Illustrated Glossary of Organic Chemistry

E1 mechanism (E1 reaction): An elimination reaction mechanism in which the three bond changes do not occur simultaneously. Carbon-leaving group bond scission occurs first, leading to a carbocation. This carbocation is then deprotonated by base to form a pi bond. An E1 reaction is never concerted.

Trisubstituted internal alkene
Major product

Disubstituted terminal alkene
Minor product
An intermolecular E1 reaction.

An intramolecular E1 reaction.