Second moment in wide-line proton magnetic resonance and its relation to packing density of protons in the unit cell

Analysis of the proton magnetic resonance second moment data of more than 60 organic and biological compounds has been carried out. It is shown that with certain classification schemes, such as compounds involving groups of protons (triplets and doublets), the second moment exhibits an approximate linear correlation with the proton density in the unit cell, defined as the number of protons per unit volume in the particular packing adopted by the structure.