CrO3

CrO3, also called chromium trioxide or chromic anhydride, is an inorganic compound with the formula CrO3. It appears as a bright orange to red crystalline solid. It is highly hygroscopic and readily absorbs water from the air. In water, CrO3 converts to chromic acid (H2CrO4), and aqueous solutions contain chromate species depending on pH.

CrO3 contains chromium in the +6 oxidation state. It is a powerful oxidizing agent and reacts vigorously with reducing substances. It is widely used as an oxidant in organic synthesis, most notably in Jones oxidation, where primary alcohols are oxidized to carboxylic acids and secondary alcohols to ketones. Industrially, it is also a component in chromium plating baths and in the production of chromic acid solutions for surface finishing.

Preparation of CrO3 typically involves dehydration of chromic acid solutions, for example by heating aqueous H2CrO4 to remove water, yielding solid CrO3. Because of its hygroscopic and reactive nature, CrO3 must be handled with appropriate safety measures in place to prevent exposure.

Safety and handling: CrO3 is toxic, corrosive, and a strong oxidizer. Hexavalent chromium compounds are both toxic and carcinogenic, and exposure should be minimized. Inhalation of dust or fumes can irritate the respiratory tract; skin and eye contact can cause burns. Usage requires proper engineering controls, protective equipment, and secure disposal in accordance with regulatory requirements.

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