metathesis

Metathesis is a term used in both linguistics and chemistry to describe rearrangement processes, though the two domains refer to different phenomena. In linguistics, metathesis is the transposition of sounds or syllables within a word or between adjacent words. In chemistry, it describes a rearrangement of bond partners in reactions, yielding new product combinations.

In languages, metathesis can be a historical sound change (a diachronic process) or a real-time speech error (a synchronic phenomenon). It may occur within a word or across morpheme boundaries, and some languages display productive metathesis as part of their phonology. A well-known English example is the pronunciation of “ask” as “aks” in certain dialects. Spoonerisms—swapping sounds across words in phrases—are related forms observed in speech errors as well.

In chemistry, metathesis reactions involve the exchange of substituents between reacting species, often summarized as AB + CD → AD + CB. These reactions are common in inorganic and organic chemistry and include precipitation and acid–base reactions as well as classic double-displacement processes. In organometallic and synthetic chemistry, olefin metathesis rearranges carbon–carbon double bonds and is catalyzed by metal complexes. Major variants include ring-opening metathesis polymerization (ROMP), ring-closing metathesis (RCM), and cross metathesis (CM).

The concept provides a unifying label across fields for processes that switch partners or order, and olefin metathesis in particular has had a substantial impact on modern chemical synthesis. In 2005, Yves Chauvin, Robert H. Grubbs, and Richard R. Schrock were awarded the Nobel Prize in Chemistry for work related to metathesis chemistry.