Coupling Constants in Rigid Five-Membered Rings: N.M.R. Spectra of the Camphane-2,3-Diols

The proton nuclear magnetic resonance (N.M.R.) spectra of the four diastereoisomers of camphane-2,3-diol are reported. The coupling constants between the 2-, 3-, and 4-protons agree with the values predicted by Karplus for ethane derivatives. In particular, the cis (0° dihedral angle) coupling constants (7.7 and 8.9 c.p.s.) are much larger than the trans (120° dihedral angle) coupling constants (2.2 and 2.3 c.p.s.). Unexpected 1,3-coupling between exo-hydrogen atoms occurs in some of the compounds studied.