Table 4.

The zero-point total energy (ΔE/kJ·mol⁻¹), enthalpy (ΔH/kJ·mol⁻¹), free energy (ΔG/kJ·mol⁻¹) and entropy (ΔS/J·mol⁻¹·K⁻¹) changes and equilibrium constant (K) for the tautomerization reaction: 2-PY↔2-HPY at 298.15 K.

Level of Theory	ΔE	ΔH°	ΔG°	ΔS°	K
B3LYP/6-311++G**	52.72	50.32	58.56	−27.632	3.648
B3LYP/aug-cc-pvdz	10.416	8.576	15.632	−23.664	10.784
CAM-B3LYP/6-311++G**	12.096	9.536	18.192	−29.04	10.112
CAM-B3LYP/aug-cc-pvdz	−31.808	−33.648	−26.464	−24.096	31.168
M062X/6-311++G**	−102.496	−105.312	−95.952	−31.392	179.76
M062X/aug-cc-pvdz	−143.92	−145.936	−138.368	−25.376	524.048
ωB97XD/6-311++G**	42.928	40.288	49.152	−29.728	4.64
ωB97XD/aug-cc-pvdz	−4.16	−6.224	1.344	−25.376	15.472
CCSD/6-311++G**	−77.296	−92.288	−50.16	−141.296	56.688
CCSD/aug-cc-pvdz	−81.2	−83.808	−74.352	−31.712	104.336