Application of 1 H NMR bi‐selective relaxation times to conformational analysis in solution

The usefulness of 1 H bi‐selective relaxation times ( T   1 BS ) and selective relaxation times ( T   1 s ) for structure and conformation determination is emphasized. A pulse sequence has been devised which provides the apparent observed T   1 BS . The cross‐relaxations (σ ij ) or F ij values are derived from the observed T   1 BSand T   1 Svalues. The σ ij values can be correlated with the HH distances ( r ij ) and can be used for conformational analysis or structure determination. The F ij values, which indicate the fractional contribution to the dipolar relaxation of proton i via the interaction with proton j ( i ≠ j ), can be compared with the NOE values. 2‐Vinylpyridine was chosen as a model compound and three types of T 1 values were measured for its protons. Its conformation in CDCl 3 solution is discussed based on the correlation between the σ ij obtained and the r ij values. A conformational equilibrium is suggested.