Fig. 3: Tautomeric forms of cyclic triketones and the trends in bond length variation with pKa for compounds labelled tkn and tkc in this work.
From: Aqueous pKa prediction for tautomerizable compounds using equilibrium bond lengths
a Tautomeric forms a–d considered for the triketone series tkn1-tkn4 and tkc1-tkc6. All energies are listed in Supplementary Table 6 of the SI. b The trend in bond length variation and exchange-correlation (Vxc) energy of bonding interactions for tkn1-tkn4 is consistent with delocalization of electrons across the whole endocyclic keto-enol fragment. Conversely, the variation in bond lengths for tkc1-tkc6, as well as the increased co-planarity of the keto-enol group, is indicative that there is more conjugation with the exo-carbonyl. Supplementary Table 7 of the SI lists bond lengths i–v and pKa values for the b tautomer.
