Computational investigation of the substituent effect on the intramolecular proton transfer reaction of 3-hydroxytropolone

The effects of substituent type and position on the proton transfer reaction of 3-hydroxytropolone (3-OHTRN) have been investigated theoretically by using density functional theory at the level of B3LYP/ 6-31+G?? method. The influence of solvent on the proton transfer reactions of substituted 3-OHTRN has been examined using the self-consistent isodensity polarized continuum model (SCI-PCM) in water. As a result, while the proton transfer reaction is kinetically the easiest by substitution on position 3 of -NH2 group in the gas phase, it is kinetically the easiest by substitution on position 5 of the same group in water. In addition, these reactions are either kinetically or thermodynamically easier in the gas phase than that in water, except the reaction of structure with -NH2 group at position 6.