A type of reaction in which radicals are exchanged. In inorganic chemistry, it is also called double decomposition. A simple example is KCL+AgNO3 → KNO3+AgCl. Metathesis of alkenes is an important type of reaction in synthetic organic chemistry. It involves exchange of groups. For example RHC=CH2+RHC=CH2 → RHC=CHR+H2C=CH2. Reactions of this type are catalysed by metal alkylides (containing an M=CR2 grouping) and the intermediate is a four-membered ring containing the metal ion. The catalysts most often used are the Schrock catalysts based on molybdenum and the Grubbs catalysts based on ruthenium. The American chemists Richard Schrock and Robert Grubbs shared the Nobel prize for chemistry in 2005 for work in this field.
KCL+AgNO3 → KNO3+AgCl.
RHC=CH2+RHC=CH2 → RHC=CHR+H2C=CH2.