Kinetic versus Thermodynamic Control of Product Distribution. At higher temperatures the 1,4-addition product predominates. The product distribution produced at the lower temperature will gradually equilibrate to the product distribution at the higher temperature if allowed to warm. Related to Ea of the slow step in each case. Occurs at the lower temperature.
Products interconvert until some equilibrium mixture is obtained.
Occurs at the higher temperature. Energy Diagram 5. In many cases the 1,4-product is the thermodynamically favored, but no always.