An indirect method for the measurement of deuterium quadrupole coupling constants in liquids

A new method is described for the accurate measurement of quadrupole coupling parameters in liquids. Both experimental and theoretical data are given and show that for the OD deuteron in methanol the deuterium quadrupole coupling parameter χD is related to the deuterium chemical shift δD by the equation χD = 284—15.3δD; the R 2 value for this correlation is 0.99. The straightforward measurement of δD provides an accurate value for χD which in turn provides a value for the molecular correlation time. This methodology is applied to the measurement of the methanol correlation times as a function of concentration for the methanol/CCl4 system. The molecular correlation time along with a value for the solution viscosity provide an estimate of the average size for the methanol clusters present in the solution. The data reported here indicate that the average volume for the methanol clusters present in neat methanol is about 230 Å3, a value about midway between the volume for a cyclic pentamer (215 Å3) and a cyclic hexamer (242 Å3).