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

A new method is described for the accurate measurement of quadrupole coupli ng parameters in liquids. Both experimental and theoretical data are given and show that for the OD deuteron in methanol the deuterium quadrupole coup ling parameter chi(D) is related to the deuterium chemical shift delta(D) b y the equation chi(D) = 284 - 15.3 delta(D); the R-2 value for this correla tion is 0.99. The straightforward measurement of delta(D) provides an accur ate value for chi(D) which in turn provides a value for the molecular corre lation time. This methodology is applied to the measurement of the methanol correlation times as a function of concentration for the methanol/CCl4 sys tem. The molecular correlation time along with a value for the solution vis cosity provide an estimate of the average size for the methanol clusters pr esent in the solution. The data reported here indicate that the average vol ume for the methanol clusters present in neat methanol is about 230 Angstro m(3), a value about midway between the volume for a cyclic pentamer (215 An gstrom(3)) and a cyclic hexamer (242 Angstrom(3)).