Determination of Molecular Torsion Angles Using Nuclear Singlet Relaxation

The exponential relaxation time constant, T(S), of a nuclear singlet state is influenced by the proximity of neighboring NMR-active nuclei. For methylene groups in particular this dependence is much stronger than the case for other NMR relaxation constants, including the "conventional" relaxation time constant, T(1), of the longitudinal magnetization. This sensitivity provides a new route for determining torsional angles plus other molecular structural details in the isotropic solution phase.