Curtin–Hammett principle

The Curtin - Hammett principle is one erected by David Yarrow Curtin and Louis Plack Hammett principle in chemical kinetics. It states that in a chemical reaction, the position of an upstream fast equilibrium does not affect the product formation. If two reactive intermediates A and B are in equilibrium (for example, conformers ) and, one of these intermediates ( A) in a product C and the other ( B) pass into D, the product ratio depends only on the free energy of the transition state for each product, but does not depend on the equilibrium constant K is between a and b. A and B are in dynamic equilibrium, A is transformed irreversibly into C, B to D irreversible.

K is the equilibrium constant between A and B, k1 and k2, are the rate constants for the formation of C and D, respectively, the reaction rate of the conversion of A to B and vice versa is greater than K1 or K2, means the Curtin Hammett principle that the product ratio C: D does not depend on K but by the relative energies of the transition states.

The power scheme can be represented as follows:

The product ratio depends only on ΔΔG ‡ (see scheme ): C is the main product, because the energy of the transition state TS1 is lower than that of the state TS2. It does not matter if is in equilibrium more of A or B.

• Kinetics (chemistry)