A ketyl group in organic chemistry is an anion radical that contains a group RCO. It is the product of the 1-electron reduction of a ketone.  
Another mesomeric structure has the radical position on carbon and the negative charge on oxygen. 
Ketyls can be formed as radical anions by one-electron reduction of carbonyls with alkali metals. Sodium and potassium metal reduce benzophenone in THF solution to the soluble ketyl radical. Ketyls are also invoked as intermediates in the pinacol coupling reaction.