I am relatively new and interested in the field of theoretical chemistry. I just stumbled across the Klopman - Salem equation (https://en.wikipedia.org/wiki/Klopman-Salem_equation).

In daily life, I only use DFT for bonding energies and I also do not find too many papers about the Klopman - Salem equation, why?

What are the advantages and disadvantages of this theory? Are there any theories, that improved this concept?


1 Answer 1


Although its importance from a "conceptual" point of view (it justifies both the frontier orbitals theory and the hard and soft acids and bases theory) this equation is very rarely used in theoretical calculations because it comes out from multiple approximations (i.e. rigid molecules, Hammond's postulate, no solvent contribution, no entropic contribution to the transition state) and its simplicity in terms of computational weight doesn't overcome its scarce accuracy.


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