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, 1.688
C≡N 0.17, 0.242a, 0.219 C≡C-H 0.412a, 0.529
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, 1.312a 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, 0.282a, 0.369 Cl 0.43, 0.532a, 0.519
Br 0.38, 0.482a9 I 0.43, 0.472a, 0.499
O-Me 0.60, 0.759 O-CD3 0.56, 0.552a
O-Et 0.9 O-H* 0.87, 1.09
O-Ac 0.6, 0.712a, 0.799 O-C(=O)CF3 0.68, 0.589
O-CHO 0.27, 0.592a, 0.629 O-Ts 0.50, o.522a, 0.489
O-Ms  0.562a O-NO2 0.59
O-SiMe3 0.749, 1.3110, 0.8011 O-SiiPr3 0.519, 0.9410
O-SiMe2tBu 1.0610 O-SiPh2tBu 0.5610
S-H 1.172a, 1.229 S- 1.3
S-C≡N 1.232a S-Me 0.7, 1.072a, 1.12a
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, 0.199 N=C=O 0.512a
N=C=S 0.282a, 0.219 N=C=NR2b 1.0
NH2* 1.2-1.7, 1.239 NHMe* 1.0
NMe2 2.1 NH3+ 1.9
NHSiMe3 1.2111
N3 0.629 NO2 1.052a, 1.139
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 0.612a 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) 0.782c Mg-C6H11 0.532c

* 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 direct NMR observation of 1H signals of axial and equatorial conformers at low-temperature: (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. (c) In ether: Jensen F. R.; Nakamaye, K. L J. Am. Chem. Soc. 1968, 90,3248.
   3. Duddeck, H.; Wagner, P.; Gegner, S. 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 NMR signals of axial and equatorial conformers in toluene-d8: Schneider, H. J.; Hoppen, V. J. Org. Chem. 1978, 43, 3866.
   10. (a) The A-values for OSiR3 are unusually sensitive to solvent. These values in CD2Cl2 from low-temperature 13C NMR: Eliel, E. L.; Satici, H. J. Org. Chem. 1994, 59, 688. (b) Marzabadi, C. H.; Anderson, J. E.; Gonzalez-Outeirino, J.; Gaffney, P. R. J; White, C. G. H; Tocher, D. A.; Todaro, L. J. J. Am. Chem. Soc. 2003, 125,15163.
   11. Hardy, J. P.; Cumming, W. D. J. Am. Chem. Soc. 1971, 93, 928.



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