AC POLAROGRAPHIC-DETERMINATION OF THE RATE OF ION TRANSFER FOR A SERIES OF ALKYLAMMONIUM IONS AT THE NITROBENZENE WATER INTERFACE

The rate of ion transfer across the polarized nitrobenzene/water interface has been determined for twelve homologous alkylammonium ions by using phase-selective ac polarography. A new cell with a two-electrode configuration was used to minimize the interference arising from the non-ideal behaviour of the non-polarized nitrobenzene/water interface. Compensation of the iR drop by means of a positive feedback method has been proven to be useful for obtaining reliable kinetic parameters. The apparent standard rate constants, K(s), for all alkylammonium ions were of the order of 0.1 cm s-1. k(s) increased slightly with increasing ionic radius from trimethylammonium ion to tetraethylammonium ion and then decreased with a further increase in the radius to tetrapropylammonium ion. This dependence of k(s) on the ionic radius suggest that, in the ion transfer of smaller alkylammonium ions, the desolvation-resolvation process is involved in the rate-determining step, whereas the effect of hydrodynamic friction prevails for larger alkylammonium ions.