Which statement best describes the temperature dependence of an addition reaction?
A) Addition reactions are thermodynamically favored at all temperatures.
B) Addition reactions are thermodynamically disfavored at all temperatures.
C) Addition reactions are thermodynamically favored at low temperatures.
D) Addition reactions are thermodynamically favored at high temperatures.
E) Addition reactions are thermodynamically impossible.

Question

Quizplus · Accepted Answer

Addition reactions involve the breaking of π-bonds and the formation of new σ-bonds. At lower temperatures, the kinetic energy of molecules is lower, meaning that there is less energy available for the breaking of the π-bonds. Hence, the reaction rate is slower. However, the lower temperature means that the entropy change for the reaction is also lower, and since ΔG = ΔH - TΔS, the reaction becomes more thermodynamically favorable.

Which Statement Best Describes the Temperature Dependence of an Addition