Thermodynamic and Kinetic Control Practice Test

In a synthesis, reactant S can form two products, A and B, via two competing pathways.

Textual energy-profile description (no numerical values):

• The pathway to A has a higher activation energy than the pathway to B.
• Product A is lower in energy (more stable) than product B.

The reaction is carried out at high temperature for a long time in a closed system, allowing the mixture to approach equilibrium.

Which statement best describes the favored product and control under these conditions?

A student studies the addition of HBr to an unsymmetrical conjugated diene. Two products can form: Product X (the 1,2-addition product) and Product Y (the 1,4-addition product). A reaction energy profile (not shown) indicates that the pathway to X has the lower activation energy, while Y is the lower-energy (more stable) product. If the reaction is run at low temperature for a short time and then quenched, which outcome is most likely?