Assertion (A): When two conformers interconvert much faster than they react, the product ratio generally differs from the equilibrium ratio of the conformers. Reason (R): The product ratio is governed by the difference in free energy of the two transition states.

ABoth A and R are true and R is the correct explanation of A
BBoth A and R are true but R is not the correct explanation of A
CA is true but R is false
DA is false but R is true

Answer: A

This is the Curtin-Hammett principle. The conformers stay in equilibrium, so the rate to each product depends on the free energy of its transition state relative to the common pool. Thus the ratio is set by the transition-state energy gap, not by the conformer populations. A and R are true and R explains A.

Practice General Organic Chemistry III: Reaction Intermediates More on Reaction energy profiles, kinetic vs thermodynamic control

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Assertion (A): When two conformers interconvert much faster than they react, the product ratio generally differs from the equilibrium ratio of the conformers. Reason (R): The product ratio is governed by the difference in free energy of the two transition states.

Answer: A

More questions on Reaction energy profiles, kinetic vs thermodynamic control