DIMERCAPROL
Formula: C3H8OS2
IUPAC Name: 2,3-Dimercaptopropan-1-ol
Other Names: 2,3-dimercapto-1-propanol, British Anti-Lewisite (BAL)
Introduction
Dimercaprol is an important medicine used to remove poisonous heavy metals from the body. It contains two sulfhydryl (–SH) groups placed next to each other. These groups help it bind toxic metals like arsenic, mercury, lead, and gold. Because of this strong binding ability, Dimercaprol works as a chelating agent.
Preparation of Dimercaprol
Dimercaprol is prepared in two main steps:
- Bromination of allyl alcohol – This reaction produces 2,3-dibromopropanol (via electrophilic addition).
- Reaction with sodium sulfhydrate – The bromine atoms get replaced by sulfhydryl (–SH) groups, producing Dimercaprol.
The presence of two –SH groups makes Dimercaprol very reactive and useful in oxidation-reduction and metal-binding reactions.
Tests for Purity
- Appearance: Clear, colorless liquid
- pH: 5.0 – 6.5 (slightly acidic)
- Refractive Index: 1.568 – 1.574 (1% solution at 20°C)
- Density: 1.238 – 1.240 g/mL
- Iron: Less than 20 ppm
- Halides: Less than 500 ppm
Assay (How Purity Is Measured)
The purity of Dimercaprol is measured by an iodometric titration. It reacts with iodine in an acidic medium. The sulfhydryl groups release hydrogen, forming hydrogen iodide, and the remaining iodine is measured using a starch indicator.
Conversion factor: 1 mL of 0.05 M iodine ≡ 0.0621 g of Dimercaprol
Uses of Dimercaprol
Dimercaprol is widely used as an antidote for heavy metal poisoning. Its main uses include:
- Treatment of arsenic, gold, and mercury poisoning
- Used along with EDTA to treat lead poisoning
- Used in conditions like Wilson’s disease (a disorder where excess copper accumulates in the body)
- Acts as a general chelating agent for metals like Ni and Sb
Note: Dimercaprol is a strong and essential antidote; however, it must be used cautiously under medical supervision.
Detailed Notes:
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