The dipole moments of some tri-n-butylammonium and triethylammonium salts in benzene solution

Abstract

The dielectric constants, specific volumes, and refractive indices of dilute benzene solutions of the title salts have been measured at 25° and their dipole moments deduced. Comparison of the results with the moments, when known, of the corresponding quaternary ammonium salts indicates that the salts of the strongest acids exist essentially in the form of ion-pairs in which there is probably hydrogen bonding between the cation and anion. The salts of the weakest acids probably exist as hydrogen-bonded complexes in which no formal charge-transfer has occurred. The salts of acids with pK_a values, in aqueous solution, between about 2 and 4 have dipole moments which are intermediate between the values expected for these extreme states. Preliminary evidence from infrared spectroscopy suggests that in some of these cases the two forms may co-exist in equilibrium.