Production, Structure, and Basic Reactions
Chromium trioxide is generated by treating sodium chromate or the corresponding sodium dichromate with sulfuric acid:
- H2SO4 + Na2Cr2O7 → CrO3 + Na2SO4 + H2O
Approximately 100M kg are produced annually by this or similar routes.
The solid consists of chains of tetrahedrally coordinated chromium atoms that share vertices. Each chromium center, therefore, shares two oxygen centers with neighbors. Two oxygen atoms are not shared, giving an overall stoichiometry of 1:3.
The structure of monomeric CrO3 has been calculated using density functional theory, and is predicted to be pyramidal (point group C3v) rather than planar (point group D3h).
Chromium trioxide decomposes above 197 °C liberating oxygen eventually giving Cr2O3:
- 4 CrO3 → 2 Cr2O3 + 3 O2
It is used in organic synthesis as an oxidant, often as a solution in acetic acid, or acetone in the case of the Jones oxidation. In these oxidations, the Cr(VI) converts 1.5 equivalents of alcohols to the corresponding ketones or carboxylic acids:
- 2 CrO3 + 3 RCH2OH → Cr2O3 + 3 RCOOH + 3 H2O
Read more about this topic: Chromium Trioxide
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