Chelating agents or chelants are compounds having two or more donor atoms that can form cyclic coordination complexes or chelates with acceptor metals. The complexation is an equilibrium reaction that often strongly favors the complex. Chelating is used to modify or control the behavior of metals and their compounds by controlling the concentration of the metals in solution or to utilize the special properties of the chelation compounds. The active groups in chelants may be linear chains, eg, NCCN, macrocyclic rings, eg [OCC] n , or polycyclic structures, such as the cryptates, eg, X[CCYCC) n ] 3 Y, where X and Y are bridgehead and donor atoms, respectively. Some pH, stability, solubility, and electrochemical relationships among simultaneous equilibria in chelation are shown. A broad range of applications based on concentration control, the special properties, and medical uses of chelation compounds are given. Metal sequestration, solubilization, and buffering are discussed as are metal extraction, precipitation, and displacement. Economic data for industrial chelating agents are given. Use of chelating agents is essentially benign environmentally and presents little or no hazard to health or safety under normal conditions of use and handling.

No abstract

No abstract

No abstract