Question

MTBE, the solvent in the above procedure, is a good solvent for liquid-liquid extractions.

What are the characteristics of a good solvent for liquid-liquid extractions?

Answer 1

In liquid-liquid extraction, solid compounds are usually separated from impurities by dissolving the compounds in a mixture of two immiscible liquids or solvents. Usually, water is one of the solvents used in the extraction process. The other solvent is usually an organic compound having a low polarity like hexane, dichloromethane, ether, etc.

One of the vital properties of the solvent used in the extraction is that the solvent must have low polarity as compared to water. The organic solvent must not interact with water and must form a separate layer with water.

The solvent must have a high solubility for the target compound. In case of organic solids, the solvent is so chosen that the compound dissolves completely in the solvent and the impurities (usually water-soluble compounds) have very poor solubility in the organic solvent. This also implies that the solvent must not dissolve the impurities appreciably.

The organic solvent must be volatile and easily removed from the solid compound by distillation.

The solvent must be non-toxic and cheap so that the extraction process is commercially viable.