Synthesis and study of properties of d,l-N,N-N'N'-tetracarboxymethyl-α,β-diaminopropionic acid

A scheme for the synthesis of a new complexone-d,l-N,N-N'N'-tetracarboxylmethyl-α,β-diaminopropionic acid (HEDTA) representing a pentabasic acid (H5L) is provided, and its complexing with Cd2+ ions is studied. It is shown that in the case of pH 3-5.5 a complex is formed with the component ratio Cd2+:H5L=2:1. A stability constant of this complex has been found by potentiometry and polarography, it being 14.50 and 14.19, respectively. The dissociation constant of HEDTA -pK, pK2, pK3, pK4 and pK5 is 0.5, 1.8, 2.2, 6.2 and 9.7. HEDTA will also complex with Ca2+, Sr2+, Cd2+, Zn2+, Pb2+, Hg2+ ions, it is a stronger acid as compared with EDTA and may be used in analytical chemistry