Thioketone

Thioketone, or thiocarbonyl compound, is an organic molecule containing a thiocarbonyl group (R-C(=S)-R'), the sulfur analog of a ketone carbonyl. In this class, the oxygen of the carbonyl is replaced by sulfur. If one substituent on the carbonyl carbon is hydrogen, the substance is a thioaldehyde rather than a thioketone.

Preparation of thioketones is commonly achieved by thionation of ketones using specialized reagents such as Lawesson’s reagent or phosphorus pentasulfide (P4S10). These agents convert a carbonyl compound into the corresponding thioketone. Other approaches include conversions of acyl chlorides or esters to thione derivatives under sulfur-transfer conditions.

Notable examples include thiobenzophenone (diphenyl thioketone) and 9-thioxanthone, a well-known photoinitiator in polymer chemistry. Many thioketones are stable enough to isolate, especially when aryl groups flank the thiocarbonyl center, while others are reactive and used as intermediates in synthesis.

Reactivity and properties of thioketones follow their thiocarbonyl character. The C=S bond is polarizable and serves as a locus for nucleophilic attack at carbon, enabling additions and various cycloaddition reactions. The sulfur atom also imparts distinct photochemical and electronic properties, making thioketones valuable in UV-visible chemistry and materials science. Their applications include serving as synthetic intermediates to sulfur-containing derivatives and as photoinitiators or sensitizers in light-driven processes.