A sodium-specific condensed film of alpha-cyclodextrin at the mercury vertical bar water interface

alpha-Cyclodextrin adsorption at the mercury \ water interface exhibits sev eral condensed phases, depending on the anions and cations present. At low charge densities the interface can be covered by a condensed film of alpha- cyclodextrin. In the presence of sodium ions, a condensed film containing b oth alpha-cyclodextrin and Na+ can be observed at a negatively charged elec trode. This highly sodium-specific film contains three alpha-cyclodextrin m olecules for every two Naf cations, and can be characterized by the interfa cial solubility product [alpha CD](3)[Na+](2) = 1.65 x 10(-6) M-5 at 25 deg rees C. This film exhibits isomer-specific inhibition of reduction processe s; its formation can be stochastic. (C) 1999 Elsevier Science S.A. All righ ts reserved.