Question #44178

Consider the keto-enol (di-lactam $\rightleftharpoons$ di-lactim) tautomerization of Uracil (\ce{C4H4N2O2}) at 298 K. In the gas phase, the di-lactam form is favored by $\Delta G^\circ \approx +50 \text{ kJ mol}^{-1}$. In an aqueous solvent, this energy gap decreases drastically. Consider the following statements regarding the thermodynamic drivers and structural changes during the transition from the di-lactam to the di-lactim form:

I. The di-lactim form possesses a lower sum of localized bond enthalpies due to the weaker exocyclic $C-O$ bonds compared to the $C=O$ bonds in the di-lactam form. II. The $C_4-N_3$ bond length increases in the di-lactim form because aromatic delocalization reduces the formal $C=N$ double bond character. III. The relative stabilization of the di-lactim form in water is synergistically driven by its $6\pi$ aromatic resonance energy and a highly exothermic hydration enthalpy ($\Delta H_{hyd}$). IV. The exocyclic carbon-oxygen bond length decreases during the tautomerization due to the formation of strong hydrogen bonds with water.

Which of the above statements are CORRECT?