Proton potential in acetylacetone

Proton potential in the medium-strong intramolecular hydrogen bond of acety lacetone is examined on various ab initio and DFT levels. Semiempirical MO methods AM1 and PM3 turn out to be inadequate for the present system. It wa s shown that the proton donor-proton acceptor distance influences the barri er height while both CO distances introduce the asymmetry to the otherwise symmetric proton potential Ab initio data are fitted to a computationally i nexpensive two-state empirical valence bond potential suitable for molecula r simulations.