Studies on borate, esters. Part 8. Interactions of cations with oxyacid anion-bridged esters of D-glucarate in alkaline media

Abstract

Cation co-ordination has been studied in aqueous cation–borate–D-glucarate systems using ¹¹B n.m.r. spectroscopy. The univalent cations K^I, Na^I, and Ag^I do not show preferential co-ordination by the borate esters of D-glucarate. The divalent cations Mg^II, Ca^II, Co^II, Ni^II, Sr^II, Cd^II, and Ba^II are co-ordinated by the borate diesters. The cations that ionize the α-hydroxyl functions of D-glucarate, Cu^II, Zn^II Pr^III and Pb^II and/or compete with borate for the diol functions, Al^III and Fe^III, are more strongly co-ordinated by free D-glucarate than by its borate diester. The different behaviour of the cations is discussed in terms of differences in charge/radius density and polarizing ability. In the Ca^II–oxyacid anion–D-glucarate system, Ca^II ion-selective electrode measurements and Ca^II sequestering capacity determinations have been performed. Apart from borate, synergic Ca^II co-ordination is observed at high pH for the oxyacid anion esters of D-glucarate of antimonite, stannate, aluminate, and germanate.