What does a reaction mechanism describe?

A reaction mechanism provides a detailed account of how a chemical reaction occurs at the molecular level. Specifically, it outlines the step-by-step sequence of elementary reactions that lead to the overall transformation of reactants into products. Each elementary reaction describes a specific event, such as the breaking of bonds, formation of intermediates, and transitions to the final products.

This sequential description is critical because it helps chemists understand the pathway of a reaction, identify intermediates, and predict reaction behavior under various conditions. By focusing on the individual steps, a mechanism can also point to the rate-determining step, which is the slowest step that governs the overall reaction rate.

The other options highlight aspects of chemical reactions but do not capture the essence of what a reaction mechanism truly represents. For instance, while analyzing reaction rates is important in kinetics, it does not involve the detailed process provided by the mechanism. Similarly, knowing the final products or the concentrations of reactants and products at equilibrium pertains to different areas of chemical study and does not explain the intricacies of how a reaction unfolds.