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How can a chemical reaction follow more than one pathway to produce different products?

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dissociation of E–N — reaction mechanism Possible energy diagram for the dissociation of a covalent molecule, E–N, into its ions E⁺ and N⁻ (see text).

Chemical reactions can follow multiple pathways because they are often complex, multi-stage processes where the starting materials can traverse different energy surfaces to reach various products.12

The specific course a reaction takes is determined by the energy requirements of the system. Molecules must overcome an energy barrier to reach a transition state; the pathway that requires the least activation energy is typically favored. However, when multiple products are possible, a reaction may be governed by either kinetic control or thermodynamic control.123

Kinetic control: The reaction proceeds along the path that forms products most rapidly, often yielding the thermodynamically less stable product.3
Thermodynamic control: The reaction allows for reversibility, eventually shifting the product distribution toward the most stable (equilibrium) state.3

Chemists study these mechanisms to understand how to manipulate reaction conditions—such as temperature or the choice of solvent—to favor one pathway over another, thereby maximizing the yield of desired products while minimizing undesired ones. The existence of competing reactions and intermediate complexes further allows for diverse outcomes depending on the specific reaction environment.12