Comparison of the polographic behavior of the Cd2+-glycine, N-acetyl- and N-benzoyl-glycine systems in aqueous and ethanolic solution

✍ Scribed by G.Battistuzzi Gavioli; L. Benedetti; G. Grandi; G. Marcotrigiano; G.C. Pellacani; M. Tonelli

• Publisher: Elsevier Science
• Year: 1979
• Tongue: English
• Weight: 433 KB
• Volume: 37
• Category: Article
• ISSN: 0020-1693
• DOI: 10.1016/s0020-1693(00)95511-7

✦ Synopsis

The complexation reactions of glycine, N-ace@and N-benzoyl-glycine with the Cd" ion were studied as a model for metal-protein intemctions, using polarographic techniques in aqueous and ethanolic solution at 0.1 M NaC104, as base electrolyte, to identify the number and type of solution complex species and to calculate their stability constants. In aqueous solution three complexes of the forms CdL', CdL2 and CdL; coexist in the pH range 7-10 for the glycine, while the N-protected amino acids do not react under any pH conditions. In ethanolic solo tion four complexes of the forms CdL', CdL2, CdLS and CdL:-coexist for the N-protected amino acids, while for the glycine the CdL:-complex prevails. A Hammett relationship is observed between the reversible Ey2 or &, (stability constant) values versus the a constants for the substituents on the amino group. A coordinative hypothesis for the complexes in solution is also suggested.