Final answer:
The difference between thermodynamic control and kinetic control in a chemical reaction is marked by whether the most stable product is favored at equilibrium (thermodynamic) or whether the fastest forming product is favored before equilibrium is reached (kinetic). Conditions are manipulated under thermodynamic control to favor the most stable product, while kinetic control focuses on the rate of product formation.
Step-by-step explanation:
The difference between thermodynamic control and kinetic control involves how the products of a chemical reaction are determined under varying conditions. In a reaction under thermodynamic control, conditions are adjusted to favor the formation of the most stable product or set of products at equilibrium. In contrast, under kinetic control, the product distribution is determined by the rate at which different products are formed, favoring those products that are formed the fastest, regardless of their stability. Thermodynamic control is associated with the concept that a reaction mixture after sufficient time will favor the formation of the most stable product, as dictated by differences in free energy. Kinetic control, however, is concerned with the energy barriers that must be overcome to form products and often leads to a mixture of products based on their respective rates of formation, especially under conditions where the reaction is not allowed to reach equilibrium. For example, consider a simple reaction where A can turn into B or C. If B is thermodynamically more stable than C but requires more energy to form, under conditions of thermodynamic control, B will be the major product. Under kinetic control, if C forms much more rapidly than B, C may be the major product, especially if the reaction is quenched or stopped before equilibrium is reached.