Preparation of Anhydrous Hydrogen Peroxide in Ether

5 M solution of anhydrous hydrogen peroxide in ether is prepared by repeated extraction of 30% aqueous hydrogen peroxide with ether. The ether extracts are dried over anhydrous magnesium sulfate, and the concentration of hydrogen peroxide is determined by iodometric titration. 

All the operations must be carried out with strict safety measures. 

Chromium trioxide (267 g, 2.67 mol) is dissolved in 400 mL of water, and 230 mL of concentrated sulfuric acid is added with cooling. The cold solution is diluted with water up to 1 L to form an 8 N reagent. The reagent is added dropwise to a solution of the compound to be oxidized in acetone (distilled from potassium permanganate) at 20 °C. 

The complex CrOj ZCsHsN is filtered with suction through a sintered-glass funnel, washed immediately with 300 mL of dry reagent-grade petroleum ether, and stored immediately in a desiccator over phosphorus pentoxide at 15-30 mm of Hg. The yield is 180 g (80%). The entire operation starting with the filtration should be performed within less than 3 min to minimize hydration of the extremely hygroscopic complex, which, when stored in this way, is still active after 10 days. The dry complex does not cause any fires. 

To a solution of 6 g (0.06 mol) of chromium trioxide in 11 mL of 6 N hydrochloric acid is added 4.75 g (0.06 mol) of pyridine within 10 min at 40 °C. The mixture is kept at 10 °C until a yellow-orange solid forms and then reheated to 40 °C to dissolve the solid. Alumina (50 g) is added with stirring at 40 °C. After evaporation in a rotary evaporator, the orange solid is dried in vacuo for 2 h at room temperature. The reagent can be kept under vacuum for several weeks in the dark without losing its activity. 

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