Ei mechanism

An elimination pathway in which bond breaking and bond formation occur together through a cyclic transition state, without a discrete ionic intermediate.

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Syn elimination: An elimination in which the departing groups leave from the same face of a molecule. Ei reactions are a concerted syn-elimination subtype.
Elimination reaction: A reaction that removes atoms or groups from a molecule, usually forming a multiple bond. Ei is one mechanistic route to an elimination product.
E2 reaction: A concerted β-elimination usually requiring an anti-periplanar arrangement of the departing groups. E2 is concerted like Ei but typically follows anti rather than syn geometry.
Cope elimination: A thermal syn elimination of a tertiary amine oxide that produces an alkene and a hydroxylamine. It is a classic example of an Ei pathway through a cyclic transition state.
Cyclic transition state: A transition-state arrangement in which reacting atoms form a closed ring of partial bonds. The cyclic arrangement coordinates bond cleavage and formation in Ei reactions.
Alkene: A hydrocarbon containing at least one carbon–carbon double bond. Ei commonly forms an alkene by removing neighboring substituents.
E1 reaction: A two-step elimination that forms a carbocation before loss of a proton. E1 proceeds through a discrete ionic intermediate absent from Ei.
Chugaev elimination: A thermal syn elimination of a xanthate ester that produces an alkene and carbonyl sulfide. Its intramolecular proton transfer and cyclic transition state illustrate Ei chemistry.
Stereospecific reaction: A reaction whose stereochemical outcome is determined by the stereochemistry of its reactants. The required syn geometry makes substrate stereochemistry shape the Ei product.
Leaving group: An atom or group that departs with the bonding electron pair during a reaction. Its departure is one of the coordinated events in Ei elimination.