Table 2.3 A, G, and U-Values of Cyclohexane Derivatives
ED = AR
ED = GR + GR'
ED = UR + UR' + 1/2 [AR + AR']
R or R' A (kcal/mol) G (kcal/mol) U (kcal/mol)
F 0.2 0 0
Cl 0.4 0.5 0.4
Br 0.4 0.8 0.4
I 0.4 1.0 0.4
OH, OR 0.9 0.2 0.9
NHR 1.3 0.3 1.3
NR2 2.1 0.5 2.1
N= 0.5 0.1 0.5
N≡ 0.2 0.1 1.2
C= 1.3 0.2 0.9
aryl 3.0 1.2 1.1
C≡ 0.2 0 1.2
CO2H, CO2R 1.2 0.5 1.2
CHO 0.8 0.3 0.8
CH2R 1.8 0.4 1.8
CHR2 2.1 0.8 2.1
CR3 6.0 2.5 6.0
No values are given for cis-1,2-axial-equatorial interactions because inversion leads again to a 1,2-equatorial-axial interaction. This is not the case for the trans 1,2-diequatorial isomer, since inversion affords a diaxial conformer. For conversion of kcal to kilojoules, use 1 kcal/mol = 4.184 kJ/mol.