A dyotropic reaction (from the Greek ''dyo'', meaning two) in organic chemistry is a type of

organic reaction Organic reactions are chemical reactions involving organic compounds. The basic organic chemistry reaction types are addition reactions, elimination reactions, substitution reactions, pericyclic reactions, rearrangement reactions, Mechanistic Organ ...

and more specifically a pericyclic

valence isomerization In organic chemistry, two molecules are valence isomers when they are constitutional isomers that can interconvert through pericyclic reactions. Benzene There are many valence isomers one can draw for the C6H6 formula benzene. Some were originally ...

in which two sigma bonds simultaneously migrate intramolecularly. The reaction type is of some relevance to organic chemistry because it can explain how certain reactions occur and because it is a synthetic tool in the synthesis of organic molecules for example in total synthesis. It was first described by

Manfred T. Reetz Manfred Theodor Reetz (born 13 August 1943) is a German chemist and professor of organic chemistry, who served as director of the Max Planck Institute for Coal Research from 1991 until 2011. His research focuses on directed evolution, enzymes in o ...

in 1971 In a type I reaction two migrating groups interchange their relative positions and a type II reaction involves migration to new bonding sites without positional interchange.

Type I rearrangements

In type I rearrangements (Y-A-B-X conversion to X-A-B-Y) the two migrating groups are oriented trans to each other and as a result of the rearrangement they migrate to opposite sides. The first example of a dyotropic rearrangement involving a carbon-carbon bond was reported by Cyril A. Grob and Saul Winstein. They observed the interconversion of 2 bromine atoms in a certain

steroid A steroid is a biologically active organic compound with four rings arranged in a specific molecular configuration. Steroids have two principal biological functions: as important components of cell membranes that alter membrane fluidity; and a ...

. In a straightforward example the two bromine atoms in 3- tert-butyl-trans-1,2-dibromohexane mutarotate by heating. In the transition state both bromine atoms connect symmetrically to both carbon atoms on opposite sides and the reaction is

concerted In chemistry, a concerted reaction is a chemical reaction in which all bond breaking and bond making occurs in a single step. Reactive intermediates or other unstable high energy intermediates are not involved. Concerted reaction rates tend not ...

. Stepwise mechanisms in dyotropic reactions have also been investigated. : Dyotropic reaction Barili 1970

In organic synthesis an important application is the conversion of 4-substituted-gamma- lactones to

butyrolactone Butyrolactone may refer to: * ''beta''-Butyrolactone * ''gamma''-Butyrolactone (GBL) {{Short pages monitor