... [Pg.7]

OSMIC ACID (20816-12-0) Contact with hydrochloric acid produces chlorine gas. Explosive reaction with 1-methylimidazole. Violent reaction with hydrogen peroxide. Contact with organic and combustible materials may cause fire and explosions. [Pg.900]