WHAT ARE SUBSTITUION REACTIONS AND HOW THEY GET REACT?
Substitution reaction, any of a class of chemical reactions in which an atom, ion, or group of atoms or ions in a molecule is replaced by another atom, ion, or group. An example is the reaction in which the chlorine atom in the chloromethane molecule is displaced by the hydroxide ion, forming methanol:
CH3Cl + ?OH? CH3OH + Cl-