Britannica
Sources used in this answer
- reaction mechanism
- catalysis
- reaction mechanism - Reaction mechanisms: nature of reactants, intermediates, and products
- chemistry - Energy and the first law of thermodynamics
- reaction mechanism - The solvent
- reaction mechanism - Environmental effects
- reaction mechanism - The reaction conditions
- chemical compound - Evaluation of a synthetic method
How can reaction conditions be chosen to favor a desired reaction pathway?
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reaction mechanism
Possible energy diagram for the dissociation of a covalent molecule, E–N, into its ions E+ and N− (see text).
To favor a desired reaction pathway, chemists manipulate reaction conditions to control the energy requirements and rates of competing processes. By understanding the reaction mechanism, researchers can optimize conditions to maximize desired products while minimizing undesired ones.12
Key strategies include:
- Catalysis: Using a catalyst can selectively accelerate one reaction pathway over another, effectively excluding competing reactions.3
- Temperature: Because reactions with high energy barriers are highly responsive to temperature, increasing heat can make these pathways more likely, though it may also increase the proportion of minor products.2
- Concentration and Pressure: Higher concentrations of specific reagents favor mechanisms involving more molecules in the transition state. Similarly, increased pressure favors pathways with more closely associated transition states, as these occupy less space.2
- Solvent Choice: The solvent can influence the reaction by stabilizing the transition state relative to the initial state, particularly if there is a significant change in polarity during the reaction.45
These adjustments allow chemists to steer reactions toward kinetic or thermodynamic control, ensuring the most efficient and practical synthesis.67