Protonation microequilibrium treatment of polybasic compounds with any possible symmetry

Microequilibrium treatment that has previously been limited to tridentate l igands is generalized to arbitrary number of functional groups in the molec ule and the role of symmetry is also investigated. Cumulative microconstant , a new type of equilibrium parameter, is introduced, allowing an equivalen t, but more compact mathematical treatment of large microequilibrium system s. The sufficient number of independent pieces of information for the unamb iguous determination of all microconstants is deduced. It has been conclude d that even if protonation mole fraction for all the basic sites is availab le, determinability of all the microconstants is rather the exception than the case, without a priori simplifying assumptions. It has been shown that all microconstants can only be determined from protonation mole fractions f or molecules of up to three groups. For molecules of four groups and beyond , only specific symmetry and the concomitant simplification of the microequ ilibrium system make the strict, complete microspeciation feasible. As a ca se study, the protonation scheme and the complete microspeciation of a tetr adentate ligand is analyzed in detail.