ArSAr

ArSAr denotes a diaryl sulfide, a type of thioether in organic chemistry. The general structure is Ar–S–Ar, where Ar represents an aryl group. The two aryl rings may be identical (e.g., diphenyl sulfide) or different (mixed diaryl sulfides). Diaryl sulfides are typically relatively stable compounds and are often liquids or solids at room temperature with odor characteristics that depend on the substituents on the rings.

Structure and properties: In Ar–S–Ar, sulfur is divalent and bonded to two sp2 carbon centers. The C–S–C angle is typically wide due to the lone pair on sulfur, and C–S bond lengths are around 1.8 Å. Substituents on the aryl rings influence polarity, boiling point, and reactivity. Diaryl sulfides are less reactive toward oxidation than thiols, but they can be oxidized to sulfoxides (Ar–S(O)–Ar) and further to sulfones (Ar–SO2–Ar) with appropriate oxidants.

Synthesis: The most common preparation is a C–S cross-coupling between an aryl halide (Ar–X) and a thiol (Ar'–SH) under base and copper- or palladium-catalysis to furnish Ar–S–Ar'. Other routes include coupling of thiols with aryl electrophiles under Ullmann-type conditions or using aryl sulfenyl chlorides in suitable reaction media.

Applications: Diaryl sulfides serve as fragrance components and odorants, due to their characteristic scents. They are also used as ligands in homogeneous catalysis and as intermediates in the synthesis of pharmaceuticals and agrochemicals. Related compounds include polysulfides and dibenzothiophene derivatives.

See also: diphenyl sulfide, thioether, sulfoxide, sulfone.