Leaving group
(LG; nucleofuge): An atom or group
of atoms which breaks away from the rest of the molecule,
taking with it the electron pair which used to be the bond
between the leaving group
and the rest of the molecule.
The bond
scission occurs via heterolytic
bond
cleavage. A leaving group
which departs from a proton
is usually referred to as the conjugate
base of the corresponding acid.
Even though 'group'
refers to two or more atoms bonded
together, a leaving group
composed of a single atom (such as Br-)
it is still called a leaving group.
