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What kind of properties are required for an extraction solvent?
The extracting solvent must be immiscible with the solution to be extracted.
WATER or a water-based solution is usually one of the pair. The other solvent is an ORGANIC SOLVENT .What organic solvents are immiscible with water?---- Here is the general rule:
The more polar the organic solvent, the more it is miscible (soluble) with water.
For example, polar solvents such as methanol, ethanol and acetone are miscible with water, thus not suitable for liquid-liquid extraction.
Organic solvents with low polarity such as hexanes, toluene, dichloromethane and diethyl ether are usually chosen as the organic extracting solvent.
The compound(s) to be extracted, which are present in a solution, should also be soluble in the extracting solvent.
Major impurities (e.g., from a reaction) should not be soluble in the extracting solvent.
The extracting solvent should be sufficiently volatile so that it can be removed easily from the extracted material by distillation.
It is usually desirable if the solvent is non-toxic and not flammable.
Unfortunately, few solvents are known to meet both criteria...
- Some solvents are not toxic but flammable (e.g., diethyl ether, hydrocarbons--petroleum ether, hexanes).
- Some are not flammable but toxic (e.g., dichloromethane, chloroform).
- Some solvents are both toxic and flammable (e.g., benzene).
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Organic Web Chem University of Alberta
