Chromium(VI) Oxide-Silica Gel


[1333-82-0]  · CrO3  · Chromium(VI) Oxide-Silica Gel  · (MW 99.99) (SiO2)

[60676-86-0]  · O2Si  · Chromium(VI) Oxide-Silica Gel  · (MW 60.09)

(reagent for oxidizing alcohols to carbonyl compounds)

Physical Data: CrO3 mp 196 °C; d 2.70 g cm-3.

Preparative Methods: the reagent is prepared by addition of silica gel to an aqueous solution of chromium(VI) anhydride.1

Handling, Storage, and Precautions: can be stored under vacuum in the dark and must be used within one week. Chromium(VI) anhydride is a highly toxic cancer suspect agent. All chromium(VI) reagents must be handled in a fume hood. The mutagenicity of CrVI compounds is well documented.2

Oxidation of Alcohols to Carbonyl Compounds.

Chromium(VI) anhydride-silica gel oxidizes alcohols to carbonyl compounds in good yields (eqs 1-3).1 The (S)-alcohol (1) is oxidized to the aldehyde (2) by chromium(VI) anhydride-silica gel with 22% racemization (eq 2).3 The Collins reagent (Dipyridine Chromium(VI) Oxide) gives only 5% racemization. Variations of this reagent include Sodium Dichromate containing Sulfuric Acid on silica gel, and pyridinium chromate on silica gel.4 The former reagent is active after one year's storage under ordinary conditions.

Related Reagents.

In addition to sodium dichromate containing sulfuric acid on silica gel and pyridinium chromate on silica gel,4 Chromyl Chloride on silica-alumina,5 Pyridinium Chlorochromate-Alumina,6 Chromic Acid on graphite,7 chromic acid adsorbed on Kieselguhr,8 and chromic acid attached to an anion exchange resin9 are also valuable for oxidizing alcohols to carbonyl compounds. Chromic acid on graphite selectively oxidizes primary alcohols in the presence of secondary and tertiary alcohols.7

1. Santaniello, E.; Ponti, F.; Manzocchi, A. S 1978, 534.
2. Cupo, D. Y.; Wetterhahn, K. E. Cancer Res. 1985, 45, 1146.
3. Evans, D. A.; Bartroli, J. TL 1982, 23, 807.
4. Singh, R. P.; Subbarao, H. N.; Dev, S. T 1979, 35, 1789.
5. San Filippo, J., Jr.; Chern, C.-I. JOC 1977, 42, 2182.
6. Cheng, Y.-S.; Liu, W.-L.; Chen, S.-H. S 1980, 223.
7. Lalancette, J.-M.; Rollin, G.; Dumas, P. CJC 1972, 50, 3058.
8. Lou, J.-D. SC 1989, 19, 1841.
9. Cainelli, G.; Cardillo, G.; Orena, M.; Sandri, S. JACS 1976, 98, 6737.

Fillmore Freeman

University of California, Irvine, CA, USA

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