They do not affect Fehling's solution and do not react with the Tollens reagent, which differentiates them from aldehydes.  
Not easily oxidized, these compounds can be synthesized by using an organolithium reagent on a nitrile, followed by hydrolysis of the product.  Useful as solvents and flavorings, they can also be made by oxidizing a secondary alcohol.  They do not affect Fehling's solution and do not react with the Tollens reagent, which differentiates them from aldehydes.  FTP, name this class of compounds with a carbonyl group between two aryl groups, the simplest of which is acetone.
Not easily oxidized, these compounds can be synthesized by using an organolithium reagent on a nitrile, followed by hydrolysis of the product.  
ketone(s)