No abstract

D], 9 [A], and [D], < [A], was shown to be reasonable.15 Very recently, however, it has been possible to obtain some values of K from n.m.r. measurements under the condition [D], = [A],.16 Some of these values differ by ca. 100% from those obtained from n.m.r. data on systems in which [D], > [A],.Although the first n.m.r. determinations of K using measurements from two non-equivalent nuclei yielded consistent results,17 Klinck and Stothers l8 reported that

The four acid dissociation constants of the DOPA cation have been determined at 25' f 0.02" and 1 .OM ionic strength (KN03) by means of a glass-calomel electrode system. The reactions of the ligand with copper(l1) ions were also examined by potentiometric methods by use of both glass and copper amalgam electrodes, and the polymerisation of copper-DOPA complexes has been studied. Stability constants (measured at 25" f 0.02" and 1 .OM ionic strength) for the copper complexes have been measured for both chelating sites and the dimerization constant obtained. The implications of these results with regard to metal-catalysed oxidations of catechol derivatives are discussed.

No abstract

The four acid dissociation constants of the 3,4-dihydroxyphenylglycine (DOPG) cation have been determined at 25" f 0.01 and 1 .OM ionic strength (KNO,) by means of a glass-calomel electrode system. The reactions of the ligand with copper(l1) ions were also examined by pH methods: polymer formation and ligand exchange reactions have been observed and the behaviour of this system compared with reactions of related ligands. Stability constants for the copper complexes and for the formation of a tetramer are reported.