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Dichloromethane (DCM): The Essential Extraction Solvent
Why Methylene Chloride is the "sinking" alternative to ether in the separatory funnel.
Molecular Blueprint: CH2Cl2
Dichloromethane, commonly known as DCM or Methylene Chloride, is a geminal organochloride. It is a colorless, volatile liquid with a moderately sweet aroma. Its high density and low boiling point make it one of the most useful solvents in organic chemistry.
- Boiling Point: 39.6°C (Extremely easy to remove)
- Density: 1.33 g/cm³ (Heavier than water)
- Flammability: Non-flammable (Unlike Diethyl Ether)
The Density Rule: DCM vs. Ether
In a liquid-liquid extraction (using a separatory funnel), identifying your organic layer is critical.
This density difference is a frequent "trick question" in lab practicals. Always double-check the density before draining your funnel!
Practical Advantages
Easy Evaporation
With a boiling point of only 40°C, DCM can be removed from a product at room temperature using a rotovap. This is ideal for heat-sensitive organic compounds.
Safety Over Ether
Unlike Diethyl Ether, DCM is not highly flammable and does not form explosive peroxides. This makes it a much safer choice for large-scale extractions.
Toxicity and Handling
DCM is not without risks. It is a potential carcinogen and can be metabolized to carbon monoxide in the body if inhaled.
Funnel Intelligence
You are extracting an aqueous solution with Dichloromethane. Which layer do you keep if your organic product is dissolved in the DCM?
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