In organic chemistry, the basic types of reactions can be classified as:
Addition reactions, where two or more substances combine to form a more complex molecule;
Substitution reactions, where one atom or group of atoms in a molecule is replaced by another atom or group;
Elimination reactions, which involve the removal of a small molecule from a larger one, often yielding an unsaturated molecule;
Rearrangement reactions, where the molecular structure changes through the redistribution of atoms within the molecule.