An ab initio study of the structure and intramolecular proton transfer in tropolone

An ab initio study of tropolone was carried out at the 3-21G level, with full optimization of the geometry, and the intramolecular proton transfer in the ground state was analysed. The two equivalent Cs structures can be converted to each other via a C2v symmetry transition state with a double minimum potential. The splitting of the ground vibrational state generated by proton tunneling was determined by procedures of variable complexity and found to be in the range Δ = 0.1–0.15 cm−1, i.e., clearly smaller than experimental predictions. Key words: tropolone, intramolecular hydrogen bond, proton transfer, ab initio calculations, molecular structure.