Table 2.

Relative free energies for the conformers/tautomers of the isoxazole and isothiazole OH derivatives. Energies in kJ/mol relative to the corresponding cis OH species ^a.

	Gas	CH2Cl2			Water
	ΔGgint	ΔGsint	ΔGsolv	ΔGstot	ΔGsint	ΔGsolv	ΔGstot
3OH isoxazole
3OH, trans	13.5	17.9	−12.7	5.2	20.1	−17.2	2.9
3-one, NH	4.6 b	9.8	−11.2	−3.1 b	11.3	−14.3	−4.7 b
3OH isothiazole
3OH, trans	14.9	19.3	−12.9	6.4	21.6	−17.5	4.1
3-one, NH	4.6	13.6	−19.2	−5.6	16.4	−24.7	−8.2
4OH isoxazole
4OH, trans	0.0	0.1	−0.2	−0.1	0.1	−0.2	−0.1
4-one, C5H	1.9	−0.6	6.6	6.0	−1.6	9.2	7.6
4OH isothiazole
4OH, trans	−0.4	0.8	−1.1	−0.3	1.0	−1.6	−0.6
4-one, C5H	12.9	12.7	3.3	15.9	12.3	4.8	17.1

^a See the footnote of Table 1; ^b –RT ln 2 = –1.71 kJ/mol is included for the entropy of mixing of the optical antipodes with C₁ symmetry.