Thiono

Thiono is a term used in chemistry to describe sulfur-containing analogs of oxygen-containing functional groups, particularly in organosulfur chemistry. In many contexts, thiono refers to substituting an oxygen atom in a carbonyl or related group with sulfur, producing a thiocarbonyl-type moiety. The most common instance is the thione functional group, C=S, and related derivatives that are discussed in older or specialized literature under the heading thiono compounds. The exact usage of the term varies between sources, and some scholars prefer to distinguish thione (C=S) from thio- or thiocarbonyl naming.

In nomenclature, "thiono-" may be used as a substitutive or connective element to indicate sulfur replacement for oxygen in a parent structure, leading to terms such as thionoalkyl, thionoester, or thionocarbonate in some schemes. However, thiono is not a universally standardized prefix in modern IUPAC practice, and many contemporary texts instead use explicit naming of the thiocarbonyl or sulfur-containing group.

Synthesis and occurrence: Thiono groups are typically introduced by thionation reactions, using reagents such as Lawesson's reagent or phosphorus sulfide to replace carbonyl oxygen with sulfur. Thionation is used to prepare thiocarbonyl compounds, thiones, and neighboring sulfur-containing ligands in organometallic chemistry. Thiono derivatives appear in research on polymers, dyes, and small-molecule sulfur chemistry.

See also: Thione, Thionation, Thiocarbonyl, Thionyl compounds.