Molecular interactions and reorientational motion of neat acetone in the liquid state. 17O NMR chemical shifts and linewidths at variable temperature

The structure and dynamics of neat liquid acetone have been studied in the 181–325 K temperature range by ¹⁷O NMR. The chemical shift data are consistent with a monomer—dimer equilibrium; the standard enthalpy and entropy of association for the acetone dimer are ?1.1 kcal/mol and ?8.5 cal mol^?1 K^?1, respectively. From the linewidth measurement, it seems that the dimer is only a short-lived electrostatic-collided complex which does not reorient as a whole: rotational motion of the oblate spheroid acetone is found to fit the hydrodynamic equation under “slip” boundary conditions.