Elimination reaction

An elimination reaction removes atoms or groups from a molecule, usually forming a multiple bond between adjacent atoms. In organic chemistry, it commonly converts a saturated molecule into an alkene or alkyne.

E2 reaction: A concerted elimination in which a base removes a proton as a leaving group departs. This one-step pathway is a common route from alkyl halides to alkenes.
Leaving group: An atom or group that departs with the bonding electron pair during a reaction. Elimination requires a group to leave as a new bond forms.
Nucleophilic substitution: A reaction in which a nucleophile replaces a leaving group on an electrophilic atom. It competes with elimination when nucleophiles and alkyl substrates react.
Alkene: A hydrocarbon containing at least one carbon–carbon double bond. Alkenes are the usual products when elimination removes groups from adjacent saturated carbons.
E1 reaction: A two-step elimination that forms a carbocation before loss of a proton. Its carbocation intermediate explains rearrangements and competition with substitution.
Brønsted–Lowry acid–base theory: A theory in which acids donate protons and bases accept protons. Many eliminations begin when a base removes a proton from the substrate.
SN1 reaction: A two-step nucleophilic substitution that proceeds through a carbocation intermediate. Like E1, it forms a carbocation, but a nucleophile attacks instead of a proton being lost.
Alkyne: A hydrocarbon containing at least one carbon–carbon triple bond. Strong-base elimination of suitable dihalides can produce an alkyne.
E1cB reaction: A two-step elimination that forms a carbanion before a leaving group departs. This pathway occurs when proton removal is favorable but the leaving group is poor.
Beta carbon: A carbon atom one bond away from a reference atom or functional group. The proton removed in common alkene-forming eliminations is attached to a beta carbon.

Linked from 16 pages