Conformational Energies (A-Values)

Group A-Value (kcal/mol) Group A-Value (kcal/mol)
Me 1.70 Et 1.75
CF3 2.1 CH=CH2 1.35 (1.68)8
CN 0.17 (0.21)9 CC-H 0.41 (0.52)9
CH2CMe3 2.0 CH2OTs 1.75
i-Pr 2.15 c-Hexyl 2.15
t-Bu >4.5 Ph 3.0
CO2-* 1.92 CO2H* 1.35
CO2Me 1.27 CO2iPr 1.20
C(=O)H 0.8 C(=O)Cl 1.25
C(=O)Me 1.17 - -
D 0.0081 T 0.011
F 0.15 (0.36)9 Cl 0.43 (0.51)9
Br 0.38 (0.49)9 I 0.43 (0.49)9
O-Me 0.60 (0.75)9 O-CD3 0.56
O-Et 0.9 O-H* 0.87 (1.0)9
O-Ac 0.6 (0.79)9 O-C(=O)CF3 0.68 (0.58)9
O-CHO 0.27 (0.62)9 O-Ts 0.50 (0.48)9
O-Ms  0.562a O-NO2 0.59
O-SiMe3 0.749 - -
S-H 1.229 S- 1.3
S-CN 1.23 S-Me 0.7 (1.1)2a
S-Ph 0.8 - -
S(O)Ph 1.9 S(O)Me 1.2
S(O)2Ph 2.5 S(O)2Me 2.5
Se-Ph 1.13 Te-Ph 0.9
Group A-Value (kcal/mol) Group A-Value (kcal/mol)
NC 0.212a (0.19)9 N=C=O 0.512a
N=C=S 0.282a (0.21)9 N=C=NR2b 1.0
NH2* 1.2-1.7 (1.23)9 NHMe* 1.0
NMe2 2.1 NH3+ 1.9
N3 0.629 NO2 1.052a (1.13)9
PH2 1.64 PMe2 1.54
PCl2 1.94 P(OMe)2 1.54
PMe3+ >3.04 P(S)Me2 >3.04
P(O)Ph2 2.65 - -
SiCl3 0.61 SiMe3 2.56
GeMe3 2.17 GePh3 2.97
SnMe3 1.17 SnPh3 1.47
PbMe3 0.77 - -
HgBr 0.0 HgCl -0.3
HgOAc 0.02a - -
MgBr (Et2O) 0.78 Mg-C6H11 0.53

* Solvent dependent.
General:  Hirsch, Topics in Stereochemistry, 1967, 3, 199;  Jensen, F. R.; Bushweller, C. H. Adv. Alicyclic Chem 1971, 3, 139.  Eliel, E. L.; Wilen, S. H.; Stereochemistry of Organic Compounds, Wiley, 1993, p. 696. Eliel, E. L.; Wilen, S. H.; Doyle, M. P. Basic Organic Stereochemistry, Wiley, 2001, p. 443.
   1. Tetrahedron Lett. 1989, 30, 1059.
   2. By NMR: (a) Jensen F. R.; Bushweller, C. H.; Beck, B. H. J. Am. Chem. Soc. 1969, 91,344. (b) Bushweller, C. H.; O'Neil, J. W. J. Org. Chem. 1970, 35,276.
   3. Tetrahedron Lett. 1985, 26, 1205.
   4. Gordon, M. D.; Quin L. D. J. Am. Chem. Soc. 1976, 98, 15; J. Org. Chem. 1976, 41,1690.
   5. Juaristi, E.; Lopez-Nunez, N. A.; Glass, R. S.; Petsom, A.; Hutchins, R. O.; Stercho, J. P. J. Org. Chem. 1986, 51, 1357.
   6. Kitching, W.; Olszowy, H. A.; Drew, G. M.; Adcock; W. J. Org. Chem. 1982, 47, 5153.
   7. Kitching, W.; Olszowy, H. A.; Harvey, K. J. Org. Chem. 1982, 47, 1893.
   8. Eliel, E. L. J. Org. Chem. 1981, 46, 1959.
   9. Direct observation of 13C signals of axial and equatorial conformers: Schneider, H. J.; Hoppen, V. J. Org. Chem. 1978, 43, 3866.

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H. J. Reich/rev. 02-06