page_title: Benzophenone
section_title: Benzophenone radical anion
hierarchical_section_title: Benzophenone / Organic chemistry / Benzophenone radical anion
caption_attribution_description: Solvent pot
context_page_description: Benzophenone is the organic compound with the formula (C₆H₅)₂CO, generally abbreviated Ph₂CO. It is a white solid that is soluble in organic solvents. Benzophenone is a widely used building block in organic chemistry, being the parent diarylketone.
context_section_description: Alkali metals reduce benzophenone to the deeply blue colored radical anion, diphenylketyl:
  M  +  Ph₂CO   →   M⁺Ph₂CO•-
  Generally sodium is used as the alkali metal. Although inferior in terms of safety and effectiveness relative to molecular sieves, this ketyl is used in the purification of organic solvents, particularly ethers, because it reacts with water and oxygen to give non-volatile products. The ketyl is soluble in the organic solvent being dried, so it accelerates the reaction of the sodium with water and oxygen. In comparison, sodium is insoluble, and its heterogeneous reaction is much slower. When excess alkali metal is present a second reduction may occur, resulting in a color transformation from deep blue to purple:
  M  +  M⁺Ph₂CO•-   →   (M⁺)₂(Ph₂CO)²⁻
caption: A solvent pot containing dibutyl ether solution of sodium benzophenone ketyl, which gives it its purple color.
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