ABSTRACT
The composition and stability constants of the complexes formed between Ni(2+) and Zn(2+) and 3-mercaptopropionic acid (3-MPA) were studied by a potentiometric method at 25 degrees and in 0.5M KNO(3). For the system Zn(2+)/3-MPA. a mixture of the mononuclear complex BA(2) and the polynuclear complexes B(3)A(4). and B(4)A(6) was found (B means the metal ion and A the ligand). The system Ni(2+)/3-MPA can be represented by the complexes B(5)A(10), B(6)A(11) B(6)A(9) and B(6)A(12). In this series the last two complexes are predominant.
ABSTRACT
The microscopic acidity constants of the diprotonated asymmetric N-methyl-substituted ethylenediamines and N-methylpiperazine were determined by using the change of the chemical shift of the methyl protons with varying acidity. The determination was carried out at 25 degrees in aqueous solution and in an ionic medium of 1M KNO(3). The basicity of the amino-functions follows the expected sequence: secondary > primary 2 > tertiary. The influence of the substituent on the basicity of the end-group is primary > secondary 2 > tertiary.
