The
E1cB elimination reaction is a type of
elimination reaction which occurs under basic conditions, where a particularly poor
leaving group (such as -OH or -OR) and an acidic hydrogen eliminate to form an additional bond. E1cB is a two-step process. First, a
base abstracts the most acidic proton to generate a stabilized
anion. The lone pair of electrons on the anion then moves to the neighboring atom, thus expelling the leaving group and forming
double or
triple bond. The name of the mechanism -
E1cB - stands for
Elimination
Unimolecular
conjugate
Base.
Elimination refers to the fact that the mechanism is an
elimination reaction and will lose two substituents.
Unimolecular refers to how this reaction only involves one
molecular entity. Finally,
conjugate base refers to the formation of the carbanion
intermediate, which is the conjugate base of the starting material.