Description of the Tautomerism in Some Azonaphthols

作者：Kawauchi Susumu; Antonov Liudmil^*

来源：Journal of Physical Organic Chemistry, 2013, 26(8): 643-652.

DOI：10.1002/poc.3143

• azonaphthols
• tautomeric equilibrium
• quantum-chemical calculations
• model tautomers
• DFT

The performance of several functionals (M06-2X, B97D, B97 family and B2PLYPD), accounting long range correlation, was evaluated in respect of the tautomerism of 1-phenylazo-4-naphthol. Three sets of experimental data were used to define the evaluation criteria: reproduction of the bond lengths in the structures of the individual tautomers, description of the non-planarity of the enol tautomer and prediction of the position of the tautomeric equilibrium (G value) at 298K. The results show that M06-2X at most of the basis sets reasonably covers all requirements. In most of the cases, the empirical dispersion correction tends to stabilize the keto tautomer independently on the basis set. The obtained results have been used to select M06-2X, B97X and B2PLYP functionals to test their performance for a set of azonaphthols (1-phenylazo-4-napthol, 1-phenylazo-2-naphthol and 2-phenylazo-1-naphthol) where experimental data for the Gibbs free energies at room temperature are available. As a result, it should be pointed out the M06-2X functional slightly overestimates the enol tautomer, but at 6-31G**, TZVP and def2TZVP basis sets, the deviation is below 0.5 kcal.mol-1. The same result, but in favor of the keto tautomer, is obtained at B2PLYP/D95++**.

• 出版日期2013-8