In organic chemistry, thioketones (from Ancient Greek θεῖον (theion) 'sulfur';[1] also known as thiones or thiocarbonyls) are organosulfur compounds related to conventional ketones in which the oxygen has been replaced by a sulfur.[2] Instead of a structure of R2C=O, thioketones have the structure R2C=S, which is reflected by the prefix "thio-" in the name of the functional group. Thus the simplest thioketone is thioacetone, the sulfur analog of acetone. Unhindered alkylthioketones typically tend to form polymers or rings.[3][4]