# What are leaving groups in nucleophilic substitution reactions?

Jan 7, 2015

The leaving group is the part of the substrate that is missing at the end of the reaction.

The equation for a typical nucleophilic substitution reaction is

Nu⁻ + R-L → Nu-R + L⁻

Nu⁻ is the nucleophile, and R-L is the substrate.

The L group is missing from the substrate, so L is the leaving group.