A chemist studies the conversion of liquid cyclohexanol to liquid cyclohexanone at 298 K

CHEMISTRY · Multi-part · AP · Chemistry · Kinetics · Kinetics

Problem

A chemist studies the conversion of liquid cyclohexanol to liquid cyclohexanone at 298 K. Calorimetric measurements show that the reaction releases 75 kJ mol−175\,\text{kJ\,mol}^{-1} of heat. Kinetic experiments give the following activation energies for the rate-determining elementary step. • Without catalyst: Ea=150 kJ mol−1E_{a}=150\,\text{kJ\,mol}^{-1} • With a cobalt(III) complex catalyst: Ea=60 kJ mol−1E_{a}=60\,\text{kJ\,mol}^{-1} Answer the following. (a) Sketch a qualitative potential-energy diagram (energy on the vertical axis, reaction progress on the horizontal axis) that shows both the catalyzed and uncatalyzed reaction pathways on the same set of axes. Label the following clearly on your sketch: reactants, products, EaE_{a} (both pathways), and ΔH\Delta H. No numerical scale is required. (b) Explain, in terms of potential-energy changes for the species involved, why the value of ΔH\Delta H is identical for the catalyzed and uncatalyzed pathways even though their activation energies differ dramatically. (c) The cobalt(III) complex operates by forming a short-lived alcoholate intermediate. Describe how the presence of such an intermediate would be reflected in the shape of the catalyzed energy curve you drew in part (a).

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