The chelating ligand used for the treatment of lead poisoning is :
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It is a hexadentate ligand, and its high stability is attributed to the "Chelate Effect," where multidentate ligands form more stable complexes than monodentate ones.
- Ethane-1,2-diamine
- Oxalate ion
- Dimethylglyoxime
- EDTA
The Correct Option is D
Solution and Explanation
• Chelation therapy is a medical procedure used to remove heavy metals like lead (\( Pb \)), mercury, or arsenic from the bloodstream.
• It involves the administration of chelating agents (ligands) that bind to metal ions to form stable, cyclic coordination complexes.
• These complexes are water-soluble and can be easily excreted by the kidneys through urine.
• The effectiveness of a chelator depends on its denticity and the stability constant of the resulting complex.
Step 1: Analyze the characteristics of the options
(A) Ethane-1,2-diamine (en): A bidentate ligand with 2 nitrogen donor atoms.
(B) Oxalate ion (\( ox \)): A bidentate ligand with 2 oxygen donor atoms.
(C) Dimethylglyoxime (DMG): A bidentate ligand often used specifically for Nickel (\( Ni^{2+} \)) detection.
(D) EDTA (Ethylenediaminetetraacetate): A hexadentate ligand with 6 donor atoms (2 Nitrogen and 4 Oxygen).
Step 2: Evaluate EDTA's structure and binding
EDTA is a powerful chelating agent because it can "envelop" a metal ion by binding at six different sites simultaneously.
This creates a very stable cage-like structure around the toxic metal ion.
Step 3: Explain the clinical treatment mechanism
For lead poisoning, a specific salt called Calcium disodium EDTA (\( CaNa_{2}EDTA \)) is used.
In the body, the lead ion (\( Pb^{2+} \)) has a much higher affinity for EDTA than the calcium ion (\( Ca^{2+} \)).
The lead ions displace the calcium ions from the EDTA complex:
\[ [Ca(EDTA)]^{2-} + Pb^{2+} \rightarrow [Pb(EDTA)]^{2-} + Ca^{2+} \]
Step 4: Conclusion
The resulting \( [Pb(EDTA)]^{2-} \) complex is extremely stable and non-toxic, which is then safely excreted from the patient's body.
Thus, EDTA is the preferred ligand for treating lead poisoning.
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